Part 8: Digestion and Absorption – Miscellaneous & Integration (25 MCQs)

Q1. The average length of the human small intestine is about:

A. 1.5 m
B. 3 m
C. 6 m
D. 10 m

Answer: C

Explanation:

A. Incorrect: 1.5 m is the approximate length of the large intestine.
B. Incorrect: 3 m is too short for small intestine.
C. Correct: Small intestine is about 6 meters long.
D. Incorrect: 10 m is an overestimate.

Q2. Which one of the following is NOT an accessory digestive gland?

A. Liver
B. Pancreas
C. Salivary glands
D. Stomach

Answer: D

Explanation:

A. Incorrect: Liver is accessory.
B. Incorrect: Pancreas is accessory.
C. Incorrect: Salivary glands are accessory.
D. Correct: Stomach is part of the alimentary canal, not accessory.

Q3. The major site of water absorption in the human gut is:

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

Answer: B

Explanation:

A. Incorrect: Stomach absorbs very little water (alcohol, aspirin).
B. Correct: Small intestine absorbs ~90% of water.
C. Incorrect: Large intestine absorbs remaining water.
D. Incorrect: Rectum stores feces.

Q4. Which enzyme is present in saliva?

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

Answer: A

Explanation:

A. Correct: Saliva has salivary amylase (ptyalin).
B. Incorrect: Pepsin is gastric enzyme.
C. Incorrect: Trypsin is pancreatic enzyme.
D. Incorrect: Lipase is gastric/pancreatic.

Q5. Which of the following hormones is secreted when acidic chyme enters duodenum?

A. Gastrin
B. Secretin
C. CCK
D. Ghrelin

Answer: B

Explanation:

A. Incorrect: Gastrin stimulates gastric juice.
B. Correct: Secretin is released by duodenum to neutralize acid.
C. Incorrect: CCK responds to fats.
D. Incorrect: Ghrelin stimulates hunger.

Q6. Which of the following combinations is correct for digestion of proteins?

A. Amylase, lipase, nuclease
B. Pepsin, trypsin, peptidases
C. Lipase, bile salts, amylase
D. Sucrase, lactase, maltase

Answer: B

Explanation:

A. Incorrect: Enzymes for carbs, fats, nucleic acids.
B. Correct: Protein digestion involves pepsin (stomach), trypsin (pancreas), peptidases (intestine).
C. Incorrect: Fat digestion.
D. Incorrect: Carbohydrate digestion.

Q7. The pH of gastric juice is approximately:

A. 1.5–2.0
B. 4.5–5.0
C. 6.8–7.0
D. 8.0–8.5

Answer: A

Explanation:

A. Correct: Gastric juice is highly acidic.
B. Incorrect: Too weak for stomach.
C. Incorrect: Near neutral = saliva.
D. Incorrect: Alkaline = bile/pancreatic juice.

Q8. Which enzyme acts in acidic medium?

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

Answer: A

Explanation:

A. Correct: Pepsin works at pH 1.5–2.0.
B. Incorrect: Trypsin acts in alkaline medium.
C. Incorrect: Amylase works in neutral/alkaline medium.
D. Incorrect: Pancreatic lipase requires bile (alkaline).

Q9. Which organ produces bile?

A. Pancreas
B. Stomach
C. Liver
D. Gallbladder

Answer: C

Explanation:

A. Incorrect: Pancreas produces enzymes.
B. Incorrect: Stomach secretes HCl.
C. Correct: Liver produces bile.
D. Incorrect: Gallbladder only stores bile.

Q10. Which type of teeth are absent in newborn babies?

A. Incisors
B. Canines
C. Molars
D. Premolars

Answer: C

Explanation:

A. Incorrect: Incisors appear first.
B. Incorrect: Canines appear later.
C. Correct: Molars are absent in milk teeth.
D. Incorrect: Premolars are also absent but first molars are key.

Q11. Which vitamin requires intrinsic factor for absorption?

A. Vitamin A
B. Vitamin B12
C. Vitamin C
D. Vitamin D

Answer: B

Explanation:

A. Incorrect: Vitamin A absorbed with fats.
B. Correct: Vitamin B12 needs intrinsic factor from stomach.
C. Incorrect: Vitamin C absorbed directly.
D. Incorrect: Vitamin D absorbed with fats.

Q12. The brush border refers to:

A. Cilia in respiratory tract
B. Microvilli of intestinal mucosa
C. Tongue papillae
D. Hair of villi

Answer: B

Explanation:

A. Incorrect: Cilia line respiratory tract.
B. Correct: Microvilli on enterocytes form brush border for absorption.
C. Incorrect: Tongue papillae aid taste.
D. Incorrect: Villi don’t have hair.

Q13. Which enzyme digests nucleic acids?

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

Answer: A

Explanation:

A. Correct: Nuclease hydrolyzes DNA/RNA.
B. Incorrect: Lipase digests fats.
C. Incorrect: Amylase digests starch.
D. Incorrect: Pepsin digests proteins.

Q14. Which nutrient is digested in the stomach?

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

Answer: B

Explanation:

A. Incorrect: No amylase in gastric juice.
B. Correct: Proteins are digested by pepsin.
C. Incorrect: Fat digestion is minimal.
D. Incorrect: Nucleic acids digested in small intestine.

Q15. Which of the following structures prevents regurgitation of food from stomach to esophagus?

A. Epiglottis
B. Pyloric sphincter
C. Gastroesophageal sphincter
D. Ileocecal valve

Answer: C

Explanation:

A. Incorrect: Epiglottis prevents entry into trachea.
B. Incorrect: Pyloric sphincter controls passage to duodenum.
C. Correct: Gastroesophageal sphincter prevents reflux.
D. Incorrect: Ileocecal valve is between ileum and caecum.

Q16. Which enzyme hydrolyzes sucrose?

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

Answer: A

Explanation:

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

Q17. The pH of pancreatic juice is:

A. 2.0
B. 5.5
C. 7.5–8.0
D. 9.0

Answer: C

Explanation:

A. Incorrect: Too acidic.
B. Incorrect: Still acidic.
C. Correct: Pancreatic juice is alkaline due to bicarbonates.
D. Incorrect: 9.0 is extreme.

Q18. Which of the following is a proteolytic enzyme?

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

Answer: A

Explanation:

A. Correct: Pepsin hydrolyzes proteins.
B. Incorrect: Amylase → starch.
C. Incorrect: Lipase → fats.
D. Incorrect: Sucrase → sucrose.

Q19. Which nutrient is absorbed in large intestine?

A. Amino acids
B. Vitamin K
C. Glucose
D. Fatty acids

Answer: B

Explanation:

A. Incorrect: Amino acids absorbed in small intestine.
B. Correct: Vitamin K (and some B-complex vitamins) are absorbed in large intestine.
C. Incorrect: Glucose absorbed in small intestine.
D. Incorrect: Fats absorbed in small intestine.

Q20. Which enzyme is secreted in inactive form?

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

Answer: A

Explanation:

A. Correct: Pepsinogen → pepsin in acidic medium.
B. Incorrect: Amylase secreted active.
C. Incorrect: Lipase active.
D. Incorrect: Maltase active.

Q21. Which organ regulates blood glucose by glycogen storage and release?

A. Kidney
B. Liver
C. Pancreas
D. Stomach

Answer: B

Explanation:

A. Incorrect: Kidneys filter waste.
B. Correct: Liver stores glycogen and releases glucose.
C. Incorrect: Pancreas regulates with insulin/glucagon but does not store glycogen.
D. Incorrect: Stomach has no such role.

Q22. Which of the following enzymes is present in infants but absent in adults?

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

Answer: A

Explanation:

A. Correct: Rennin coagulates milk protein in infants.
B. Incorrect: Amylase is present in both.
C. Incorrect: Trypsin is present in both.
D. Incorrect: Lipase is present in both.

Q23. The hormone that stimulates release of insulin is:

A. Gastrin
B. Secretin
C. GIP (gastric inhibitory peptide)
D. CCK

Answer: C

Explanation:

A. Incorrect: Gastrin regulates gastric juice.
B. Incorrect: Secretin stimulates pancreas (bicarbonate).
C. Correct: GIP stimulates insulin release.
D. Incorrect: CCK stimulates pancreas and gallbladder.

Q24. Which one is called the “second brain” of the human body?

A. Pancreas
B. Enteric nervous system
C. Liver
D. Hypothalamus

Answer: B

Explanation:

A. Incorrect: Pancreas secretes enzymes/hormones.
B. Correct: Enteric nervous system autonomously regulates digestion.
C. Incorrect: Liver is metabolic hub.
D. Incorrect: Hypothalamus is in CNS.

Q25. Which of the following nutrients is digested by enzymes secreted in saliva, stomach, and intestine?

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

Answer: B

Explanation:

A. Incorrect: Carbohydrate digestion starts in mouth and small intestine only.
B. Correct: Proteins are digested in stomach (pepsin), pancreas (trypsin), intestine (peptidases).
C. Incorrect: Fat digestion mainly in small intestine.
D. Incorrect: Nucleic acids only in small intestine.

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Part 8: Digestion and Absorption – Miscellaneous & Integration (25 MCQs)