Free Human Digestive System MCQs with Answers

41. The acidic chyme entering the duodenum is neutralised by

• A. hydrochloric acid
• B. bicarbonate present in the pancreatic juice and bile
• C. pepsin
• D. salivary amylase

Explanation: Pancreatic bicarbonate raises the pH to around 8, the alkaline range in which pancreatic and intestinal enzymes work. Acid from the stomach would inactivate them, so neutralisation is essential.

42. The semi fluid mass of partly digested food in the stomach is called

• A. chyme
• B. bolus
• C. faeces
• D. bile

Explanation: Churning mixes food with gastric juice to form chyme, which is released in small amounts into the duodenum. The bolus is the earlier stage, the swallowed lump from the mouth.

43. The soft mass of chewed food formed in the mouth and swallowed is called the

• A. chyme
• B. plaque
• C. calculus
• D. bolus

Explanation: The tongue shapes moistened, chewed food into a slippery bolus sized for swallowing. Chyme comes later, in the stomach, so order of appearance separates the two.

44. In the small intestine, maltose is converted into glucose by the enzyme

• A. lipase
• B. trypsin
• C. maltase
• D. pepsin

Explanation: Maltase is one of the intestinal disaccharidases that finish carbohydrate digestion, alongside sucrase and lactase. Trypsin and pepsin act on protein, and lipase on fat.

45. Certain vitamins, including vitamin K, are synthesised for our benefit by

• A. the villi of the small intestine
• B. bacteria living in the large intestine
• C. the pancreas
• D. the gall bladder

Explanation: The resident flora of the colon manufacture vitamin K and some B vitamins, which are absorbed there, one reason the gut microbiome matters. Human tissues cannot make vitamin K themselves.

46. The elimination of undigested solid waste from the body is called

• A. defecation
• B. excretion
• C. secretion
• D. absorption

Explanation: Defecation, or egestion, removes material that never entered the body's tissues. Excretion is different: it removes metabolic wastes such as urea that came from inside cells.

47. Humans cannot digest cellulose because they

• A. find it toxic
• B. digest it before it reaches the stomach
• C. absorb it without digestion
• D. lack the enzyme cellulase

Explanation: The beta glycosidic bonds of cellulose need cellulase, which human cells do not produce, so it passes through as fibre. Ruminants rely on symbiotic microbes that supply the enzyme for them.

48. Inflammation of the blind ending tube attached to the caecum causes the condition known as

• A. ulcer
• B. hernia
• C. appendicitis
• D. cholera

Explanation: The vermiform appendix can become infected and swollen, producing pain in the lower right abdomen, and may need surgical removal. Cholera is an infection of the small intestine, and ulcers and hernias are unrelated structures.

49. Pepsin digests

• A. Carbohydrates
• B. Proteins
• C. Fats
• D. Nucleic acids

Explanation: Pepsin is a protease that digests proteins into peptides in the acidic environment of the stomach.

50. Bile is produced by the

• A. Gall bladder
• B. Liver
• C. Pancreas
• D. Stomach

Explanation: Bile is produced by the liver, stored in the gall bladder, and released into the duodenum.