Take the NUMS Biology — Digestion, Gaseous Exchange and Transport (Set 1): 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 patient whose gall bladder has been removed is advised to reduce fatty meals. This is because:
- A. Fats are absorbed only in the stomach
- B. Lipase can no longer be produced
- C. Insulin secretion stops
- D. Bile is no longer stored and released in large amounts to emulsify fats ✓
Answer: D. Bile is no longer stored and released in large amounts to emulsify fats
Explanation: Bile still forms in the liver but trickles continuously; a large fatty meal cannot be emulsified efficiently without stored bile.
Q2. Bile helps fat digestion mainly by:
- A. Neutralising lipase activity
- B. Emulsifying fats into small droplets, increasing surface area for lipase ✓
- C. Hydrolysing fats into fatty acids and glycerol
- D. Converting fats into glucose
Answer: B. Emulsifying fats into small droplets, increasing surface area for lipase
Explanation: Bile salts contain no enzymes; they emulsify fats so pancreatic lipase can act on a larger surface area.
Q3. Pepsin is secreted as inactive pepsinogen. The main advantage of this is that:
- A. It makes pepsin work faster in alkaline conditions
- B. It allows pepsin to digest starch
- C. It prevents pepsin from being destroyed by bile
- D. It prevents the enzyme from digesting the cells that produce it ✓
Answer: D. It prevents the enzyme from digesting the cells that produce it
Explanation: Secreting proteases as inactive zymogens protects the chief cells; HCl converts pepsinogen to pepsin in the stomach lumen.
Q4. Enterokinase secreted by the duodenal wall is needed to:
- A. Convert trypsinogen into active trypsin ✓
- B. Convert pepsinogen into pepsin
- C. Emulsify fats
- D. Digest maltose into glucose
Answer: A. Convert trypsinogen into active trypsin
Explanation: Enterokinase (enteropeptidase) activates trypsinogen; trypsin then activates other pancreatic zymogens.
Q5. Which hormone stimulates the pancreas to release a bicarbonate-rich juice when acidic chyme enters the duodenum?
- A. Gastrin
- B. Secretin ✓
- C. Insulin
- D. Cholecystokinin
Answer: B. Secretin
Explanation: Acid in the duodenum triggers secretin, which causes the pancreas to secrete bicarbonate to neutralise the chyme.
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Q6. Fatty acids and monoglycerides absorbed into intestinal epithelial cells are reassembled into triglycerides and enter:
- A. The stomach
- B. The lacteals as chylomicrons
- C. The large intestine
- D. The hepatic portal vein directly as free fatty acids
Q7. The function of villi and microvilli in the small intestine is to:
- A. Produce peristaltic waves
- B. Greatly increase the surface area for absorption
- C. Store bile
- D. Secrete hydrochloric acid
Q8. A peptic ulcer is most commonly associated with infection by:
- A. Vibrio cholerae
- B. Helicobacter pylori
- C. Escherichia coli
- D. Salmonella typhi
Q9. Which statement about the large intestine is correct?
- A. It is the main site of protein digestion
- B. It contains villi for fat absorption
- C. It absorbs most of the remaining water and some vitamins made by bacteria
- D. It secretes pancreatic amylase
Q10. During inspiration in humans:
- A. Pressure in the lungs rises above atmospheric pressure
- B. The diaphragm contracts and flattens, and external intercostals raise the ribs
- C. Internal intercostals contract to lower the ribs
- D. The diaphragm relaxes and becomes dome-shaped
Q11. Most carbon dioxide is transported in human blood as:
- A. Carbaminohaemoglobin
- B. Bicarbonate ions in the plasma
- C. Carbonic acid inside platelets
- D. Dissolved CO₂ in plasma
Q12. As bicarbonate ions diffuse out of red blood cells into the plasma, chloride ions move in. This is called:
- A. Bohr effect
- B. Haldane effect
- C. Chloride shift
- D. Osmoregulation
Q13. In actively respiring muscle, higher CO₂ and lower pH shift the oxygen dissociation curve to the right. This means:
- A. Less oxygen is delivered to muscles
- B. Haemoglobin releases oxygen more readily to the tissues
- C. Haemoglobin binds oxygen more tightly
- D. Carbon monoxide binding is reduced
Q14. Fetal haemoglobin has a dissociation curve to the left of adult haemoglobin. This allows the fetus to:
- A. Carry more carbon dioxide than oxygen
- B. Avoid needing oxygen at all
- C. Take oxygen from maternal blood across the placenta
- D. Release oxygen faster to the mother
Q15. Carbon monoxide is dangerous because it:
- A. Shifts the dissociation curve to the right
- B. Destroys red blood cells by lysis
- C. Blocks the trachea
- D. Binds haemoglobin far more strongly than oxygen, forming carboxyhaemoglobin
Q16. Breathing rate rises during exercise mainly because chemoreceptors detect:
- A. A decrease in blood glucose
- B. An increase in blood CO₂ and H⁺ concentration
- C. An increase in blood oxygen
- D. A fall in body temperature
Q17. In emphysema, the walls of alveoli break down. The main effect is:
- A. Reduced surface area for gas exchange, causing breathlessness
- B. Increased elasticity of lungs
- C. Narrowing of the trachea only
- D. Increased oxygen uptake
Q18. Surfactant secreted in the alveoli is important because it:
- A. Carries oxygen across the membrane
- B. Increases surface tension to aid recoil
- C. Kills inhaled bacteria
- D. Lowers surface tension, preventing alveoli from collapsing
Q19. Which feature of the alveolus does NOT directly increase the rate of diffusion of gases?
- A. Rich capillary network maintaining a gradient
- B. Presence of cartilage rings
- C. Very thin walls
- D. Large total surface area
Q20. Stomata of a plant open when guard cells:
- A. Lose water by osmosis
- B. Accumulate abscisic acid
- C. Lose K⁺ ions and become flaccid
- D. Take up K⁺ ions, lower their water potential and become turgid
Q21. The cohesion-tension theory explains water movement in xylem as mainly being caused by:
- A. Pressure from phloem sieve tubes
- B. Root pressure alone
- C. Active pumping by xylem vessels
- D. Transpiration pull from the leaves acting on a continuous column of water
Q22. The Casparian strip in the endodermis of roots forces water and solutes to:
- A. Flow back to the cortex
- B. Pass through the cytoplasm of endodermal cells (symplast) rather than the cell walls
- C. Move only through dead xylem cells
- D. Enter the phloem directly
Q23. In the pressure-flow (mass flow) hypothesis, sucrose moves in phloem from source to sink because:
- A. Loading sucrose at the source draws in water, creating high pressure that pushes sap towards the sink
- B. Xylem vessels pump sucrose upward
- C. Phloem cells are dead and empty
- D. Sucrose diffuses only from root to leaf
Q24. A ring of bark (including phloem) is removed from a tree trunk. After some weeks the bark just above the ring swells. This shows that:
- A. Sugars are transported downward in the phloem
- B. Minerals move through the bark
- C. Xylem carries sugars downward
- D. Water moves upward in the phloem
Q25. Which factor would decrease the rate of transpiration?
- A. Increase in temperature
- B. Increase in light intensity
- C. Increase in wind speed
- D. High humidity of the surrounding air
Q26. The sinoatrial (SA) node is called the pacemaker because it:
- A. Carries impulses down the septum
- B. Generates impulses that initiate each heartbeat
- C. Closes the semilunar valves
- D. Delays impulses between atria and ventricles
Q27. The delay of the impulse at the atrioventricular (AV) node is important because it:
- A. Speeds up the heart rate
- B. Prevents the SA node from firing
- C. Allows the atria to finish contracting before the ventricles contract
- D. Lets both atria and ventricles contract together
Q28. The 'lub' sound of the heartbeat is produced by:
- A. Opening of the semilunar valves
- B. Closure of the atrioventricular valves at the start of ventricular systole
- C. Closure of the semilunar valves
- D. Contraction of the atria
Q29. Which blood vessel carries oxygenated blood?
- A. Pulmonary vein
- B. Pulmonary artery
- C. Superior vena cava
- D. Hepatic portal vein
Q30. Tissue fluid forms at the arterial end of a capillary because:
- A. Osmotic pressure exceeds hydrostatic pressure
- B. Red blood cells squeeze out of the capillary
- C. Lymph is pumped into the capillary
- D. Hydrostatic pressure of the blood exceeds the osmotic pressure of plasma proteins