Take the NUMS Biology — Digestion, Gaseous Exchange and Transport (Set 4): 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 heart rate of 72 beats per minute and a stroke volume of 70 mL. What is the cardiac output?
- A. About 5.0 L/min ✓
- B. About 1.0 L/min
- C. About 0.5 L/min
- D. About 7.2 L/min
Answer: A. About 5.0 L/min
Explanation: Cardiac output = heart rate × stroke volume = 72 × 70 = 5040 mL ≈ 5.0 L/min.
Q2. When heart rate rises from 75 to 100 beats/min, the duration of ventricular systole stays at about 0.3 s. By how much does the cycle length change, and what happens to diastole?
- A. The cycle rises to 1.0 s and diastole lengthens
- B. The cycle falls from 0.8 s to 0.6 s, and diastole is unchanged
- C. The cycle falls to 0.6 s and systole shortens to 0.1 s
- D. The cycle falls from 0.8 s to 0.6 s, and diastole shortens from 0.5 s to 0.3 s ✓
Answer: D. The cycle falls from 0.8 s to 0.6 s, and diastole shortens from 0.5 s to 0.3 s
Explanation: Cycle = 60/75 = 0.8 s and 60/100 = 0.6 s. With systole fixed at 0.3 s, diastole = 0.5 s then 0.3 s: faster rates shorten mainly diastole.
Q3. A spirometer trace gives tidal volume 500 mL, inspiratory reserve 3000 mL, expiratory reserve 1100 mL and residual volume 1200 mL. What are the vital capacity and the functional residual capacity?
- A. VC = 4600 mL; FRC = 1200 mL
- B. VC = 4600 mL; FRC = 2300 mL ✓
- C. VC = 3500 mL; FRC = 5800 mL
- D. VC = 5800 mL; FRC = 2300 mL
Answer: B. VC = 4600 mL; FRC = 2300 mL
Explanation: VC = TV + IRV + ERV = 4600 mL; FRC = ERV + RV = 2300 mL; TLC = VC + RV = 5800 mL.
Q4. A person breathes 12 times per minute with a tidal volume of 500 mL. Anatomical dead space is 150 mL. What is the alveolar ventilation per minute?
- A. 6000 mL
- B. 3000 mL
- C. 4200 mL ✓
- D. 1800 mL
Answer: C. 4200 mL
Explanation: Alveolar ventilation = (tidal volume − dead space) × rate = (500 − 150) × 12 = 4200 mL/min; 6000 mL is the total minute ventilation.
Q5. A patient has FEV₁ = 1.5 L and FVC = 4.5 L. What is the FEV₁/FVC ratio, and what does it suggest?
- A. 33%, suggesting an obstructive disease such as emphysema or asthma ✓
- B. 300%, suggesting increased compliance with healthy airways
- C. 33%, suggesting normal lungs because FVC is within the normal range
- D. 67%, suggesting a restrictive disease such as pulmonary fibrosis
Answer: A. 33%, suggesting an obstructive disease such as emphysema or asthma
Explanation: 1.5/4.5 = 0.33, well below the normal ~0.75–0.80, so airflow is obstructed; the ratio is preserved or high in restrictive disease.
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Q6. In which condition is the oxygen dissociation curve of haemoglobin shifted to the right, and what is the benefit?
- A. In myoglobin, to store O₂
- B. In the lungs with low CO₂, increasing O₂ loading
- C. In the fetus, to take O₂ from the mother
- D. In active muscle with raised CO₂ and H⁺, releasing more O₂ to tissues
Q7. Fetal haemoglobin has a higher oxygen affinity than adult haemoglobin. How does this help the fetus?
- A. Its curve lies to the left, so it picks up O₂ from maternal blood at the placenta
- B. Its curve lies to the right, so it releases O₂ in the placenta
- C. It does not need to release O₂ to tissues
- D. It binds carbon dioxide only
Q8. About 70% of CO₂ is carried by blood as bicarbonate. Which sequence of events in a red blood cell in tissues is correct?
- A. CO₂ + H₂O → H₂CO₃ (carbonic anhydrase) → H⁺ + HCO₃⁻; HCO₃⁻ leaves and Cl⁻ enters
- B. H₂CO₃ forms in plasma and Cl⁻ leaves the cell
- C. CO₂ binds to carboxyhaemoglobin and HCO₃⁻ enters the cell
- D. HCO₃⁻ enters the cell as Na⁺ leaves
Q9. A potometer capillary has a radius of 0.5 mm. The air bubble moves 120 mm in 5 minutes. What is the approximate water uptake rate? (π ≈ 3.14)
- A. 38 mm³ per minute
- B. 94 mm³ per minute
- C. 9.4 mm³ per minute
- D. 19 mm³ per minute
Q10. Cell A has water potential −0.5 MPa, cell B −0.8 MPa and cell C −0.3 MPa, and the three are adjacent in a row A–B–C. In which direction does water move through the symplast?
- A. No net movement
- B. From B to A to C
- C. From C to A to B
- D. From A to C and B
Q11. A potted plant is kept in a draught of dry moving air. Compared with still humid air, what happens to transpiration and why?
- A. It increases, because the diffusion gradient of water vapour is steeper
- B. It stops, because the leaf loses turgor immediately
- C. It is unchanged, because transpiration depends only on soil water
- D. It decreases, because wind closes all stomata at once
Q12. A ring of bark including phloem is removed from a tree trunk. Several weeks later, where do sugars accumulate?
- A. In the xylem only
- B. Above the ring, so the bark swells there
- C. Below the ring, so the bark swells there
- D. Equally above and below the ring
Q13. Radioactive ¹⁴CO₂ is given to a single leaf. Which tissue will first carry labelled sucrose out of that leaf?
- A. Tracheids
- B. Collenchyma
- C. Xylem vessels
- D. Phloem sieve tubes
Q14. A patient has a gallstone blocking the bile duct. Which combination of symptoms and consequences is expected?
- A. Dark stools and poor protein digestion
- B. Pale stools and excess bile salts in the blood only
- C. Pale fatty stools and poor absorption of vitamins A, D, E and K
- D. Poor starch digestion and low blood sugar
Q15. Dilute acid is introduced into the duodenum of an experimental animal. Which sequence correctly describes the response?
- A. Cholecystokinin is released, stimulating parietal cells
- B. Secretin is released, stimulating the pancreas to release bicarbonate-rich juice
- C. Insulin is released, stimulating the pancreas to release pepsin
- D. Gastrin is released, stimulating the liver to release bile salts
Q16. The drug ouabain blocks Na⁺/K⁺-ATPase in intestinal epithelial cells. What is the effect on glucose absorption?
- A. It falls only in the stomach
- B. It is unchanged, because glucose crosses by simple diffusion
- C. It falls, because the sodium gradient driving glucose co-transport is lost
- D. It rises, because glucose then enters by osmosis
Q17. A child develops bloating, gas and watery diarrhoea after drinking milk. The most likely cause is
- A. deficiency of lactase, leaving lactose to be fermented by gut bacteria and to draw water into the lumen
- B. failure of the pancreas to secrete amylase, leaving starch to be fermented by gut bacteria
- C. excess of bile salts reaching the colon, which irritate the lining and draw water into the lumen
- D. deficiency of pepsin, leaving protein undigested to be fermented by gut bacteria and cause watery stools
Q18. A drug used for peptic ulcers inhibits the H⁺/K⁺-ATPase. In which cells does it act and what is the immediate effect?
- A. Chief cells, reducing pepsinogen secretion
- B. Parietal cells, reducing secretion of hydrochloric acid
- C. Goblet cells, reducing mucus
- D. G cells, reducing gastrin secretion
Q19. Why are pepsinogen and trypsinogen secreted as inactive precursors but amylase of saliva is not?
- A. Proteases could digest the cells and ducts that make them, while amylase acts on carbohydrate, not cell protein
- B. Amylase needs a cofactor not present in the gland, so it can only be activated in the mouth
- C. Amylase is made only in the duodenum, so there is no risk of it digesting the cells that secrete it
- D. Pepsinogen is a hormone, not an enzyme, so it must be released in an inactive form like insulin
Q20. A drug inhibits vitamin K action in the liver. Which effect on blood clotting is expected?
- A. No change in clotting, since calcium ions are the only cofactor needed by clotting factors
- B. Reduced platelet count only, with no change in the amounts of clotting factors made
- C. Prolonged clotting time because prothrombin and other factors are not made properly
- D. Faster clotting because fibrinogen increases when vitamin K action is blocked in the liver
Q21. On an ECG a P wave occurs but is not followed by a QRS complex at regular intervals. Which part of the conducting system is likely blocked?
- A. Sinoatrial node, since without it the atria cannot generate any impulse and no P wave appears
- B. Atrioventricular node or bundle, so the atrial impulse does not reach the ventricles
- C. Purkinje fibres only, so the atria stop contracting while the ventricles continue normally
- D. Bicuspid valve, so blood flows backward into the atria and the QRS complex is lost
Q22. At the arteriolar end of a capillary, hydrostatic pressure is 35 mmHg and oncotic pressure 25 mmHg; at the venular end hydrostatic pressure is 15 mmHg. What are the net movements of fluid at the two ends?
- A. 10 mmHg in at the arteriolar end and 10 mmHg out at the venular end
- B. 10 mmHg out at the arteriolar end and 10 mmHg in at the venular end
- C. No net movement at either end
- D. 25 mmHg out at the arteriolar end and 15 mmHg in at the venular end
Q23. A severely malnourished child has swollen legs and abdomen. Which change in the blood best explains the accumulation of tissue fluid?
- A. Low plasma albumin lowers oncotic pressure, so less fluid is reabsorbed at the venular end
- B. Increased lymph flow drains the tissues too quickly, so fluid collects in the lymph vessels
- C. High red blood cell count blocks the capillaries, so fluid cannot return to the circulation
- D. High plasma albumin raises the hydrostatic pressure, so fluid is forced out of the capillaries
Q24. A person holds their breath and the urge to breathe grows. Which stimulus mainly drives this urge?
- A. Rising O₂ detected by the carotid body, which stimulates the medulla to increase breathing
- B. Falling blood glucose detected by the aortic body, which signals the medulla to breathe faster
- C. Falling O₂ detected only by chemoreceptors in the medulla, which are the main drive to breathe
- D. Rising CO₂ lowering the pH of cerebrospinal fluid, detected by medullary chemoreceptors
Q25. A person hyperventilates voluntarily for a minute. What change in blood occurs and why might they feel dizzy?
- A. Blood CO₂ rises and pH falls, causing vasodilation
- B. Blood CO₂ falls and pH rises, causing vasoconstriction in the brain
- C. Blood bicarbonate disappears completely
- D. Blood O₂ falls sharply because of breathlessness
Q26. Emphysema causes the walls between alveoli to break down. Which result follows?
- A. Increased surface area and improved diffusion
- B. Blocked bronchioles due to mucus plugs only
- C. Lower residual volume
- D. Reduced surface area for gas exchange and loss of elastic recoil
Q27. A drop of fat of radius 1 cm is broken into 8 equal droplets that together have the same volume. By what factor does the total surface area increase?
Q28. Bilirubin from the breakdown of haemoglobin is conjugated in the liver. In obstructive jaundice which findings are expected?
- A. Dark stools and pale urine with raised unconjugated bilirubin
- B. Normal stools and dark urine with raised unconjugated bilirubin
- C. Pale stools and pale urine with raised conjugated bilirubin
- D. Pale stools and dark urine with raised conjugated bilirubin
Q29. Leaves from a plant are found to have most stomata on the lower surface. How does this suit a land plant?
- A. It prevents any water loss at all, because the lower surface is always shaded and cool
- B. Stomata on the lower side absorb water from the soil through the leaf and petiole
- C. Less direct sunlight and heat on the lower surface reduce water loss while CO₂ still enters
- D. More light falls on the lower surface, which speeds up photosynthesis in the guard cells there
Q30. Pressures recorded at one instant are: left atrium 10 mmHg, left ventricle 5 mmHg, aorta 80 mmHg. What is the state of the valves?
- A. Bicuspid valve open and aortic semilunar valve closed
- B. Both valves open
- C. Bicuspid valve closed and aortic valve open
- D. Both valves closed