Take the NUMS Biology — Digestion, Gaseous Exchange and Transport (Set 5): 30 multiple-choice questions (40 minutes) with instant scoring and a full…
The first 5 questions of this test, with the correct answer and explanation.
Q1. A resting person has a cardiac output of 5.25 L/min and a heart rate of 75 beats per minute. What is the stroke volume?
- A. 75 mL
- B. 70 mL ✓
- C. 60 mL
- D. 80 mL
Answer: B. 70 mL
Explanation: Stroke volume = cardiac output ÷ heart rate = 5250 mL ÷ 75 = 70 mL per beat.
Q2. A person's heart beats 90 times per minute. What is the approximate duration of one cardiac cycle?
- A. 0.67 s ✓
- B. 0.5 s
- C. 0.9 s
- D. 1.5 s
Answer: A. 0.67 s
Explanation: One cycle lasts 60 s ÷ 90 = 0.67 s.
Q3. A subject has a tidal volume of 500 mL, inspiratory reserve volume of 2500 mL, expiratory reserve volume of 1000 mL and residual volume of 1200 mL. What is the functional residual capacity?
- A. 3,000 mL
- B. 2,200 mL ✓
- C. 4,000 mL
- D. 1,500 mL
Answer: B. 2,200 mL
Explanation: FRC = expiratory reserve volume + residual volume = 1000 + 1200 = 2,200 mL. (3,000 mL is the inspiratory capacity and 4,000 mL the vital capacity.)
Q4. A man breathes 12 times a minute with a tidal volume of 500 mL; his anatomical dead space is 150 mL. What is his alveolar ventilation per minute?
- A. 4,800 mL
- B. 4,200 mL ✓
- C. 1,800 mL
- D. 6,000 mL
Answer: B. 4,200 mL
Explanation: Alveolar ventilation = (tidal volume − dead space) × rate = (500 − 150) × 12 = 4,200 mL/min.
Q5. At the same PO₂ of 30 mmHg, fetal blood is more saturated with oxygen than maternal blood. What explains this?
- A. Fetal haemoglobin has a higher O₂ affinity, so its curve is shifted left ✓
- B. Fetal haemoglobin has a higher O₂ affinity, so its curve is shifted right
- C. Fetal haemoglobin has a lower O₂ affinity, so its curve is shifted left
- D. Fetal blood has a lower pH, so its curve is shifted right
Answer: A. Fetal haemoglobin has a higher O₂ affinity, so its curve is shifted left
Explanation: Fetal Hb (α₂γ₂) binds O₂ more tightly than adult Hb, allowing oxygen to move from maternal to fetal blood across the placenta.
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Q6. A patient takes a drug that inhibits carbonic anhydrase in red blood cells. Which change in CO₂ transport is expected?
- A. More CO₂ is carried as bicarbonate, and tissue PCO₂ falls
- B. Less CO₂ is carried as bicarbonate, and tissue PCO₂ rises
- C. More CO₂ is carried as carboxyhaemoglobin, and blood pH rises
- D. Less CO₂ is carried as bicarbonate, and tissue PCO₂ falls
Q7. After spending three weeks at 4,500 m, a climber has a higher haematocrit than before. Which sequence explains this?
- A. Low O₂ → kidney releases erythropoietin → more red cells formed
- B. Low CO₂ → kidney releases erythropoietin → more red cells formed
- C. Low O₂ → liver releases thrombopoietin → more platelets formed
- D. Low O₂ → spleen releases renin → more white cells formed
Q8. A person holding their breath is forced to breathe again after about a minute. Which stimulus is chiefly responsible for the urge?
- A. Falling blood CO₂ detected by the carotid bodies, giving falling pH
- B. Rising blood CO₂ detected by chemoreceptors, giving falling pH
- C. Falling blood O₂ detected by the medulla, giving rising pH
- D. Rising blood O₂ detected by the aorta, giving rising pH
Q9. After a stab wound lets air into the pleural cavity, the lung on that side collapses. Why?
- A. Surfactant leaks from the lung, so the pleural fluid evaporates
- B. Alveolar pressure falls to zero, so the diaphragm cannot contract
- C. Intrapleural pressure falls below atmospheric, so the lung is sucked flat
- D. Intrapleural pressure rises to atmospheric, so the elastic lung recoils
Q10. A premature baby has laboured breathing and collapsed alveoli because its type II alveolar cells have not matured. What is deficient?
- A. Surfactant, which lowers the surface tension in the alveoli
- B. Mucus, which traps the dust particles in the alveoli
- C. Collagen, which raises the elastic recoil of the alveoli
- D. Haemoglobin, which carries the oxygen away from the alveoli
Q11. A gallstone blocks the common bile duct. Which combination of findings is expected?
- A. Pale fatty stools and poor absorption of vitamins A, D, E and K
- B. Pale fatty stools and poor absorption of vitamin C
- C. Dark fatty stools and poor absorption of amino acids
- D. Dark watery stools and poor absorption of the vitamin B group
Q12. Acidic chyme reaches the duodenum and the pH there falls to 3. Which response follows?
- A. Secretin is released, and the gallbladder secretes enzyme-rich juice
- B. Cholecystokinin is released, and the pancreas secretes bicarbonate only
- C. Secretin is released, and the pancreas secretes bicarbonate-rich juice
- D. Gastrin is released, and the stomach secretes more hydrochloric acid
Q13. A patient takes omeprazole, which blocks the H⁺/K⁺ ATPase of gastric parietal cells. What is the most direct effect?
- A. Gastric pH falls, and the secretion of mucus is reduced
- B. Gastric pH rises, and pepsinogen activation by acid is reduced
- C. Gastric pH falls, and pepsinogen activation by acid is increased
- D. Gastric pH rises, and the secretion of intrinsic factor is increased
Q14. An adult develops bloating, gas and watery diarrhoea after drinking milk. Which explanation is correct?
- A. Undigested lactose is absorbed whole and is toxic to the liver
- B. Undigested lactose reaches the colon and is fermented and osmotically active
- C. Undigested lactose reaches the stomach and is neutralised by acid
- D. Undigested casein reaches the colon and is broken down by bile
Q15. Intestinal epithelial cells are treated with ouabain, which blocks the Na⁺/K⁺ pump on their basolateral membrane. Glucose absorption from the lumen then falls because
- A. the chloride gradient driving glucose uptake is lost
- B. the glucose carriers on the apical side are digested
- C. the glucose is converted to fructose in the cells
- D. the sodium gradient driving glucose co-transport is lost
Q16. After a fat-rich meal, the lymph in the lacteals of the villi looks milky. The cloudiness is due to
- A. lipoproteins of cholesterol and amino acids made in the liver
- B. chylomicrons made of resynthesised triglycerides and protein
- C. bile salts attached to free fatty acids and glycerol
- D. micelles of monoglycerides made in the lumen of the duodenum
Q17. Which hormone, released from the duodenum in response to fat and protein products, causes the gallbladder to contract and the pancreas to release enzymes?
- A. Secretin
- B. Insulin
- C. Cholecystokinin
- D. Gastrin
Q18. In a potometer the air bubble moves 30 mm along a capillary of radius 1 mm. Taking π = 3.14, what volume of water was taken up?
- A. 94.2 mm³
- B. 31.4 mm³
- C. 188.4 mm³
- D. 30 mm³
Q19. A plant has most of its stomata on the lower leaf surface. Petroleum jelly is spread on the lower surface of some leaves and on the upper surface of others of the same size. Which result is expected?
- A. Leaves with a covered upper surface lose less water
- B. Both sets lose the same quantity of water
- C. Leaves with a covered lower surface lose less water
- D. Leaves with a covered lower surface lose more water
Q20. A stem is cut under water and the cut end remains submerged during a transpiration experiment. Why is cutting under water necessary?
- A. It prevents air entering the xylem and breaking the water column
- B. It keeps the stomata open and increases the transpiration
- C. It prevents water entering the phloem and blocking sugar flow
- D. It prevents roots from forming and increasing the uptake
Q21. In a girdling experiment, a ring of bark including the phloem is removed from a tree trunk. After some weeks, what is seen?
- A. A swelling above the ring, with leaves above starved of water
- B. A swelling below the ring, with leaves above starved of water
- C. A swelling below the ring, with roots below starved of sugar
- D. A swelling above the ring, with roots below starved of sugar
Q22. A leaf of a fruiting plant is supplied with ¹⁴CO₂. Which region will most probably become radioactive first outside the leaf?
- A. Mature leaves, via the xylem
- B. Old stem wood, via the phloem
- C. Developing fruits, via the phloem
- D. Root cap, via the xylem
Q23. During drought, abscisic acid is released in a leaf. What happens in the guard cells?
- A. K⁺ enters, turgor falls and the stomata close
- B. K⁺ enters, turgor rises and the stomata open
- C. K⁺ leaves, turgor rises and the stomata open
- D. K⁺ leaves, turgor falls and the stomata close
Q24. The aorta has a cross-sectional area of 3 cm² and blood flows through it at 30 cm/s. The total capillary cross-sectional area is 4,500 cm². What is the approximate blood velocity in the capillaries?
- A. 0.02 cm/s
- B. 2 cm/s
- C. 45 cm/s
- D. 0.2 cm/s
Q25. A patient on warfarin has a prolonged clotting time even though the platelet count is normal. Which mechanism of the drug explains this?
- A. It adds a calcium ion to plasma, which prevents fibrin cross-linking
- B. It destroys platelets, which stops the plug from forming
- C. It blocks vitamin K-dependent clotting factors, which slows fibrin formation
- D. It digests fibrin, which dissolves the formed clot
Q26. At the arteriole end of a capillary, hydrostatic pressure is 35 mmHg and plasma oncotic pressure is 25 mmHg. At the venule end the hydrostatic pressure is 15 mmHg. If the oncotic pressure falls to 15 mmHg because of low plasma albumin, what is the net force at the venule end?
- A. 10 mmHg outward, so fluid leaves the capillary
- B. 30 mmHg inward, so fluid returns to the capillary
- C. 0 mmHg, so no fluid returns to the capillary
- D. 10 mmHg inward, so fluid returns to the capillary
Q27. After the AV node is damaged by a heart attack, a patient has a slow ventricular rate, while the atria still beat at the normal rate. Which statement explains the finding?
- A. Impulses from the AV node fail to reach the atria, which beat on their own slower rhythm
- B. Impulses from the SA node fail to reach the ventricles, which beat on their own slower rhythm
- C. Impulses from the SA node fail to reach the atria, which beat on the ventricular rhythm
- D. Impulses from the Purkinje fibres fail to reach the SA node, which slows the atria
Q28. The wall of the left ventricle is much thicker than that of the right ventricle. What is the best explanation?
- A. It receives blood at higher pressure from the pulmonary artery
- B. It pumps blood at higher pressure around the whole body
- C. It pumps blood at higher pressure through the short lung circuit
- D. It stores more blood during diastole than the right ventricle
Q29. A man whose entire stomach was removed develops megaloblastic anaemia after several years, despite eating a normal diet. Which factor is missing?
- A. Pepsin, needed to absorb vitamin C
- B. Intrinsic factor, needed to absorb vitamin B₁₂
- C. Lipase, needed to absorb vitamin K
- D. Gastrin, needed to absorb folate in the ileum
Q30. Mangrove trees growing in waterlogged mud develop upward-growing roots (pneumatophores) with many pores. What is their function?
- A. Absorption of salt from the air by the roots
- B. Transport of sugars from the roots to the leaves
- C. Storage of starch for the roots in the mud
- D. Gas exchange for the roots in oxygen-poor mud