IMO Practice Test — Digestion and Absorption
6 Questions • 15 min • Olympiad level
15:00
Question 1 of 6
Salivary amylase stops working when food reaches the stomach because the stomach is:
Strongly acidic, which denatures the enzyme
Too alkaline
Too cold
Full of bile
Explanation: The acidic gastric environment denatures salivary amylase, which works best near neutral pH.
Question 2 of 6
A person whose gall bladder is removed may struggle to digest fatty meals because they lack stored:
Bile to emulsify fats
Pepsin
Saliva
Hydrochloric acid
Explanation: Bile (stored in the gall bladder) emulsifies fats; without it, fat digestion is harder.
Question 3 of 6
The small intestine's length, folds and villi all serve to:
Maximise the surface area for absorption
Speed up peristalsis only
Make HCl
Produce bile
Explanation: These features greatly increase surface area, making absorption efficient.
Question 4 of 6
Why must proteins be digested to amino acids before they can enter the blood?
Large protein molecules cannot cross the intestinal wall
Amino acids are poisonous
Blood cannot carry protein
Proteins dissolve villi
Explanation: Only small, soluble molecules like amino acids can be absorbed through the gut wall.
Question 5 of 6
A diet very low in fibre most directly increases the risk of:
Constipation
Jaundice
Diabetes
Anaemia
Explanation: Fibre adds bulk and helps the gut move waste; too little causes constipation.
Question 6 of 6
Pepsin is secreted as an inactive form and activated only in the stomach. This protects the body by:
Preventing the enzyme from digesting the cells that make it
Making more acid
Speeding absorption
Emulsifying fat
Explanation: Storing it inactive stops the protein-digesting enzyme from damaging the gland cells before it is needed.