Part 3: Digestion of Food (25 MCQs)

Q1. The digestion of starch begins in:

A. Mouth
B. Stomach
C. Duodenum
D. Ileum

Answer: A

Explanation:

A. Correct: Salivary amylase begins starch digestion in the mouth.
B. Incorrect: Stomach secretes no amylase.
C. Incorrect: Duodenum continues carbohydrate digestion, but does not start it.
D. Incorrect: Ileum is for absorption, not digestion.

Q2. Pepsin acts in which medium?

A. Strongly alkaline
B. Weakly alkaline
C. Acidic
D. Neutral

Answer: C

Explanation:

A. Incorrect: Alkaline medium inactivates pepsin.
B. Incorrect: Pepsin needs low pH.
C. Correct: Pepsin works optimally at pH 1.5–2.0.
D. Incorrect: Neutral medium does not support pepsin.

Q3. Rennin, an enzyme in infants, helps in digestion of:

A. Carbohydrates
B. Proteins (milk casein)
C. Fats
D. Nucleic acids

Answer: B

Explanation:

A. Incorrect: Amylase digests carbohydrates.
B. Correct: Rennin coagulates milk protein (casein) in infants.
C. Incorrect: Lipase digests fats.
D. Incorrect: Nucleases digest nucleic acids.

Q4. Which enzyme converts proteins into peptones in the stomach?

A. Trypsin
B. Pepsin
C. Erepsin
D. Rennin

Answer: B

Explanation:

A. Incorrect: Trypsin acts in the small intestine.
B. Correct: Pepsin digests proteins into peptones and proteoses.
C. Incorrect: Erepsin digests peptides into amino acids.
D. Incorrect: Rennin only curdles milk in infants.

Q5. Which of the following is NOT digested by pancreatic juice?

A. Proteins
B. Fats
C. Carbohydrates
D. Cellulose

Answer: D

Explanation:

A. Incorrect: Trypsin/chymotrypsin digest proteins.
B. Incorrect: Lipase digests fats.
C. Incorrect: Amylase digests starch.
D. Correct: Humans lack cellulase, so cellulose is not digested.

Q6. The end-products of carbohydrate digestion are:

A. Disaccharides
B. Monosaccharides
C. Polysaccharides
D. Amino acids

Answer: B

Explanation:

A. Incorrect: Disaccharides are intermediate.
B. Correct: Glucose, fructose, and galactose are final products.
C. Incorrect: Polysaccharides are broken down, not end products.
D. Incorrect: Amino acids are products of protein digestion.

Q7. Trypsin acts upon:

A. Starch
B. Proteins/Peptides
C. Fats
D. Nucleic acids

Answer: B

Explanation:

A. Incorrect: Starch is digested by amylase.
B. Correct: Trypsin digests proteins into peptides.
C. Incorrect: Fats are digested by lipase.
D. Incorrect: Nucleic acids are digested by nucleases.

Q8. Fat digestion requires the action of:

A. Pepsin
B. Bile salts and lipase
C. Amylase and lipase
D. Trypsin and bile pigments

Answer: B

Explanation:

A. Incorrect: Pepsin digests proteins.
B. Correct: Bile salts emulsify fats; lipase digests them.
C. Incorrect: Amylase acts on starch, not fats.
D. Incorrect: Bile pigments have no role in digestion.

Q9. Which enzyme converts maltose into glucose?

A. Lactase
B. Maltase
C. Sucrase
D. Amylase

Answer: B

Explanation:

A. Incorrect: Lactase acts on lactose.
B. Correct: Maltase hydrolyzes maltose into 2 glucose units.
C. Incorrect: Sucrase hydrolyzes sucrose.
D. Incorrect: Amylase breaks starch into maltose, not maltose into glucose.

Q10. Which of the following is an exopeptidase?

A. Pepsin
B. Trypsin
C. Carboxypeptidase
D. Endopeptidase

Answer: C

Explanation:

A. Incorrect: Pepsin is an endopeptidase.
B. Incorrect: Trypsin is an endopeptidase.
C. Correct: Carboxypeptidase removes amino acids from peptide ends.
D. Incorrect: Endopeptidases cut internal peptide bonds.

Q11. Which enzyme is absent in gastric juice?

A. Pepsin
B. Lipase
C. Amylase
D. Rennin

Answer: C

Explanation:

A. Incorrect: Pepsin is present.
B. Incorrect: Gastric lipase is present in small quantity.
C. Correct: Amylase is not secreted in gastric juice.
D. Incorrect: Rennin is present in infants.

Q12. Which of the following is activated by enterokinase?

A. Pepsinogen
B. Trypsinogen
C. Procarboxypeptidase
D. Amylase

Answer: B

Explanation:

A. Incorrect: Pepsinogen is activated by HCl.
B. Correct: Enterokinase activates trypsinogen to trypsin.
C. Incorrect: Procarboxypeptidase is activated by trypsin.
D. Incorrect: Amylase is secreted in active form.

Q13. Protein digestion starts in:

A. Mouth
B. Stomach
C. Duodenum
D. Ileum

Answer: B

Explanation:

A. Incorrect: Mouth has no protease.
B. Correct: Pepsin begins protein digestion in stomach.
C. Incorrect: Duodenum continues digestion but does not start it.
D. Incorrect: Ileum is mainly for absorption.

Q14. Which of the following is a brush-border enzyme?

A. Sucrase
B. Amylase
C. Lipase
D. Pepsin

Answer: A

Explanation:

A. Correct: Sucrase is present on intestinal brush border.
B. Incorrect: Amylase is secreted in saliva/pancreas.
C. Incorrect: Lipase is secreted by pancreas.
D. Incorrect: Pepsin is secreted in stomach.

Q15. The digestion of nucleic acids occurs mainly in:

A. Mouth
B. Stomach
C. Small intestine
D. Large intestine

Answer: C

Explanation:

A. Incorrect: Mouth has no nuclease.
B. Incorrect: Stomach has no nuclease.
C. Correct: Pancreatic nucleases digest DNA/RNA in small intestine.
D. Incorrect: Large intestine is mainly for absorption of water.

Q16. Which enzyme digests milk sugar (lactose)?

A. Maltase
B. Lactase
C. Sucrase
D. Amylase

Answer: B

Explanation:

A. Incorrect: Maltase digests maltose.
B. Correct: Lactase digests lactose into glucose + galactose.
C. Incorrect: Sucrase digests sucrose.
D. Incorrect: Amylase digests starch.

Q17. Which factor is essential for activation of pepsinogen?

A. Bile salts
B. Hydrochloric acid
C. Secretin
D. Enterokinase

Answer: B

Explanation:

A. Incorrect: Bile salts emulsify fats.
B. Correct: HCl activates pepsinogen into pepsin.
C. Incorrect: Secretin stimulates pancreas, not pepsinogen.
D. Incorrect: Enterokinase activates trypsinogen.

Q18. Which one is NOT a product of fat digestion?

A. Glycerol
B. Fatty acids
C. Monoglycerides
D. Amino acids

Answer: D

Explanation:

A. Correct product.
B. Correct product.
C. Correct product.
D. Correct answer: Amino acids are products of protein digestion.

Q19. Which enzyme hydrolyzes sucrose?

A. Maltase
B. Sucrase
C. Lactase
D. Amylase

Answer: B

Explanation:

A. Incorrect: Maltase acts on maltose.
B. Correct: Sucrase hydrolyzes sucrose into glucose + fructose.
C. Incorrect: Lactase hydrolyzes lactose.
D. Incorrect: Amylase acts on starch.

Q20. Which of the following is secreted in inactive form?

A. Amylase
B. Lipase
C. Pepsinogen
D. Maltase

Answer: C

Explanation:

A. Incorrect: Amylase is secreted active.
B. Incorrect: Lipase is secreted active.
C. Correct: Pepsinogen is secreted inactive to avoid autodigestion.
D. Incorrect: Maltase is active.

Q21. Carbohydrate digestion does NOT occur in:

A. Mouth
B. Stomach
C. Duodenum
D. Jejunum

Answer: B

Explanation:

A. Incorrect: Mouth has salivary amylase.
B. Correct: Stomach lacks amylase.
C. Incorrect: Duodenum has pancreatic amylase.
D. Incorrect: Jejunum has disaccharidases.

Q22. Protein digestion is completed in:

A. Stomach
B. Duodenum
C. Jejunum
D. Ileum

Answer: C

Explanation:

A. Incorrect: Stomach begins protein digestion but does not complete.
B. Incorrect: Duodenum partially digests proteins.
C. Correct: Jejunum completes protein digestion into amino acids.
D. Incorrect: Ileum absorbs but does not digest much.

Q23. Lingual lipase is secreted by:

A. Stomach
B. Salivary glands (tongue)
C. Pancreas
D. Duodenum

Answer: B

Explanation:

A. Incorrect: Stomach secretes gastric lipase.
B. Correct: Lingual glands on tongue secrete lingual lipase.
C. Incorrect: Pancreas secretes pancreatic lipase.
D. Incorrect: Duodenum has no lipase.

Q24. Which enzyme digests peptides into amino acids in the small intestine?

A. Trypsin
B. Pepsin
C. Erepsin
D. Rennin

Answer: C

Explanation:

A. Incorrect: Trypsin digests proteins into peptides, not amino acids fully.
B. Incorrect: Pepsin acts in stomach.
C. Correct: Erepsin (peptidases) digest peptides into amino acids.
D. Incorrect: Rennin curdles milk.

Q25. End-products of fat digestion are absorbed as:

A. Amino acids
B. Monosaccharides
C. Micelles (fatty acids + monoglycerides)
D. Peptides

Answer: C

Explanation:

A. Incorrect: Amino acids come from protein digestion.
B. Incorrect: Monosaccharides come from carbohydrate digestion.
C. Correct: Fats are absorbed as micelles containing fatty acids and monoglycerides.
D. Incorrect: Peptides are intermediates of protein digestion.

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Part 3: Digestion of Food (25 MCQs)