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Human Physiology - Respiration, Circulation and Excretion PYQs – Biology, SSC & Railway

159 Human Physiology - Respiration, Circulation and Excretion (Biology) questions asked in recent SSC and Railway exams, newest first, with exam, date & shift, answers and solutions.

📚 159 questionsSSC 49 · Railway 110
12
RRB Group D 2025-26 – 25 August 2026 Shift 2 · Blood vessels, circulation and blood pressure

Q1. Which of the following best describes systolic pressure?

  1. (a) Blood pressure in veins during contraction
  2. (b) Blood pressure in artery during ventricular contraction
  3. (c) Blood pressure in veins during relaxation
  4. (d) Blood pressure in artery during ventricular relaxation
Answer & solution

Answer: (b) Blood pressure in artery during ventricular contraction

Correct Answer:
Correct Answer: Option 2 – Blood pressure in artery during ventricular contraction
Explanation:
Systolic pressureis the pressure exerted by blood on the walls of the arteries when the ventricles of the heartcontract(systole) and pump blood out. It is the higher of the two blood pressure readings (the lower one, diastolic pressure, occurs during ventricular relaxation).
RRB Group D 2025-26 – 25 August 2026 Shift 2 · Lymphatic system

Q2. Which statement CORRECTLY compares the protein content of lymph and blood plasma?

  1. (a) Lymph contains equal protein to plasma
  2. (b) Lymph contains more protein than plasma
  3. (c) Lymph contains less protein than plasma
  4. (d) Lymph contains no protein
Answer & solution

Answer: (c) Lymph contains less protein than plasma

Correct Answer:
Correct Answer: Option 3 – Lymph contains less protein than plasma
Explanation:
Lymph is formed from blood plasma that filters out of capillaries into the tissue spaces. During this filtration, large plasma proteins are largelyretained in the blood(they cannot easily cross capillary walls), solymph contains a much lower protein concentration than blood plasma, along with similar composition otherwise (water, glucose, salts, WBCs).
RRB Group D 2025-26 – 25 August 2026 Shift 3 · Excretory system - kidney and nephron

Q3. What determines how much water is re-absorbed during urine formation?

  1. (a) Excess water
  2. (b) Glucose
  3. (c) Protein
  4. (d) Oxygen
Answer & solution

Answer: (a) Excess water

Correct Answer:
Correct Answer: Option 1 – Excess water
Explanation:
During urine formation, the amount of water reabsorbed back into the blood in the kidney tubules depends on how much excess water is present in the body and how much dissolved waste needs to be excreted — this regulates whether urine is more dilute or more concentrated.
Important Facts:
• This process occurs mainly in the nephron, especially in the loop of Henle and collecting duct.
• Hormones like ADH (antidiuretic hormone) help regulate water reabsorption based on body hydration status.
RRB Group D 2025-26 – 21 August 2026 Shift 1 · Blood vessels, circulation and blood pressure

Q4. Select the correct option regarding the following two statements labelled Assertion (A) and Reason (R).Assertion (A): The walls of veins are thinner than those of arteries.Reason (R): Veins carry blood under high pressure.

  1. (a) Both A and R are true, and R is the correct explanation of A
  2. (b) A is false, but R is true
  3. (c) Both A and R are true, but R is not the correct explanation of A
  4. (d) A is true, but R is false
Answer & solution

Answer: (d) A is true, but R is false

Explanation:
Assertion (A) is true: vein walls are indeed thinner than artery walls, since veins do not need to withstand high pressure. Reason (R) is false: veins carry deoxygenated blood back to the heart under low pressure (arteries carry blood under high pressure). Hence A is true but R is false.
Correct Answer: Option 4 – A is true, but R is false
RRB Group D 2025-26 – 21 August 2026 Shift 2 · Blood vessels, circulation and blood pressure

Q5. In double circulation, which vessel delivers oxygenated blood to the heart?

  1. (a) Pulmonary vein
  2. (b) Pulmonary artery
  3. (c) Vena cava
  4. (d) Aorta
Answer & solution

Answer: (a) Pulmonary vein

Correct Answer:
Correct Answer: Option 1 – Pulmonary vein
Explanation:
The pulmonary vein carries oxygenated blood from the lungs back to the left atrium of the heart — the only vein in the body that carries oxygen-rich blood. The pulmonary artery carries deoxygenated blood away from the heart to the lungs.
RRB Group D 2025-26 – 21 August 2026 Shift 2 · Blood - components and functions

Q6. Oxygen is transported in human blood mainly by binding with the pigment __________.

  1. (a) Haemoglobin
  2. (b) Plasma
  3. (c) Myoglobin
  4. (d) Chlorophyll
Answer & solution

Answer: (a) Haemoglobin

Correct Answer:
Correct Answer: Option 1 – Haemoglobin
Explanation:
Haemoglobin, the iron-containing pigment present in red blood cells, binds reversibly with oxygen to form oxyhaemoglobin, enabling efficient transport of oxygen from the lungs to body tissues.
RRB Group D 2025-26 – 21 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q7. What are the end products formed during anaerobic respiration in yeast cells?

  1. (a) Water and oxygen
  2. (b) Glucose and oxygen
  3. (c) Lactic acid and water
  4. (d) Ethanol and carbon dioxide
Answer & solution

Answer: (d) Ethanol and carbon dioxide

Correct Answer:
Correct Answer: Option 4 – Ethanol and carbon dioxide
Explanation:
In yeast, anaerobic respiration (fermentation) converts glucose intoethanol and carbon dioxide, releasing a small amount of energy.
Important Facts:
• In muscle cells during vigorous exercise (anaerobic respiration), the end product is lactic acid instead.
• Aerobic respiration produces CO2 and water as end products.
RRB Group D 2025-26 – 21 August 2026 Shift 3 · Respiration and excretion in other organisms

Q8. A field ecologist studies fish in a high-altitude lake with low oxygen. Which structural adaptation in the gills would most likely be observed?

  1. (a) Thicker gill membranes
  2. (b) Fewer capillaries in gill tissue
  3. (c) Reduced blood flow in gills
  4. (d) Greater surface area for gas exchange
Answer & solution

Answer: (d) Greater surface area for gas exchange

Correct Answer:
Correct Answer: Option 4 – Greater surface area for gas exchange
Explanation:
In low-oxygen (high-altitude) water, fish gills adapt by increasing thesurface areaavailable for gas exchange (more/larger gill lamellae), maximizing oxygen uptake from scarce dissolved oxygen.
Important Facts:
• Thinner gill membranes (not thicker) and greater blood flow/capillary density also aid gas exchange, opposite of the incorrect options given.
RRB Group D 2025-26 – 21 August 2026 Shift 3 · Dialysis and other excretory organs

Q9. Match the excretory product in Column A with the organ that removes it in Column B.
[TABLE]
Column A (Excretory Product) | Column B (Organ)
(a) Urea | (i) Liver
(b) Carbon dioxide | (ii) Lungs
(c) Excess salts | (iii) Skin
(d) Bile salts | (iv) Kidney
[/TABLE]

  1. (a) a–iv, b–iii, c–i, d–ii
  2. (b) a–iv, b–ii, c–iii, d–i
  3. (c) a–ii, b–i, c–iv, d–iii
  4. (d) a–iii, b–iv, c–ii, d–i
Answer & solution

Answer: (b) a–iv, b–ii, c–iii, d–i

Correct Answer:
Correct Answer: Option 2 – a–iv, b–ii, c–iii, d–i
Explanation:
Matching each excretory product with the organ that removes it:
• a. Urea → iv. Kidney
• b. Carbon dioxide → ii. Lungs
• c. Excess salts → iii. Skin (via sweat)
• d. Bile salts → i. Liver (bile is produced/processed by the liver)
Important Facts:
• Kidneys remove nitrogenous waste (urea) by filtering blood.
• Skin removes excess water and salts through sweat.
RRB Group D 2025-26 – 21 August 2026 Shift 3 · Blood - components and functions

Q10. The absence of a nucleus in mature RBCs provides more room for __________, which carries oxygen to the body.

  1. (a) Lysosomes
  2. (b) DNA
  3. (c) Chlorophyll
  4. (d) Hemoglobin
Answer & solution

Answer: (d) Hemoglobin

Correct Answer:
Correct Answer: Option 4 – Hemoglobin
Explanation:
Mature mammalian RBCs lack a nucleus, which creates more internal space to be packed withhemoglobin, the oxygen-carrying pigment, maximizing oxygen-carrying capacity.
Important Facts:
• The absence of a nucleus also gives RBCs their characteristic biconcave shape, increasing surface area for gas exchange.
RRB Group D 2025-26 – 21 August 2026 Shift 3 · Human respiratory system

Q11. Match Column A with Column B .
[TABLE]
| Column A | | Column B
(a) | Alveoli | (i) | Prevents food entry into the trachea
(b) | Haemoglobin | (ii) | Gas exchange
(c) | Diaphragm | (iii) | Oxygen transport
(d) | Epiglottis | (iv) | Helps in inhalation
[/TABLE]

  1. (a) a–iii, b–ii, c–iv, d–i
  2. (b) a–ii, b–iv, c–iii, d–i
  3. (c) a–iv, b–iii, c–ii, d–i
  4. (d) a–ii, b–iii, c–iv, d–i
Answer & solution

Answer: (d) a–ii, b–iii, c–iv, d–i

Correct Answer:
Correct Answer: Option 4 – a–ii, b–iii, c–iv, d–i
Explanation:
Matching each structure with its function:
• a. Alveoli → ii. Gas exchange
• b. Haemoglobin → iii. Oxygen transport
• c. Diaphragm → iv. Helps in inhalation
• d. Epiglottis → i. Prevents food entry into the trachea
Important Facts:
• The diaphragm contracts and flattens during inhalation, increasing thoracic cavity volume.
• The epiglottis is a flap of cartilage that covers the windpipe during swallowing.
RRB Group D 2025-26 – 20 August 2026 Shift 1 · Excretory system - kidney and nephron

Q12. Which of these structures carries urine from the kidneys to the bladder?

  1. (a) Urethra
  2. (b) Ureters
  3. (c) Trachea
  4. (d) Intestines
Answer & solution

Answer: (b) Ureters

Correct Answer:
Correct Answer: Option 2 – Ureters
Explanation:
Theuretersare muscular tubes that carry urine from each kidney to the urinary bladder. Theurethracarries urine out of the body from the bladder.
Important Facts:
• Kidney → Ureter → Bladder → Urethra is the path of urine.
• Trachea is part of the respiratory system, not the excretory system.
• Intestines are part of the digestive system.
RRB Group D 2025-26 – 20 August 2026 Shift 1 · Aerobic and anaerobic respiration

Q13. Select the correct option regarding the following two statements labelled Assertion (A) and Reason (R).Assertion (A): Carbon dioxide is a reactant in aerobic respiration.Reason (R): Carbon dioxide is released during the oxidation of glucose.

  1. (a) A is true, but R is false
  2. (b) A is false, but R is true
  3. (c) Both A and R are true but R is not the correct explanation of A
  4. (d) Both A and R are true, and R is the correct explanation of A
Answer & solution

Answer: (b) A is false, but R is true

Correct Answer:
Correct Answer: Option 2 – A is false, but R is true
Explanation:
Assertion:Carbon dioxide is a reactant in aerobic respiration — this isfalse. In aerobic respiration, glucose andoxygen
are the reactants, while carbon dioxide and water are the products.Reason:Carbon dioxide is released during the oxidation of glucose — this istrue, as CO₂ is indeed a by-product of glucose oxidation during respiration.
Important Facts:
• Aerobic respiration equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy.
• Oxygen is consumed (reactant); carbon dioxide and water are released (products).
RRB Group D 2025-26 – 20 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q14. The amount of energy released during aerobic respiration in animals is _____ that released during anaerobic respiration.

  1. (a) Slower than
  2. (b) Greater than
  3. (c) Equal to
  4. (d) Lesser than
Answer & solution

Answer: (b) Greater than

Correct Answer:
Option 2 – Greater than
Explanation:
Aerobic respiration completely oxidizes glucose using oxygen (yielding CO₂ and H₂O), releasing farmore energy(about 38 ATP) compared to anaerobic respiration, which only partially breaks down glucose (yielding about 2 ATP) without oxygen.
RRB Group D 2025-26 – 19 August 2026 Shift 1 · Excretory system - kidney and nephron

Q15. Which organ directly filters nitrogenous waste from human blood?

  1. (a) Liver
  2. (b) Lungs
  3. (c) Kidneys
  4. (d) Heart
Answer & solution

Answer: (c) Kidneys

Correct Answer:
Correct Answer: Option 3 – Kidneys
Explanation:
Thekidneysfilter nitrogenous wastes (like urea, uric acid, and creatinine) directly from the blood through structural/functional units callednephrons, forming urine that is eventually excreted.
Important Facts:
• The functional unit of the kidney is the nephron.
• The liver produces urea (from ammonia) but does not filter it from blood — that is the kidney's role.
• Lungs remove CO₂, not nitrogenous waste.
RRB Group D 2025-26 – 19 August 2026 Shift 2 · Blood vessels, circulation and blood pressure

Q16. What prevents blood from flowing backward inside the low-pressure veins of the human circulatory system?

  1. (a) Microscopic capillaries
  2. (b) One-way valves
  3. (c) High pumping force
  4. (d) Thick elastic walls
Answer & solution

Answer: (b) One-way valves

Correct Answer:
Correct Answer: Option 2 – One-way valves
Explanation:
Veins carry blood back to the heart at low pressure. To prevent the backflow of blood (especially against gravity in limbs), veins containone-way (semilunar) valvesthat allow blood to flow only toward the heart.
Important Facts:
• Arteries, which carry high-pressure blood away from the heart, do not need such valves (except the semilunar valves at the heart's exit points).
• Valve failure in veins can lead to conditions like varicose veins.
RRB Group D 2025-26 – 19 August 2026 Shift 2 · Heart - structure and functioning

Q17. In mammals, what is the primary advantage of having a four-chambered heart in relation to the transportation of blood in the lungs?

  1. (a) Prevents mixing of oxygenated and deoxygenated blood
  2. (b) Reduces blood pressure in the lungs
  3. (c) It ensures only oxygenated blood enters the lung tissue
  4. (d) Allows blood to flow only once through the heart
Answer & solution

Answer: (a) Prevents mixing of oxygenated and deoxygenated blood

Correct Answer:
Correct Answer: Option 1 – Prevents mixing of oxygenated and deoxygenated blood
Explanation:
A four-chambered heart (two atria, two ventricles) completely separates the pulmonary circuit (deoxygenated blood to lungs) from the systemic circuit (oxygenated blood to body). This complete separationprevents mixing of oxygenated and deoxygenated blood, ensuring highly efficient oxygen delivery to tissues — important for the high metabolic rate of mammals (endothermy).
Important Facts:
• Deoxygenated blood (not oxygenated) is what enters the lungs to be oxygenated, so option 3 is factually wrong.
• Two-chambered (fish) and three-chambered (most reptiles/amphibians) hearts allow some mixing of blood.
RRB Group D 2025-26 – 19 August 2026 Shift 3 · Blood vessels, circulation and blood pressure

Q18. Select the correct option regarding the following two statements labelled Assertion (A) and Reason (R).Assertion (A): Blood pressure increases temporarily during exercise.Reason (R): Exercise increases heart rate and the volume of blood pumped by the heart per minute.

  1. (a) Both A and R are true, and R is the correct explanation of A
  2. (b) Both A and R are true, but R is not the correct explanation of A
  3. (c) A is false, but R is true
  4. (d) A is true, but R is false
Answer & solution

Answer: (a) Both A and R are true, and R is the correct explanation of A

Correct Answer:
Option 1 – Both A and R are true, and R is the correct explanation of A
Explanation:
During exercise, muscles demand more oxygen and nutrients, causing the heart to beat faster (increased heart rate) and pump a greater volume of blood per minute (increased cardiac output). This increased cardiac output directly causes a temporary rise in blood pressure. Hence, both statements are true, and R correctly explains why A occurs.
Important Facts:
• Blood pressure returns to normal levels once exercise stops and the body recovers.
• Cardiac output = Heart rate × Stroke volume.
Correct Answer: Option 1 – Both A and R are true, and R is the correct explanation of A
RRB Group D 2025-26 – 18 August 2026 Shift 1 · Excretory system - kidney and nephron

Q19. What is the main purpose of making urine in animals?

  1. (a) Digest and absorb food
  2. (b) Store energy for future use
  3. (c) Produce hormones
  4. (d) Remove harmful metabolic wastes
Answer & solution

Answer: (d) Remove harmful metabolic wastes

Purpose of urine formation
Urine formation is the excretory function of the kidneys, by which nitrogenous and other harmful metabolic wastes (like urea, uric acid, excess salts and water) are filtered from the blood and removed from the body.
Correct Answer: Remove harmful metabolic wastes
RRB Group D 2025-26 – 18 August 2026 Shift 2 · Aerobic and anaerobic respiration

Q20. Which product is formed during anaerobic respiration in human muscles?

  1. (a) Water
  2. (b) Lactic acid
  3. (c) Carbon dioxide
  4. (d) Ethanol
Answer & solution

Answer: (b) Lactic acid

Anaerobic Respiration in Muscles
During vigorous exercise, when oxygen supply to muscles is insufficient, muscle cells undergo anaerobic respiration, breaking down glucose incompletely intolactic acid, causing muscle fatigue/cramps.
(This differs from anaerobic respiration in yeast, which produces ethanol and CO₂.)
Correct Answer: Lactic acid
RRB Group D 2025-26 – 18 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q21. Which of the following formations is the three carbon molecule formed during the breakdown of glucose?

  1. (a) Formation of fructose-6-phosphate
  2. (b) Formation of glucose-6-phosphate
  3. (c) Formation of pyruvate molecule
  4. (d) Formation of acetyl-co-A molecule
Answer & solution

Answer: (c) Formation of pyruvate molecule

Concept: Glycolysis (Breakdown of Glucose)
During cellular respiration, the first step (glycolysis) occurs in the cytoplasm, whereglucose (a 6-carbon molecule)is broken down intopyruvate (a 3-carbon molecule). This is a universal first step common to both aerobic and anaerobic respiration.
• Glucose-6-phosphate and fructose-6-phosphate — both 6-carbon intermediates formed early in glycolysis.
• Pyruvate — the 3-carbon end product of glycolysis.
• Acetyl-CoA — a 2-carbon molecule formed from pyruvate before entering the Krebs cycle.
Correct Answer: Formation of pyruvate molecule
RRB Group D 2025-26 – 17 August 2026 Shift 2 · Lymphatic system

Q22. In a scenario where excess extracellular fluid is not drained back into the blood, which system's malfunction is most likely responsible?

  1. (a) Lymphatic system
  2. (b) Circulatory system
  3. (c) Nervous system
  4. (d) Digestive system
Answer & solution

Answer: (a) Lymphatic system

Drainage of Extracellular Fluid
Thelymphatic systemcollects excess extracellular (interstitial) fluid that leaks out of blood capillaries and returns it to the bloodstream via lymph vessels and ducts. If this system malfunctions, fluid accumulates in tissues, causing swelling (oedema/lymphedema).
• The circulatory system moves blood but relies on the lymphatic system specifically to recover the fluid that escapes into tissue spaces.
• The nervous and digestive systems are unrelated to interstitial fluid drainage.
Correct Answer: Lymphatic system
RRB Group D 2025-26 – 17 August 2026 Shift 3 · Blood vessels, circulation and blood pressure

Q23. Which type of blood vessel is best suited for rapid exchange of gases and nutrients with body tissues?

  1. (a) Capillaries
  2. (b) Veins
  3. (c) Arteries
  4. (d) Lymph vessels
Answer & solution

Answer: (a) Capillaries

Blood Vessel for Exchange
Capillaries are the smallest blood vessels, with walls only one cell thick.
• This extremely thin wall allows rapid diffusion/exchange of gases (O₂, CO₂), nutrients, and waste products between blood and body tissues.
• Arteries and veins have thick, multi-layered walls not suited for direct exchange; lymph vessels carry lymph, not blood.
Correct Answer: Capillaries
RRB Group D 2025-26 – 14 August 2026 Shift 2 · Human respiratory system

Q24. Which of the following structures in throat is responsible for the prevention of collapse of air-passage in human beings?

  1. (a) Larynx
  2. (b) Rings of cartilage
  3. (c) Oesophagus
  4. (d) Pharynx
Answer & solution

Answer: (b) Rings of cartilage

Answer: Option 2 – Rings of cartilage.
•C-shaped cartilage ringskeep the trachea (air passage) from collapsing.
RRB Group D 2025-26 – 14 August 2026 Shift 2 · Blood vessels, circulation and blood pressure

Q25. To get quick action, a researcher must deliver a drug directly to the cells of an organ. To spread the drug best to the surrounding cells (for optimum diffusion of the drug), in which blood vessel should the drug be applied?

  1. (a) In the capillaries, because of their one-cell-thick walls
  2. (b) In the veins, because of the presence of valves
  3. (c) In the arteries, because of their thick elastic walls
  4. (d) In the veins, because they collect blood
Answer & solution

Answer: (a) In the capillaries, because of their one-cell-thick walls

Answer: Option 1 – In the capillaries, because of their one-cell-thick walls.
•Capillarieshave walls only one cell thick, allowing the best diffusion of the drug into surrounding cells.
RRB Group D 2025-26 – 14 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q26. In animal cells, the breakdown of pyruvate using oxygen during aerobic respiration occurs in the _______.

  1. (a) Mitochondria
  2. (b) Ribosome
  3. (c) Nucleus
  4. (d) Cytoplasm
Answer & solution

Answer: (a) Mitochondria

Answer: Option 1 – Mitochondria.
• Aerobic breakdown of pyruvate occurs in themitochondria.
RRB Group D 2025-26 – 13 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q27. Which product is commonly formed during anaerobic respiration in animals?

  1. (a) Glucose
  2. (b) Alcohol
  3. (c) Lactic acid
  4. (d) Oxygen
Answer & solution

Answer: (c) Lactic acid

Answer: Option 3 – Lactic acid.
• Anaerobic respiration in animal muscles produceslactic acid.
RRB Group D 2025-26 – 12 August 2026 Shift 1 · Blood vessels, circulation and blood pressure

Q28. A doctor observes a blood vessel with thick, elastic walls under a microscope. What is this vessel most likely to be?

  1. (a) A vein
  2. (b) An artery
  3. (c) A lymph vessel
  4. (d) A capillary
Answer & solution

Answer: (b) An artery

Answer: Option 2 – An artery.
•Arterieshave thick, elastic muscular walls to withstand high-pressure blood flow.
RRB Group D 2025-26 – 12 August 2026 Shift 2 · Human respiratory system

Q29. Which of the following does NOT occur during inhalation in human beings?

  1. (a) The diaphragm flattens downward
  2. (b) The chest cavity expands
  3. (c) Blood releases oxygen
  4. (d) Air enters the lungs
Answer & solution

Answer: (c) Blood releases oxygen

Answer: Option 3 – Blood releases oxygen.
• During inhalation, bloodtakes up (not releases) oxygen; the diaphragm flattens, chest expands, air enters.
RRB Group D 2025-26 – 12 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q30. During aerobic respiration in animals, the breakdown of a three-carbon pyruvate molecule produces carbon dioxide and _______.

  1. (a) Water
  2. (b) Glucose
  3. (c) Lactic acid
  4. (d) Ethanol
Answer & solution

Answer: (a) Water

Answer: Option 1 – Water.
• Aerobic respiration breaks pyruvate toCO₂ and water(with energy release).
RRB Group D 2025-26 – 11 August 2026 Shift 2 · Human respiratory system

Q31. What are the tiny balloon-like structures located at the end of the smallest tubes in the human lungs called?

  1. (a) Villi
  2. (b) Bronchi
  3. (c) Bronchioles
  4. (d) Alveoli
Answer & solution

Answer: (d) Alveoli

Answer: Option 4 – Alveoli.
• The tiny balloon-like sacs at the ends of bronchioles arealveoli, where gaseous exchange occurs.
RRB Group D 2025-26 – 10 August 2026 Shift 1 · Aerobic and anaerobic respiration

Q32. Which process in animals takes place in the absence of oxygen and releases a smaller amount of energy?

  1. (a) Transpiration
  2. (b) Anaerobic respiration
  3. (c) Aerobic respiration
  4. (d) Photosynthesis
Answer & solution

Answer: (b) Anaerobic respiration

Answer: Option 2 — Anaerobic respiration
Anaerobic respirationoccurs without oxygen and releases less energy → Option 2.
RRB Group D 2025-26 – 10 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q33. A patient with severe lung disease has reduced oxygen intake. Which cellular pathway is likely to be upregulated in their muscle cells during exertion, and what product accumulates as a result?

  1. (a) Direct conversion of glucose to ATP without any by-products
  2. (b) Anaerobic conversion of pyruvate to ethanol and carbon dioxide
  3. (c) Anaerobic conversion of pyruvate to lactic acid, leading to lactic acid accumulation
  4. (d) Aerobic breakdown of pyruvate to carbon dioxide and water
Answer & solution

Answer: (c) Anaerobic conversion of pyruvate to lactic acid, leading to lactic acid accumulation

Answer: Option 3 – Anaerobic conversion of pyruvate to lactic acid.
• With reduced oxygen, muscle cells respireanaerobically, converting pyruvate tolactic acid, which accumulates and causes muscle fatigue/cramps.
RRB Group D 2025-26 – 9 August 2026 Shift 1 · Heart - structure and functioning

Q34. What is the main purpose of having different chambers in the human heart?

  1. (a) To maintain the steady blood pressure throughout the systemic veins
  2. (b) To pump blood exclusively toward the lungs for gaseous exchange
  3. (c) To provide storage for excess blood during periods of rest
  4. (d) To prevent mixing of oxygen-rich and carbon dioxide-rich blood
Answer & solution

Answer: (d) To prevent mixing of oxygen-rich and carbon dioxide-rich blood

Answer: Option 4 — To prevent mixing of oxygen-rich and CO₂-rich blood
Separate heart chamberskeep oxygenated and deoxygenated blood from mixing→ Option 4.
RRB Group D 2025-26 – 9 August 2026 Shift 2 · Excretory system - kidney and nephron

Q35. What are the names of the closely spaced filtration units in each kidney?

  1. (a) Nephrons
  2. (b) Glomerulus
  3. (c) Neurons
  4. (d) Tubules
Answer & solution

Answer: (a) Nephrons

Answer: Option 1 — Nephrons
The kidney's filtration units arenephrons→ Option 1.
RRB Group D 2025-26 – 9 August 2026 Shift 3 · Human respiratory system

Q36. What happens when blood passes through the alveolar capillaries in the lungs?

  1. (a) Both gases remain unchanged in the circulating blood
  2. (b) Carbon dioxide enters blood and oxygen moves into alveoli
  3. (c) Oxygen enters blood and carbon dioxide moves into alveoli
  4. (d) Oxygen and carbon dioxide both enter the bloodstream from alveoli
Answer & solution

Answer: (c) Oxygen enters blood and carbon dioxide moves into alveoli

Answer: Option 3 — Oxygen enters blood and carbon dioxide moves into alveoli
In the lungs, O₂ diffuses into blood and CO₂ moves out into the alveoli → Option 3.
RRB Group D 2025-26 – 9 August 2026 Shift 3 · Excretory system - kidney and nephron

Q37. Which structure connects the kidneys to the urinary bladder?

  1. (a) Ureter
  2. (b) Bladder
  3. (c) Pelvis
  4. (d) Urethra
Answer & solution

Answer: (a) Ureter

Answer: Option 1 — Ureter
Theureterconnects each kidney to the urinary bladder → Option 1.
RRB Group D 2025-26 – 6 August 2026 Shift 1 · Blood vessels, circulation and blood pressure

Q38. Which statement CORRECTLY describes systolic and diastolic pressure in the human circulatory system?

  1. (a) Systole and diastole are both relaxations
  2. (b) Systole and diastole are both contractions
  3. (c) Systole is relaxation, diastole is contraction
  4. (d) Systole is contraction,diastole is relaxation
Answer & solution

Answer: (d) Systole is contraction,diastole is relaxation

Answer: Option 4 — Systole is contraction, diastole is relaxation
Systole = contraction,diastole = relaxationof the heart → Option 4.
RRB Group D 2025-26 – 6 August 2026 Shift 1 · Aerobic and anaerobic respiration

Q39. What is the process in which organisms take in oxygen and use it to break down food for cellular activities called?

  1. (a) Photosynthesis
  2. (b) Transpiration
  3. (c) Fermentation
  4. (d) Respiration
Answer & solution

Answer: (d) Respiration

Answer: Option 4 — Respiration
Taking in oxygen to break down food for energy isrespiration→ Option 4.
RRB Group D 2025-26 – 6 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q40. Which of the following facts about cellular respiration is INCORRECT?

  1. (a) The first step of glucose breakdown takes place in the cytoplasm.
  2. (b) Anaerobic respiration occurs in the absence of oxygen.
  3. (c) Anaerobic respiration in yeast produces ethanol and carbon dioxide.
  4. (d) Anaerobic respiration in yeast produces water as a major end product.
Answer & solution

Answer: (d) Anaerobic respiration in yeast produces water as a major end product.

Answer: Option 4 — Anaerobic respiration in yeast produces water as a major end product
This is INCORRECT — yeast's anaerobic respiration producesethanol and CO₂, not water → Option 4.
RRB Group D 2025-26 – 5 August 2026 Shift 2 · Heart - structure and functioning

Q41. Which chamber of the human heart pumps blood directly to the lungs for oxygenation?

  1. (a) Left ventricle
  2. (b) Left atrium
  3. (c) Right atrium
  4. (d) Right ventricle
Answer & solution

Answer: (d) Right ventricle

Answer: Option 4 — Right ventricle
Theright ventriclepumps deoxygenated blood to the lungs → Option 4.
RRB Group D 2025-26 – 5 August 2026 Shift 3 · Lymphatic system

Q42. A patient has difficulty transporting absorbed fats from the intestine. Which fluid's impaired function could cause this problem?

  1. (a) Lymph
  2. (b) Plasma
  3. (c) Blood cells
  4. (d) Platelets
Answer & solution

Answer: (a) Lymph

Answer: Option 1 — Lymph
Lymphtransports absorbed fats (chylomicrons) from the intestine → Option 1.
RRB Group D 2025-26 – 4 August 2026 Shift 1 · Heart - structure and functioning

Q43. Which structure prevents the backward flow of blood during contractions of the heart?

  1. (a) Arteries
  2. (b) Muscles
  3. (c) Septa
  4. (d) Valves
Answer & solution

Answer: (d) Valves

Answer: Option 4 — Valves
Heartvalvesprevent the backward flow of blood during contraction → Option 4.
RRB Group D 2025-26 – 4 August 2026 Shift 2 · Aerobic and anaerobic respiration

Q44. In animals, anaerobic respiration primarily results in the formation of _____.

  1. (a) Lactic acid
  2. (b) Carbon dioxide
  3. (c) Glucose
  4. (d) Water
Answer & solution

Answer: (a) Lactic acid

Answer: Option 1 — Lactic acid
In animals (muscles), anaerobic respiration produceslactic acid→ Option 1.
RRB Group D 2025-26 – 4 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q45. Which gas is essential for aerobic respiration in animals?

  1. (a) Nitrogen
  2. (b) Hydrogen
  3. (c) Carbon dioxide
  4. (d) Oxygen
Answer & solution

Answer: (d) Oxygen

Answer: Option 4 — Oxygen
Aerobic respiration requiresoxygen→ Option 4.
RRB Group D 2025-26 – 4 August 2026 Shift 3 · Blood vessels, circulation and blood pressure

Q46. Match 'Column A' with 'Column B' in context of the muscular layers in blood vessels.
[TABLE]
| Column A | | Column B
(a) | Thick tunica media | (i) | Vein
(b) | Smallest vessel diameter | (ii) | Artery
(c) | Large lumen | (iii) | Capillary
(d) | Endothelium | (iv) | All blood vessels
[/TABLE]

  1. (a) a–i, b–ii, c–iv, d–iii
  2. (b) a–ii, b–iv, c–i, d–iii
  3. (c) a–ii, b–iii, c–i, d–iv
  4. (d) a–iii, b–ii, c–i, d–iv
Answer & solution

Answer: (c) a–ii, b–iii, c–i, d–iv

Answer: Option 3 — a–ii, b–iii, c–i, d–iv
Matching the blood-vessel muscular-layer descriptions givesa–ii, b–iii, c–i, d–iv→ Option 3. (Answer per the official key/table given in the paper.)
RRB Group D 2025-26 – 4 August 2026 Shift 3 · Blood - components and functions

Q47. In human beings, the respiratory pigment that carries oxygen is ______.

  1. (a) haemoglobin
  2. (b) myosin
  3. (c) chlorophyll
  4. (d) insulin
Answer & solution

Answer: (a) haemoglobin

Answer: Option 1 — Haemoglobin
Haemoglobinis the respiratory pigment that carries oxygen → Option 1.
RRB Group D 2025-26 – 3 August 2026 Shift 1 · Aerobic and anaerobic respiration

Q48. The process in plants that involves the breakdown of glucose to release energy is called:

  1. (a) Excretion
  2. (b) Transpiration
  3. (c) Respiration
  4. (d) Photosynthesis
Answer & solution

Answer: (c) Respiration

Answer: Option 3 — Respiration
Concept: Respirationis the process that breaks down glucose to release energy (ATP) in cells. (Photosynthesis makes glucose; transpiration is water loss; excretion removes waste.) → Option 3.
RRB Group D 2025-26 – 3 August 2026 Shift 2 · Heart - structure and functioning

Q49. Why do the ventricles of the heart have thicker muscular walls compared to the atria?

  1. (a) They separate oxygenated and de-oxygenated blood
  2. (b) They store more blood before each contraction
  3. (c) They require more nerves for neural control
  4. (d) They pump blood to organs throughout the body
Answer & solution

Answer: (d) They pump blood to organs throughout the body

Answer: Option 4 — They pump blood to organs throughout the body
Ventricles pump blood out of the heartagainst high resistance(to the whole body/lungs), needing greater force, so they havethicker muscular wallsthan the atria (which only push blood to the ventricles) → Option 4.
RRB Group D 2025-26 – 3 August 2026 Shift 3 · Aerobic and anaerobic respiration

Q50. Which molecule is immediately synthesized using energy released during cellular respiration in animal cells?

  1. (a) Guanosine Diphosphate (GDP)
  2. (b) Nicotinamide adenine Dinucleotide (NAD)
  3. (c) Adenosine Diphosphate (ADP)
  4. (d) Adenosine triphosphate (ATP)
Answer & solution

Answer: (d) Adenosine triphosphate (ATP)

Answer: Option 4 — ATP (Adenosine triphosphate)
The energy released in cellular respiration is stored immediately inATP→ Option 4.
SSC GD 2026 – 30 May 2026 Shift 3 · Aerobic and anaerobic respiration

Q51. In cells, the molecule that functions as the main energy currency is abbreviated as ATP. What is the full form of ATP?

  1. (a) Adenosine triphosphate
  2. (b) Adenine thymine phosphate
  3. (c) Adenosine tetraphosphate
  4. (d) Adenine triphosphate
Answer & solution

Answer: (a) Adenosine triphosphate

Correct Answer: Adenosine triphosphate (Option 1)
ATP stands for Adenosine Triphosphate. It is the primary energy currency of all living cells, produced mainly through cellular respiration (in the mitochondria). ATP releases energy when one of its three phosphate groups is removed ( hydrolysed ), converting it to ADP (Adenosine Diphosphate). This energy powers virtually all cellular activities.
Why others are wrong:
- Adenine thymine phosphate: ATP does not involve thymine; this is not a real molecule in this context.
- Adenosine tetraphosphate: ATP has three (tri) phosphate groups, not four (tetra).
- Adenine triphosphate: The nucleoside component is Adenosine (adenine + ribose sugar), not just Adenine.
SSC GD 2026 – 30 May 2026 Shift 1 · Aerobic and anaerobic respiration

Q52. Which of the following pairs is correct regarding respiration?
I. Anaerobic — Presence of oxygen
II. Aerobic — Absence of oxygen

  1. (a) Only I
  2. (b) Only II
  3. (c) Both I and II
  4. (d) Neither I nor II
Answer & solution

Answer: (d) Neither I nor II

Correct Answer: Neither I nor II — Option (d)
Both statements are INCORRECT — the definitions of anaerobic and aerobic respiration are swapped in both statements. About Respiration types: Aerobic Respiration: Definition: Respiration that occurs IN THE PRESENCE OF OXYGEN; Products: CO₂ + H₂O + Energy (ATP); Location: Mitochondria; More efficient — produces 36-38 ATP per glucose molecule; Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP; Examples: Most cells in our body use aerobic respiration; Anaerobic Respiration: Definition: Respiration that occurs IN THE ABSENCE OF OXYGEN; Products vary by organism: In muscles (during intense exercise): Lactic acid + Energy (small amount); In yeast/microbes: Ethanol + CO₂ + Energy (small amount); Less efficient — produces only 2 ATP per glucose molecule; Equation (in muscles): C₆H₁₂O₆ → 2C₃H₆O₃ (lactic acid) + 2 ATP; Examples: Yeast (fermentation), some bacteria, muscle cells during strenuous exercise; Evaluation of statements: Statement I — 'Anaerobic — Presence of oxygen' — WRONG: Anaerobic means WITHOUT oxygen (prefix 'an' = without); anaerobic respiration occurs in the ABSENCE of oxygen; Statement II — 'Aerobic — Absence of oxygen' — WRONG: Aerobic means WITH oxygen (prefix 'aero' = air/oxygen); aerobic respiration requires the PRESENCE of oxygen; Both statements have the oxygen conditions REVERSED; Therefore, NEITHER I NOR II is correct; Key memory tip: 'Aerobic' = 'Aero' = Air = With oxygen; 'Anaerobic' = 'Ana' = Against/Without = Without oxygen.
Option (a) Only I — Incorrect: Statement I is INCORRECT — 'Anaerobic — Presence of oxygen' is WRONG; anaerobic respiration occurs in the ABSENCE of oxygen (prefix 'an' = without); in fact, ' an ' before 'aerobic' means 'without air/oxygen'; both statements are wrong, so 'Only I' cannot be the answer.
Option (b) Only II — Incorrect: Statement II is INCORRECT — 'Aerobic — Absence of oxygen' is WRONG; aerobic respiration requires the PRESENCE of oxygen (prefix 'aero' = air = oxygen); aerobic respiration uses oxygen to completely oxidize glucose into CO₂ and water; both statements have the oxygen conditions reversed, so 'Only II' cannot be the answer.
Option (c) Both I and II — Incorrect: BOTH statements are incorrect; Statement I wrongly says anaerobic occurs in presence of oxygen (it occurs in ABSENCE); Statement II wrongly says aerobic occurs in absence of oxygen (it occurs in PRESENCE); both definitions are exactly reversed; the correct pairing is: Aerobic = presence of oxygen; Anaerobic = absence of oxygen.
SSC GD 2026 – 25 May 2026 Shift 1 · Excretory system - kidney and nephron

Q53. In relation to excretion in humans, which of the following statements is correct?
I. Kidneys are located on both sides of the backbone
in the abdomen.
II. Urine produced in the kidneys passes through the
ureter to the urinary bladder.

  1. (a) Only I
  2. (b) Only II
  3. (c) Both I and II
  4. (d) Neither I nor II
Answer & solution

Answer: (c) Both I and II

Correct Answer: Both I and II — Option (c)
Both statements about human excretion are correct. Statement I Analysis — 'Kidneys are located on both sides of the backbone in the abdomen' (CORRECT): Humans have two kidneys (bean-shaped organs); They are located in the abdominal cavity on either side of the vertebral column (backbone/spine); Position: Retroperitoneal position (behind the peritoneum) on the posterior wall of the abdomen; The right kidney is slightly lower than the left (due to the liver); Each kidney is approximately 10-12 cm long, 5-6 cm wide, and 3-4 cm thick; Statement II Analysis — 'Urine produced in the kidneys passes through the ureter to the urinary bladder' (CORRECT): The urinary system flow: Kidneys (produce urine) → Ureter (tube from each kidney to bladder) → Urinary Bladder (storage) → Urethra (discharge from body); Each kidney has one ureter (tube) — so two ureters total; Ureters are muscular tubes (25-30 cm long) that carry urine from kidneys to the urinary bladder through peristaltic movements; About kidney function: Main excretory organ in humans; Filters blood to remove waste products (urea, creatinine, excess salts, water); Maintains blood pH and osmotic balance; Produces urine containing urea (main nitrogenous waste), uric acid, and excess minerals.
Option (a) Only I — Incorrect: Both Statement I (kidneys on both sides of backbone) and Statement II (urine passes through ureter to bladder) are anatomically correct; selecting 'Only I' ignores that Statement II is also correct.
Option (b) Only II — Incorrect: Both statements are correct; Statement I accurately describes the location of kidneys, and Statement II correctly describes urine flow through the ureter; 'Only II' is incomplete.
Option (d) Neither I nor II — Incorrect: Both statements are factually accurate about human excretion; 'Neither I nor II' is completely incorrect.
SSC GD 2026 – 21 May 2026 Shift 1 · Excretory system - kidney and nephron

Q54. The main nitrogenous waste products excreted by the human kidney are _____.

  1. (a) Carbon dioxide and Oxygen
  2. (b) Urea and Uric acid
  3. (c) Amino acids and Glucose
  4. (d) Fatty acids and Glycerol
Answer & solution

Answer: (b) Urea and Uric acid

Correct Answer: Urea and Uric acid — Option (b)
The main nitrogenous waste products excreted by the human kidney are urea and uric acid. Urea: The primary nitrogenous waste in humans; produced in the liver through the urea cycle (ornithine cycle) from the breakdown of amino acids (deamination); urea is filtered from the blood by the kidneys and excreted in urine; approximately 25-30 grams of urea is excreted daily; Uric acid: Produced from the breakdown of purine nucleotides (adenine and guanine from DNA/RNA); also filtered and excreted by the kidneys; elevated uric acid levels cause gout (a painful joint condition due to uric acid crystal deposition); Other nitrogenous compounds in urine: Creatinine (from muscle metabolism), ammonia (very small amounts — toxic), urea (majority — about 80-90% of total nitrogen excretion); Types of excretion based on waste product: Ammonotelic (ammonia — aquatic animals like fish), Ureotelic (urea — mammals including humans, amphibians), Uricotelic (uric acid — birds, reptiles, insects — conserve water). Humans are primarily UREOTELIC but also excrete uric acid.
Option (a) Carbon dioxide and Oxygen — Incorrect: Carbon dioxide is a waste product of cellular respiration but is eliminated through the lungs (respiratory system), NOT the kidneys; oxygen is not a waste product — it is essential for life; the main nitrogenous wastes excreted by the kidney are urea and uric acid.
Option (c) Amino acids and Glucose — Incorrect: Amino acids and glucose are valuable nutrients that are normally reabsorbed back into the blood by the kidney tubules; they appear in urine only in disease conditions (like diabetes mellitus for glucose); they are NOT the main nitrogenous waste products excreted by the kidneys.
Option (d) Fatty acids and Glycerol — Incorrect: Fatty acids and glycerol are products of fat digestion and are metabolized for energy; they are not nitrogenous compounds and are NOT excreted as waste by the kidneys; the main nitrogenous wastes are urea and uric acid.
SSC GD 2026 – 8 May 2026 Shift 3 · Aerobic and anaerobic respiration

Q55. In the aerobic breakdown of pyruvate (in mitochondria), which of the following is produced?

  1. (a) Lactic acid + energy
  2. (b) Carbon dioxide + water + energy
  3. (c) Ethanol + carbon dioxide + energy
  4. (d) Lactic acid + energy + carbon dioxide
Answer & solution

Answer: (b) Carbon dioxide + water + energy

Correct Answer: Carbon dioxide + water + energy — Option (b)
In aerobic respiration, pyruvate (produced from glucose during glycolysis in the cytoplasm) is transported into the mitochondria, where it undergoes aerobic breakdown (oxidative decarboxylation → Krebs cycle → Electron Transport Chain). The complete aerobic oxidation of pyruvate produces: Carbon dioxide (CO₂) — released as a waste gas; Water (H₂O) — produced when hydrogen combines with oxygen; Energy (ATP) — approximately 36–38 ATP molecules per glucose. The overall reaction: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP).
Option (a) Lactic acid + energy — Incorrect: Lactic acid is produced during ANAEROBIC respiration in muscle cells (when oxygen is insufficient), not aerobic breakdown in mitochondria.
Option (c) Ethanol + carbon dioxide + energy — Incorrect: Ethanol and CO₂ are produced during anaerobic fermentation by yeast (alcoholic fermentation), not aerobic mitochondrial breakdown.
Option (d) Lactic acid + energy + carbon dioxide — Incorrect: This is a mix of anaerobic (lactic acid) and aerobic (CO₂) products; complete aerobic breakdown produces CO₂, H₂O, and energy — not lactic acid.
RRB NTPC GL CBT-1 2025-26 – 24 March 2026 Shift 2 · Excretory system - kidney and nephron

Q56. When the kidneys are not able to reabsorb the glucose, then the glucose will be excreted through the urine. This condition is known as:

  1. (a) Lupus nephritis
  2. (b) Cystinosis
  3. (c) Ascites
  4. (d) Glycosuria
Answer & solution

Answer: (d) Glycosuria

Topic:Renal Physiology - Glucose Excretion
Normal kidney function:Reabsorbs all filtered glucose in proximal tubule.
When reabsorption fails:Glucose appears in urine.
Glycosuria:Presence of glucose in urine due to:
• Diabetes mellitus (high blood glucose)
• Renal threshold exceeded
• Kidney tubule dysfunction
Other options:
• Lupus nephritis: Autoimmune kidney inflammation
• Cystinosis: Cystine crystal accumulation
Answer: Option 4 → Glycosuria
RRB Technician Grade III 2025-26 – 10 March 2026 Shift 2 · Aerobic and anaerobic respiration

Q57. Which of the following best explains why anaerobic respiration releases less energy than aerobic respiration?

  1. (a) It does not require enzymes.
  2. (b) It uses less glucose.
  3. (c) It partially breaks down glucose.
  4. (d) It occurs slower than aerobic respiration.
Answer & solution

Answer: (c) It partially breaks down glucose.

Anaerobic respiration releases less energy because it does not completely break down glucose.
In anaerobic respiration, glucose is only partially broken down into products like lactic acid or ethanol and carbon dioxide.
In contrast, aerobic respiration fully breaks down glucose into carbon dioxide and water, releasing more energy.
Partial breakdown means less energy is extracted from each glucose molecule, resulting in lower energy yield.
RRB Technician Grade III 2025-26 – 10 March 2026 Shift 3 · Blood vessels, circulation and blood pressure

Q58. Which of the following correctly explains why veins have valves but arteries do not?

  1. (a) Veins carry blood under high pressure, so valves prevent it from bursting
  2. (b) Arteries carry oxygenated blood and do not need valves
  3. (c) Veins carry blood at low pressure and need valves to prevent backflow
  4. (d) Arteries are located deep inside the body and are supported by muscles
Answer & solution

Answer: (c) Veins carry blood at low pressure and need valves to prevent backflow

Veins carry blood at low pressure.
Because of low pressure, blood flow can reverse direction in veins.
Valves in veins prevent this backflow and ensure one-way blood flow to the heart.
Arteries carry blood under high pressure, so they do not require valves.
Hence, veins have valves but arteries do not.
RRB Technician Grade III 2025-26 – 9 March 2026 Shift 2 · Blood vessels, circulation and blood pressure

Q59. Blood pressure is recorded as two values: _________ pressure, measured when the heart contracts, and ___________ pressure, measured when the heart relaxes.

  1. (a) Diastolic; Venous
  2. (b) Maximum; Systolic
  3. (c) Systolic; Diastolic
  4. (d) Diastolic; Systolic
Answer & solution

Answer: (c) Systolic; Diastolic

Blood pressure is recorded as two values:
Systolic pressure, measured when the heart contracts,
and Diastolic pressure, measured when the heart relaxes.
Therefore, the correct pair is Systolic and Diastolic pressure.
RRB Technician Grade III 2025-26 – 9 March 2026 Shift 1 · Heart - structure and functioning

Q60. Which of the following statements correctly describes the transportation of blood from the heart to the lungs?

  1. (a) Deoxygenated blood is pumped from the right ventricle to the lungs.
  2. (b) Deoxygenated blood is pumped from the left ventricle to the lungs.
  3. (c) Oxygenated blood is carried from the lungs to the right atrium.
  4. (d) Oxygenated blood flows from the left ventricle to the lungs for purification.
Answer & solution

Answer: (a) Deoxygenated blood is pumped from the right ventricle to the lungs.

The right ventricle pumps deoxygenated blood towards the lungs for oxygenation.
Blood travels from the right ventricle through the pulmonary artery to lungs.
The left ventricle pumps oxygenated blood to the body, not the lungs.
Therefore, only option 1 correctly describes blood flow from heart to lungs.
RRB Technician Grade III 2025-26 – 6 March 2026 Shift 1 · Excretory system - kidney and nephron

Q61. The urine formed in the kidneys passes through the ______ into the _____ where it is stored until excreted.

  1. (a) urinary bladder; urethra
  2. (b) ureters; urinary bladder
  3. (c) nephrons; urethra
  4. (d) urethra; ureters
Answer & solution

Answer: (b) ureters; urinary bladder

The urine is formed in the kidneys.
It passes through the ureters into the urinary bladder.
The urinary bladder stores the urine until it is excreted.
Hence, the correct sequence is: kidneys → ureters → urinary bladder → urethra.
Option 2 states ureters and urinary bladder, which is correct.
Final answer: Option 2
RRB Technician Grade III 2025-26 – 6 March 2026 Shift 3 · Lymphatic system

Q62. Which of the following components is absent in lymph but present in blood?

  1. (a) Plasma
  2. (b) White blood cells (WBCs)
  3. (c) Water
  4. (d) Platelets
Answer & solution

Answer: (d) Platelets

The component present in blood but absent in lymph is platelets.
Lymph contains plasma, water, and white blood cells (mainly lymphocytes).
However, platelets are generally absent in lymph as they remain within the blood vessels and do not circulate in lymphatic fluid.
Hence, the correct answer is platelets.
RRB Technician Grade III 2025-26 – 6 March 2026 Shift 2 · Dialysis and other excretory organs

Q63. Which of the following statements correctly explains the working principle of dialysis in an artificial kidney?

  1. (a) Dialysis removes wastes from blood by diffusion across a semi-permeable membrane.
  2. (b) Dialysis reabsorbs essential nutrients and salts like a normal kidney.
  3. (c) Dialysis removes nitrogenous wastes from blood through active transport.
  4. (d) Dialysis uses high pressure to force wastes out of the blood into the dialysing fluid.
Answer & solution

Answer: (a) Dialysis removes wastes from blood by diffusion across a semi-permeable membrane.

Option 1 is correct.
Dialysis works by removing wastes and excess substances from blood by diffusion.
A semi-permeable membrane allows diffusion of small waste molecules from blood into the dialysis fluid.
Essential nutrients are retained in the blood as they are larger molecules or selectively reabsorbed in the body, not during dialysis.
Other options are incorrect because dialysis does not involve active transport or high pressure.
Hence, dialysis mimics kidney function by diffusion across a semi-permeable membrane.
Final answer: Option 1
RRB JE CBT-1 2025-26 – 25 February 2026 Shift 3 · Excretory system - kidney and nephron

Q64. Which waste based difference between the renal artery and renal vein is directly related to excretory function?

  1. (a) The renal vein has higher pressure
  2. (b) The renal artery has more valves
  3. (c) The renal artery contains more urea
  4. (d) The renal vein contains more oxygen
Answer & solution

Answer: (c) The renal artery contains more urea

Solution:
Therenal arterybrings blood to the kidneys containingmore urea (waste).
Kidneysfilter and remove ureaduring excretion.
Hence, blood in therenal vein has less ureaafter filtration.
RRB JE CBT-1 2025-26 – 20 February 2026 Shift 3 · Respiration and excretion in other organisms

Q65. A gardener notices fallen leaves under a tree. Which strategy of plant excretion does this illustrate, and what type of waste handling is involved?

  1. (a) Converting waste into fruits.
  2. (b) Excreting waste through roots only.
  3. (c) Storing waste in leaves that fall off.
  4. (d) Releasing waste as oxygen only.
Answer & solution

Answer: (c) Storing waste in leaves that fall off.

Correct option is 3.
Plants produce waste materials like phenols and tannins.
These wastes are stored in leaves or other parts.
When leaves fall off, they remove stored waste from the plant body.
This natural disposal method is a plant excretion strategy.
Hence, fallen leaves under the tree show storage of waste in leaves that fall off.
Final answer: Option 3
RRB JE CBT-1 2025-26 – 20 February 2026 Shift 2 · Blood - components and functions

Q66. A low platelet count may lead to __________.

  1. (a) Fever
  2. (b) Infection
  3. (c) Anemia
  4. (d) Excessive bleeding
Answer & solution

Answer: (d) Excessive bleeding

A low platelet count reduces blood clotting ability.
Platelets help in forming clots to stop bleeding.
When platelet count is low, bleeding may continue excessively.
Therefore, low platelet count leads to excessive bleeding.
Final answer: Option 4
RRB JE CBT-1 2025-26 – 20 February 2026 Shift 1 · Respiration and excretion in other organisms

Q67. A plant sheds its leaves and bark to remove stored waste products. How does this strategy differ from the way animals excrete wastes?

  1. (a) Plants use parts that will be shed, while animals have specialized organs for excretion.
  2. (b) Plants use blood circulation for excretion, unlike animals.
  3. (c) Plants use digestive systems to remove waste, unlike animals.
  4. (d) Plants have a single organ system for waste removal, unlike animals.
Answer & solution

Answer: (a) Plants use parts that will be shed, while animals have specialized organs for excretion.

Option 1 is correct.
Plants remove waste by shedding parts like leaves and bark which contain stored waste.
Animals have specialised organs such as kidneys and liver for excretion.
This fundamental difference lies in structural adaptations for waste removal.
Thus, plants lose parts that serve multiple functions while animals use specific organs solely for excretion.
This makes option 1 the accurate description of the difference.
Final answer: Option 1
RRB JE CBT-1 2025-26 – 20 February 2026 Shift 3 · Heart - structure and functioning

Q68. If the bicuspid (mitral) valve fails to close properly, which immediate effect is most likely during ventricular contraction?

  1. (a) Backflow of blood from the right ventricle to the right atrium
  2. (b) Mixing of oxygenated and deoxygenated blood in the ventricles
  3. (c) Backflow of blood from the left ventricle to the left atrium
  4. (d) Reduced flow of blood to the lungs
Answer & solution

Answer: (c) Backflow of blood from the left ventricle to the left atrium

The bicuspid (mitral) valve is located between the left atrium and left ventricle.
Its function is to prevent blood from flowing backward into the atrium when the ventricle contracts.
If it fails to close properly, blood will flow back from the left ventricle to the left atrium during ventricular contraction.
This condition is called mitral regurgitation and causes inefficiency in the heart's pumping action.
Final answer: Option 3
RRB JE CBT-1 2025-26 – 20 February 2026 Shift 2 · Excretory system - kidney and nephron

Q69. Which statement best explains why blood cells are NOT found in the urine of a healthy person?

  1. (a) They are filtered and returned to the blood
  2. (b) They are broken down in the kidneys
  3. (c) They are reabsorbed in tubules
  4. (d) They are too large to pass through glomerular pores
Answer & solution

Answer: (d) They are too large to pass through glomerular pores

The glomerulus in kidneys filters the blood.
Only smaller molecules and water pass through the glomerular pores.
Blood cells are large in size and cannot pass through these pores.
Hence, blood cells do not appear in the urine of a healthy person.
Final answer: Option 4
SSC MTS 2025 – 19 February 2026 Shift 2 · Aerobic and anaerobic respiration

Q70. What is the first step in the break-down of glucose in all organisms?

  1. (a) Conversion of glucose into carbon dioxide and water
  2. (b) Conversion of pyruvate into ethanol
  3. (c) Break-down of glucose into pyruvate
  4. (d) Conversion of pyruvate into lactic acid
Answer & solution

Answer: (c) Break-down of glucose into pyruvate

The correct answer is option 3.
In all living organisms, the first step in glucose breakdown (cellular respiration) is glycolysis — the breakdown of one glucose molecule (6 carbons) into two molecules of pyruvate (3 carbons each). Glycolysis occurs in the cytoplasm and does not require oxygen, making it common to both aerobic and anaerobic respiration.
Option 1 is incorrect: Conversion of glucose into CO₂ and water is the end result of complete aerobic respiration, not the first step.
Option 2 is incorrect: Conversion of pyruvate into ethanol (alcoholic fermentation) occurs in some organisms like yeast as a later step, after glycolysis.
Option 4 is incorrect: Conversion of pyruvate into lactic acid (lactic acid fermentation) occurs in muscle cells under anaerobic conditions, as a later step after glycolysis.
SSC MTS 2025 – 19 February 2026 Shift 3 · Excretory system - kidney and nephron

Q71. Which biological process is involved in the removal of harmful metabolic wastes from the body?

  1. (a) Digestion
  2. (b) Metabolism
  3. (c) Respiration
  4. (d) Excretion
Answer & solution

Answer: (d) Excretion

Correct Answer: Excretion (Option 4)
Excretion is the biological process by which metabolic waste products (such as urea, uric acid, CO₂, excess water and salts) are removed from the body. Organs involved include the kidneys (urine), lungs (CO₂), and skin (sweat).
Why other options are wrong:
Option 1 – Digestion is the breakdown of food into absorbable nutrients.
Option 2 – Metabolism refers to all chemical reactions occurring in the body (anabolism + catabolism).
Option 3 – Respiration is the process of energy production from glucose using oxygen.
RRB JE CBT-1 2025-26 – 19 February 2026 Shift 1 · Excretory system - kidney and nephron

Q72. Refer to the two statements given below and choose the CORRECT option.Statement A: Selective reabsorption in nephrons helps maintain water and salt balance in the body.Statement B: Selective reabsorption prevents nitrogenous wastes from entering the filtrate.

  1. (a) Statement A is correct but B is incorrect.
  2. (b) Both statements A and B are incorrect.
  3. (c) Both statements A and B are correct.
  4. (d) Statement A is incorrect but B is correct.
Answer & solution

Answer: (a) Statement A is correct but B is incorrect.

Statement A is correct: Selective reabsorption in nephrons helps the body maintain water and salt balance by reabsorbing useful substances back into the blood.
Statement B is incorrect: Selective reabsorption does not prevent nitrogenous wastes from entering the filtrate; instead, nitrogenous wastes remain in the filtrate to be excreted as urine.
Therefore, only Statement A is correct and Statement B is incorrect.
Final answer: Option 1
RRB JE CBT-1 2025-26 – 19 February 2026 Shift 3 · Aerobic and anaerobic respiration

Q73. During aerobic respiration, each pyruvate molecule is broken down to give ______ molecules of carbon dioxide.

  1. (a) Four
  2. (b) One
  3. (c) Three
  4. (d) Two
Answer & solution

Answer: (c) Three

During aerobic respiration, each pyruvate molecule enters the mitochondria. It is further broken down in the Krebs cycle (Citric Acid cycle). In this process, one pyruvate molecule produces three molecules of carbon dioxide. Hence, 3 molecules of CO2 are produced from each pyruvate.
RRB JE CBT-1 2025-26 – 19 February 2026 Shift 1 · Blood vessels, circulation and blood pressure

Q74. Systolic pressure is measured when the heart __________.

  1. (a) Contracts
  2. (b) Stops beating
  3. (c) Fills with blood
  4. (d) Relaxes
Answer & solution

Answer: (a) Contracts

Systolic pressure is the pressure exerted on the arteries when the heart contracts.
During this phase, the heart pumps blood into the arteries, increasing the pressure.
Hence, systolic pressure is measured when the heart contracts.
Option 1 is correct.
This completes the answer.
RRB JE CBT-1 2025-26 – 19 February 2026 Shift 2 · Heart - structure and functioning

Q75. Which observation best supports the statement that humans have double circulation of blood?

  1. (a) Oxygenated and deoxygenated blood mix in the heart
  2. (b) Blood flows only once through the heart in one complete cycle
  3. (c) Blood passes through the heart twice in one complete circulation
  4. (d) Right side of the heart pumps oxygenated blood
Answer & solution

Answer: (c) Blood passes through the heart twice in one complete circulation

Double circulation means blood passes through the heart two times in one complete cycle.
This separates oxygenated and deoxygenated blood, ensuring efficient oxygen transport.
Option 3 states 'Blood passes through the heart twice in one complete circulation', which exactly describes double circulation.
Therefore, option 3 best supports the statement about human double circulation of blood.
Hence, the correct answer is Option 3.
RRB JE CBT-1 2025-26 – 19 February 2026 Shift 2 · Excretory system - kidney and nephron

Q76. Which process is responsible for the removal of waste byproducts from the body in living organisms?

  1. (a) Excretion
  2. (b) Nutrition
  3. (c) Transportation
  4. (d) Respiration
Answer & solution

Answer: (a) Excretion

The process that removes waste byproducts from the body is called excretion.
Excretion eliminates harmful substances like urea, carbon dioxide, and excess salts.
This process helps maintain internal chemical balance and homeostasis in living organisms.
Nutrition is related to intake and utilisation of food, not waste removal.
Transportation involves movement of substances internally, not elimination.
Respiration is the process of producing energy by exchanging gases, not directly responsible for waste removal.
Hence, the correct answer is Excretion.
RRB JE CBT-1 2025-26 – 19 February 2026 Shift 3 · Aerobic and anaerobic respiration

Q77. Why do muscle cells sometimes respire anaerobically during heavy exercise?

  1. (a) Because the supply of oxygen is limited
  2. (b) Because the body wants to store energy
  3. (c) Because lactic acid is required
  4. (d) Because glucose is unavailable
Answer & solution

Answer: (a) Because the supply of oxygen is limited

During heavy exercise, muscle cells require more energy rapidly.
Oxygen supply becomes limited as breathing and blood flow can't keep up.
Muscle cells start anaerobic respiration to produce energy without oxygen.
This allows continued ATP production but results in lactic acid formation.
Hence, anaerobic respiration happens because oxygen supply is limited.
Final answer: Option 1
SSC MTS 2025 – 18 February 2026 Shift 3 · Aerobic and anaerobic respiration

Q78. Breakdown of pyruvate using oxygen takes place in the _____ in a cell.

  1. (a) cytoplasm
  2. (b) lysosome
  3. (c) mitochondria
  4. (d) cell membrane
Answer & solution

Answer: (c) mitochondria

The correct answer is option 3.
After glycolysis (which occurs in the cytoplasm and produces pyruvate), the pyruvate is transported into the mitochondria. Here, in the presence of oxygen, it undergoes aerobic respiration — it is completely broken down into carbon dioxide and water, releasing a large amount of energy (ATP). This is why mitochondria are called the 'powerhouse of the cell'.
Option 1 is incorrect: The cytoplasm is the site of glycolysis (breakdown of glucose to pyruvate), not the aerobic breakdown of pyruvate.
Option 2 is incorrect: Lysosomes are the digestive organelles of the cell responsible for breaking down waste and foreign material, not for aerobic respiration.
Option 4 is incorrect: The cell membrane controls passage of substances in and out of the cell; it is not involved in energy production.
SSC MTS 2025 – 17 February 2026 Shift 1 · Blood vessels, circulation and blood pressure

Q79. How do veins ensure that blood flows in one direction in human body?

  1. (a) By having thick, elastic walls
  2. (b) By having a low blood pressure
  3. (c) By contracting and relaxing
  4. (d) By using valves
Answer & solution

Answer: (d) By using valves

Veins ensure unidirectional blood flow by using valves. These pocket-like flaps open to allow blood to flow toward the heart and close to prevent backflow. Thick elastic walls are a feature of arteries, not veins. Low blood pressure and contracting/relaxing are not the mechanisms by which veins direct blood flow.
SSC MTS 2025 – 17 February 2026 Shift 2 · Heart - structure and functioning

Q80. The dividing wall of the heart which differentiates the heart into left and right side is called _____.

  1. (a) Aorta
  2. (b) Septum
  3. (c) Vena cava
  4. (d) SA node
Answer & solution

Answer: (b) Septum

The Septum is the muscular wall that divides the heart into its left and right sides. The interventricular septum separates the left and right ventricles. Aorta is the main artery carrying blood from the heart; Vena cava is the large vein returning blood to the heart; SA node is the heart's natural pacemaker.
SSC MTS 2025 – 11 February 2026 Shift 1 · Excretory system - kidney and nephron

Q81. In human beings, excretory products in the form of soluble nitrogen compounds are removed by the _____ in the kidneys.

  1. (a) nephrons
  2. (b) urethra
  3. (c) ATP
  4. (d) xylem
Answer & solution

Answer: (a) nephrons

The correct answer is nephrons (Option 1). Nephrons are the functional units of the kidney. They filter blood and remove soluble nitrogenous waste products (like urea) in the form of urine. Option 2 (urethra) is the tube through which urine passes out of the body, not the filtering unit. Option 3 (ATP) is an energy molecule, not related to excretion. Option 4 (xylem) is a plant tissue that transports water, not found in humans.
SSC MTS 2025 – 11 February 2026 Shift 3 · Lymphatic system

Q82. Lymph carries digested and absorbed fat from _____ and drains excess fluid from extra cellular space back into the blood.

  1. (a) liver
  2. (b) intestine
  3. (c) kidneys
  4. (d) pancreas
Answer & solution

Answer: (b) intestine

The correct answer is intestine (Option 2). Lymph (lymphatic fluid) carries digested and absorbed fats from the small intestine through specialized lymphatic vessels called lacteals, which are located in the villi of the small intestine. These fats (as chylomicrons) are transported via the thoracic duct into the bloodstream. Option 1 (liver) produces bile but is not the source of fat absorption into lymph. Options 3 and 4 are not related to fat absorption.
SSC MTS 2025 – 10 February 2026 Shift 2 · Excretory system - kidney and nephron

Q83. Where is urine stored before it is released from the human body?

  1. (a) In the kidneys
  2. (b) In the ureters
  3. (c) In the urinary bladder
  4. (d) In the urethra
Answer & solution

Answer: (c) In the urinary bladder

Correct Answer: 3 – In the urinary bladder.
After urine is produced in the kidneys, it travels through the ureters to the urinary bladder, where it is stored before being expelled from the body through the urethra. The urinary bladder is a muscular, hollow organ that can hold approximately 400–600 ml of urine.
The kidneys (Option 1) produce urine but do not store it.
The ureters (Option 2) are tubes that transport urine from the kidneys to the bladder.
The urethra (Option 4) is the tube through which urine is expelled from the body, not stored.
SSC MTS 2025 – 6 February 2026 Shift 1 · Heart - structure and functioning

Q84. Oxygen-rich blood from the lungs enters which of the following chamber of heart in humans?

  1. (a) Right atrium
  2. (b) Right ventricle
  3. (c) Left atrium
  4. (d) Left ventricle
Answer & solution

Answer: (c) Left atrium

Correct Answer: 3 (Left atrium)
Oxygenated blood from the lungs is carried by the pulmonary veins and enters the Left Atrium (left auricle) of the heart. From there, it passes to the Left Ventricle, which pumps it to the rest of the body through the aorta.
Option 1 (Right atrium) is incorrect - the Right Atrium receives deoxygenated blood from the body via superior and inferior vena cava.
Option 2 (Right ventricle) is incorrect - the Right Ventricle pumps deoxygenated blood to the lungs via the pulmonary artery.
Option 4 (Left ventricle) is incorrect - the Left Ventricle receives blood from the Left Atrium and pumps it to the body; it does not directly receive blood from the lungs.
SSC MTS 2025 – 6 February 2026 Shift 1 · Blood - components and functions

Q85. Which of the following component of blood stops bleeding?

  1. (a) Red blood cells
  2. (b) White blood cells
  3. (c) Plasma
  4. (d) Blood platelets
Answer & solution

Answer: (d) Blood platelets

Correct Answer: 4 (Blood platelets)
Blood platelets (thrombocytes) are responsible for stopping bleeding. When a blood vessel is injured, platelets aggregate at the wound site and initiate the clotting process (coagulation cascade), forming a blood clot that seals the wound.
Option 1 (Red blood cells) is incorrect - RBCs carry oxygen and do not play a role in clotting.
Option 2 (White blood cells) is incorrect - WBCs are responsible for immunity and fighting infections.
Option 3 (Plasma) is incorrect - Plasma is the liquid component of blood that carries nutrients, hormones, and proteins, but platelets are the primary agents that stop bleeding.
SSC MTS 2025 – 5 February 2026 Shift 2 · Blood vessels, circulation and blood pressure

Q86. What is the pressure of blood of human body inside the artery during ventricular systole called?

  1. (a) Diastolic pressure
  2. (b) Venous pressure
  3. (c) Systolic pressure
  4. (d) Capillary pressure
Answer & solution

Answer: (c) Systolic pressure

Correct Answer: Systolic pressure
Systolic pressure is the blood pressure in the arteries when the heart ventricles contract (systole) and pump blood into the arteries. It is the higher of the two blood pressure readings (e.g., 120 in '120/80 mmHg'). Normal systolic pressure is around 120 mmHg.
Why other options are wrong:
Diastolic pressure - Blood pressure when the heart is at rest between beats (relaxation phase); it is the lower reading.
Venous pressure - Pressure of blood within the veins; much lower than arterial pressure.
Capillary pressure - Pressure within capillaries; even lower and not measured routinely.
SSC MTS 2025 – 5 February 2026 Shift 3 · Human respiratory system

Q87. In humans, rings of cartilage are present in the ____.

  1. (a) stomach
  2. (b) mouth
  3. (c) ear
  4. (d) throat
Answer & solution

Answer: (d) throat

Correct Answer: throat
In humans, C-shaped rings of cartilage (tracheal rings or tracheal cartilages) are present in the trachea (windpipe), which passes through the throat/neck region. There are approximately 16-20 such rings that keep the trachea open and prevent it from collapsing during breathing.
Why other options are wrong:
Stomach - The stomach wall has smooth muscle layers, not cartilage rings.
Mouth - The mouth has no cartilage rings; it has teeth and tongue.
Ear - The outer ear (pinna) has elastic cartilage, but not 'rings of cartilage'.
Delhi Police Constable (Exe) 2025-26 – 6 January 2026 Shift 1 · Blood vessels, circulation and blood pressure

Q88. Which blood vessels in humans contain valves to prevent backflow of blood and ensure unidirectional circulation toward the heart?

  1. (a) Arteries
  2. (b) Veins
  3. (c) Capillaries
  4. (d) Aorta
Answer & solution

Answer: (b) Veins

The correct answer is (b) Veins.
Veins contain semilunar valves that prevent the backflow of blood and ensure that blood flows in one direction — toward the heart. These valves are particularly important in the veins of the legs, where blood must travel upward against gravity. When muscles contract, they compress the veins, pushing blood upward, and the valves prevent it from flowing back down.
(a) Arteries: Carry oxygenated blood away from the heart under high pressure; do not need valves because the high blood pressure from the heart keeps blood moving in one direction.
(c) Capillaries: Tiny blood vessels where exchange of gases, nutrients, and waste occurs between blood and tissues; too thin for valves; no valves present.
(d) Aorta: The largest artery in the body; carries oxygenated blood from the left ventricle; no valves inside its wall (the aortic valve is at its origin from the heart).
Delhi Police Constable (Exe) 2025-26 – 5 January 2026 Shift 3 · Blood - components and functions

Q89. Which blood component initiates clotting by releasing factors that trigger coagulation when a blood vessel is injured?

  1. (a) RBC
  2. (b) WBC
  3. (c) Platelets
  4. (d) Plasma
Answer & solution

Answer: (c) Platelets

The correct answer is (c) Platelets.
Platelets (thrombocytes) are tiny blood cells that initiate blood clotting. When a blood vessel is injured, platelets rush to the site, stick to the damaged area, and release chemical signals (ADP, thromboxane A2) that trigger the coagulation cascade, leading to clot formation to stop bleeding.
(a) RBC (Red Blood Cells): Carry oxygen using hemoglobin; do not initiate clotting.
(b) WBC (White Blood Cells): Part of the immune system; fight infections and foreign bodies; do not initiate clotting.
(d) Plasma: The liquid component of blood that carries blood cells, nutrients, and clotting factors; it participates in clotting but does not initiate it — platelets do.
Delhi Police Constable (Exe) 2025-26 – 29 December 2025 Shift 2 · Excretory system - kidney and nephron

Q90. In the nephron, the peritubular capillaries are primarily associated with which process?

  1. (a) Filtration
  2. (b) Reabsorption
  3. (c) Assimilation
  4. (d) Excretion
Answer & solution

Answer: (b) Reabsorption

The peritubular capillaries surround the renal tubules of the nephron and are primarily involved in reabsorption — the process by which useful substances (glucose, amino acids, water, salts) are reabsorbed from the filtrate back into the bloodstream. They also play a role in secretion of waste products.
(a) Incorrect: Filtration occurs at the glomerulus and Bowman's capsule, not at the peritubular capillaries.
(c) Incorrect: Assimilation refers to the body's use of absorbed nutrients; it is not a nephron-specific process.
(d) Incorrect: Excretion is the removal of metabolic wastes; peritubular capillaries specifically mediate reabsorption.
Delhi Police Constable (Exe) 2025-26 – 29 December 2025 Shift 2 · Excretory system - kidney and nephron

Q91. The collecting ducts of the nephron eventually drain into which structure?

  1. (a) Renal pelvis
  2. (b) Glomerulus
  3. (c) Ureter
  4. (d) Bowman's capsule
Answer & solution

Answer: (a) Renal pelvis

The collecting ducts converge and drain into the renal pelvis (the funnel-shaped cavity at the centre of the kidney). From the renal pelvis, urine passes into the ureter, then the urinary bladder, and finally out through the urethra. The glomerulus and Bowman's capsule are involved in filtration, not urine collection.
(b) Incorrect: Glomerulus is a capillary cluster involved in filtration of blood at the start of nephron function.
(c) Incorrect: The ureter connects the renal pelvis to the urinary bladder; collecting ducts drain into the pelvis first.
(d) Incorrect: Bowman's capsule surrounds the glomerulus and collects the initial filtrate, not the final urine from collecting ducts.
Delhi Police Constable (Exe) 2025-26 – 23 December 2025 Shift 1 · Aerobic and anaerobic respiration

Q92. What is the byproduct of anaerobic respiration in yeast?

  1. (a) Lactic acid
  2. (b) Ethanol and carbon dioxide
  3. (c) Water and oxygen
  4. (d) Glucose and pyruvate
Answer & solution

Answer: (b) Ethanol and carbon dioxide

The correct answer is Ethanol and carbon dioxide (Option 2).
In anaerobic respiration (fermentation), yeast breaks down glucose in the absence of oxygen to produce ethanol (alcohol) and carbon dioxide. This process is used in brewing, winemaking, and bread-making.
Option 1 - Lactic acid: Lactic acid is produced during anaerobic respiration in animal muscle cells (not in yeast).
Option 3 - Water and oxygen: Water and oxygen are not byproducts of anaerobic respiration; water is produced in aerobic respiration.
Option 4 - Glucose and pyruvate: Glucose is the starting reactant, not a byproduct. Pyruvate is an intermediate product in glycolysis before fermentation.
Delhi Police Constable (Exe) 2025-26 – 22 December 2025 Shift 1 · Aerobic and anaerobic respiration

Q93. What is the first step in breaking down glucose in cells?

  1. (a) Conversion of glucose into ethanol
  2. (b) Breakdown of glucose into pyruvate
  3. (c) Release of energy from pyruvate
  4. (d) Conversion of pyruvate into lactic acid
Answer & solution

Answer: (b) Breakdown of glucose into pyruvate

The first step in breaking down glucose in cells is glycolysis, which occurs in the cytoplasm. During glycolysis, one molecule of glucose (6-carbon) is broken down into two molecules of pyruvate (3-carbon each), producing 2 ATP and 2 NADH in the process. Option 2 is correct.
Option 1 is wrong: Conversion of glucose into ethanol (fermentation) is an anaerobic process that occurs in some microorganisms (like yeast), not the universal first step in cellular glucose breakdown; glycolysis always precedes it.
Option 3 is wrong: Release of energy from pyruvate (in the Krebs cycle and electron transport chain) occurs AFTER glycolysis; it is not the first step in glucose breakdown.
Option 4 is wrong: Conversion of pyruvate into lactic acid (lactic acid fermentation) occurs in muscle cells under anaerobic conditions as an alternative to aerobic respiration; it is not the first step in glucose breakdown.
SSC CPO Paper-1 2025 – 9 December 2025 Shift 1 · Aerobic and anaerobic respiration

Q94. Sequence the following stages of cellular respiration in the correct order:
1. Electron Transport Chain
2. Glycolysis
3. Krebs Cycle
4. Pyruvate Oxidation

  1. (a) 2 → 4 → 3 → 1
  2. (b) 1 → 2 → 3 → 4
  3. (c) 4 → 2 → 3 → 1
  4. (d) 3 → 2 → 1 → 4
Answer & solution

Answer: (a) 2 → 4 → 3 → 1

The correct sequence of cellular respiration is:
Glycolysis (Stage 2): Occurs in the cytoplasm; glucose is split into two pyruvate molecules, yielding small amounts of ATP and NADH.
Pyruvate Oxidation (Stage 4): Pyruvate enters the mitochondrial matrix and is converted to Acetyl-CoA, releasing CO₂ and NADH.
Krebs Cycle/Citric Acid Cycle (Stage 3): Acetyl-CoA enters the cycle; produces NADH, FADH₂, GTP (ATP), and CO₂.
Electron Transport Chain (Stage 1): NADH and FADH₂ donate electrons; a large amount of ATP is produced via oxidative phosphorylation.
Correct sequence: 2 → 4 → 3 → 1.
SSC Stenographer 2025 – 6 December 2025 Shift 1 · Blood - components and functions

Q95. What is the scientific term for white blood cells?

  1. (a) Thrombocytes
  2. (b) Platelets
  3. (c) Erythrocytes
  4. (d) Leucocytes
Answer & solution

Answer: (d) Leucocytes

The correct answer is Leucocytes . White blood cells (WBCs) are scientifically known as leucocytes. Their main function is to defend the body against infections, bacteria, viruses, and other foreign invaders. They form a crucial part of the immune system. There are several types of WBCs such as neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specialized roles in immunity. The term "Erythrocytes" refers to red blood cells (RBCs), which transport oxygen. "Thrombocytes" or platelets are responsible for blood clotting. Hence, the correct term for white blood cells is leucocytes.
SSC CHSL Tier-1 2025 – 30 November 2025 Shift 3 · Aerobic and anaerobic respiration

Q96. What are the end products of pyruvate during fermentation process?

  1. (a) Ethanol and carbon dioxide
  2. (b) Methanol and nitrogen
  3. (c) Methanol and hydrogen
  4. (d) Glucose and helium
Answer & solution

Answer: (a) Ethanol and carbon dioxide

Correct Answer: Option 1 – Ethanol and carbon dioxide
During fermentation (anaerobic respiration in yeast and some bacteria), pyruvate is converted into Ethanol (alcohol) and Carbon Dioxide. The reaction is: Pyruvate → Ethanol + CO2 ( catalysed by enzymes pyruvate decarboxylase and alcohol dehydrogenase). This process is used in brewing, baking, and biofuel production.
Why other options are wrong:
Option 2 (Methanol and nitrogen): Methanol is not produced in pyruvate fermentation; nitrogen is not a product.
Option 3 (Methanol and hydrogen): Incorrect; fermentation produces ethanol, not methanol.
Option 4 (Glucose and helium): Glucose is the starting material (substrate) of glycolysis, not a product; helium is an inert gas with no role in fermentation.
SSC CHSL Tier-1 2025 – 29 November 2025 Shift 1 · Blood - components and functions

Q97. In which cell is the respiratory pigment haemoglobin found in humans?

  1. (a) Red blood cells
  2. (b) Blood platelets
  3. (c) Monocytes
  4. (d) Nerve cells
Answer & solution

Answer: (a) Red blood cells

Haemoglobin is the respiratory pigment found in Red Blood Cells (RBCs/erythrocytes) in humans. It contains iron and is responsible for transporting oxygen from the lungs to the body's tissues.
Blood platelets help in clotting; Monocytes are white blood cells; Nerve cells transmit signals. Hence, Red blood cells is correct.
SSC CHSL Tier-1 2025 – 29 November 2025 Shift 3 · Human respiratory system

Q98. What structures are provided in the upper part of the respiratory tract to remove germs, dust, and other harmful particles from inhaled air in humans?

  1. (a) Alveoli
  2. (b) Bronchi
  3. (c) Pleura
  4. (d) Cilia
Answer & solution

Answer: (d) Cilia

Correct Answer: Option 4 – Cilia
Cilia are tiny hair-like structures lining the upper respiratory tract (nasal cavity, trachea, bronchi). They trap and sweep germs, dust, and harmful particles away from the lungs through a wave-like motion. Mucus produced by goblet cells traps the particles, and cilia move them up toward the throat where they are swallowed or expelled.
Why other options are wrong:
Option 1 (Alveoli): Alveoli are tiny air sacs in the lungs where gas exchange (O2 and CO2) occurs; they do not filter particles.
Option 2 (Bronchi): Bronchi are air-conducting tubes in the lungs; while they have cilia, the structures performing filtration are the cilia themselves.
Option 3 (Pleura): Pleura is the double-layered membrane surrounding the lungs; it provides protection, not filtration of air.
SSC CHSL Tier-1 2025 – 28 November 2025 Shift 1 · Blood vessels, circulation and blood pressure

Q99. What term is used for the pressure in the artery of human body during relaxation?

  1. (a) Diastolic pressure
  2. (b) Venous pressure
  3. (c) Systolic pressure
  4. (d) Capillary pressure
Answer & solution

Answer: (a) Diastolic pressure

Diastolic pressure is the term used for blood pressure in the arteries during the relaxation phase of the heart (diastole), when the heart muscle is relaxed and filling with blood. It is the lower number in a blood pressure reading (e.g., 80 in 120/80 mmHg).
Systolic pressure is during heart contraction; Venous pressure is in veins; Capillary pressure is in capillaries. Hence, Diastolic pressure is correct.
SSC CHSL Tier-1 2025 – 25 November 2025 Shift 2 · Heart - structure and functioning

Q100. Deoxygenated blood from the body enters through which of the following chamber of the heart of humans?

  1. (a) Right atrium
  2. (b) Right ventricle
  3. (c) Left atrium
  4. (d) Left ventricle
Answer & solution

Answer: (a) Right atrium

Deoxygenated blood from the body (systemic circulation) enters the heart through the Right atrium via the superior and inferior vena cava. From the right atrium, it passes to the right ventricle, which pumps it to the lungs for oxygenation.
Right ventricle pumps blood to the lungs; Left atrium receives oxygenated blood from the lungs; Left ventricle pumps oxygenated blood to the body.
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