MCQ on Digestive System

🟢 Easy Level (1–20)

1. Where does digestion begin in the human body?
   A) Stomach
   B) Mouth ✅
   C) Small intestine
   D) Esophagus
   Explanation: Mechanical and enzymatic digestion (via salivary amylase) starts in the mouth.
2. Which enzyme breaks down starch?
   A) Pepsin
   B) Lipase
   C) Amylase ✅
   D) Trypsin
   Explanation: Amylase breaks down starch into sugars.
3. What is the main function of the small intestine?
   A) Absorption of nutrients ✅
   B) Water absorption
   C) Protein digestion
   D) Storage of food
   Explanation: Most digestion and absorption occur in the small intestine.
4. Which organ produces bile?
   A) Stomach
   B) Liver ✅
   C) Gallbladder
   D) Pancreas
   Explanation: The liver produces bile; the gallbladder stores it.
5. Where is bile stored?
   A) Pancreas
   B) Small intestine
   C) Gallbladder ✅
   D) Liver
   Explanation: The gallbladder stores and concentrates bile.
6. Which part of the digestive tract absorbs water?
   A) Small intestine
   B) Large intestine ✅
   C) Stomach
   D) Esophagus
   Explanation: The large intestine absorbs water and forms feces.
7. Pepsin digests:
   A) Carbohydrates
   B) Proteins ✅
   C) Lipids
   D) Nucleic acids
   Explanation: Pepsin, active in the stomach, breaks proteins into peptides.
8. The rhythmic contractions that move food through the digestive tract are called:
   A) Segmentation
   B) Peristalsis ✅
   C) Churning
   D) Egestion
   Explanation: Peristalsis propels food along the gastrointestinal tract.
9. The organ that connects the mouth to the stomach is the:
   A) Trachea
   B) Esophagus ✅
   C) Duodenum
   D) Colon
   Explanation: The esophagus carries food from the mouth to the stomach.
10. What is the pH of the stomach?
    A) Neutral
    B) Basic
    C) Acidic ✅
    D) Slightly alkaline
    Explanation: The stomach’s acidic pH (1.5–3.5) aids protein digestion.
11. Which macronutrient begins digestion in the mouth?
    A) Protein
    B) Fat
    C) Carbohydrate ✅
    D) Fiber
    Explanation: Salivary amylase starts breaking down starch.
12. Which vitamin is produced by gut bacteria?
    A) Vitamin A
    B) Vitamin B12
    C) Vitamin C
    D) Vitamin K ✅
    Explanation: Gut flora synthesizes vitamin K.
13. The pancreas secretes:
    A) Bile
    B) Hydrochloric acid
    C) Digestive enzymes ✅
    D) Mucus
    Explanation: Pancreas releases enzymes like lipase, amylase, and trypsin.
14. Which structure prevents food from entering the windpipe?
    A) Epiglottis ✅
    B) Uvula
    C) Tongue
    D) Pharynx
    Explanation: The epiglottis covers the larynx during swallowing.
15. The innermost layer of the digestive tract is the:
    A) Serosa
    B) Muscularis
    C) Mucosa ✅
    D) Submucosa
    Explanation: The mucosa is in direct contact with food and contains glands.
16. The part of the small intestine that receives bile and pancreatic juice is the:
    A) Jejunum
    B) Ileum
    C) Duodenum ✅
    D) Colon
    Explanation: The duodenum is the site of major chemical digestion.
17. Which of these organs is NOT part of the digestive system?
    A) Liver
    B) Gallbladder
    C) Heart ✅
    D) Pancreas
    Explanation: The heart is part of the circulatory system.
18. Which nutrient is digested by lipase?
    A) Carbohydrates
    B) Proteins
    C) Fats ✅
    D) Vitamins
    Explanation: Lipase breaks down lipids into fatty acids and glycerol.
19. Which digestive enzyme is secreted in an inactive form?
    A) Amylase
    B) Pepsinogen ✅
    C) Maltase
    D) Lactase
    Explanation: Pepsinogen activates to pepsin in acidic pH.
20. Where does most protein digestion occur?
    A) Mouth
    B) Esophagus
    C) Stomach ✅
    D) Colon
    Explanation: Pepsin in the stomach begins protein breakdown.

🟡 Moderate Level (21–40)

21. Which organ absorbs most nutrients?
    A) Stomach
    B) Small intestine ✅
    C) Large intestine
    D) Esophagus
    Explanation: Villi and microvilli increase absorption in the small intestine.
22. Which hormone stimulates the release of gastric juice?
    A) Secretin
    B) Gastrin ✅
    C) Cholecystokinin
    D) Insulin
    Explanation: Gastrin is released in response to food in the stomach.
23. What does cholecystokinin (CCK) stimulate?
    A) Bile production
    B) Insulin release
    C) Gallbladder contraction ✅
    D) Gastric acid secretion
    Explanation: CCK stimulates bile release from the gallbladder.
24. Lactose intolerance is caused by deficiency of:
    A) Amylase
    B) Lipase
    C) Lactase ✅
    D) Sucrase
    Explanation: Lactase breaks down lactose; its deficiency causes intolerance.
25. Which is a brush-border enzyme?
    A) Pepsin
    B) Sucrase ✅
    C) Trypsin
    D) Lipase
    Explanation: Sucrase is located on the microvilli of intestinal cells.
26. Which component of bile helps emulsify fats?
    A) Bile pigments
    B) Cholesterol
    C) Bile salts ✅
    D) Enzymes
    Explanation: Bile salts break fat into smaller droplets for digestion.
27. Which region of the stomach connects to the esophagus?
    A) Pylorus
    B) Fundus
    C) Cardia ✅
    D) Body
    Explanation: The cardia receives food from the esophagus.
28. What is the role of intrinsic factor?
    A) Emulsify fats
    B) Digest proteins
    C) Absorb vitamin B12 ✅
    D) Neutralize acid
    Explanation: Intrinsic factor is needed for B12 absorption in the ileum.
29. Enterokinase activates:
    A) Pepsinogen
    B) Trypsinogen ✅
    C) Amylase
    D) Lipase
    Explanation: Enterokinase converts trypsinogen to active trypsin.
30. Which nutrient is absorbed in the stomach?
    A) Proteins
    B) Alcohol ✅
    C) Fats
    D) Carbohydrates
    Explanation: The stomach absorbs alcohol and a few other substances.
31. The large intestine is primarily responsible for:
    A) Digesting starch
    B) Absorbing nutrients
    C) Absorbing water ✅
    D) Breaking down proteins
    Explanation: Water and electrolytes are absorbed in the colon.
32. Which part of the alimentary canal has no digestive function?
    A) Mouth
    B) Esophagus ✅
    C) Small intestine
    D) Stomach
    Explanation: The esophagus is a conduit, not involved in digestion.
33. Which organ secretes both endocrine and exocrine substances?
    A) Liver
    B) Gallbladder
    C) Pancreas ✅
    D) Stomach
    Explanation: The pancreas secretes digestive enzymes and hormones.
34. Trypsin digests:
    A) Carbohydrates
    B) Proteins ✅
    C) Fats
    D) Nucleic acids
    Explanation: Trypsin breaks down proteins in the small intestine.
35. Which of the following is a zymogen?
    A) Lipase
    B) Trypsinogen ✅
    C) Amylase
    D) Maltase
    Explanation: Zymogens are inactive enzyme precursors like trypsinogen.
36. The main function of villi is to:
    A) Digest food
    B) Transport nutrients
    C) Increase surface area for absorption ✅
    D) Secrete enzymes
    Explanation: Villi maximize nutrient absorption.
37. Which vitamin enhances calcium absorption?
    A) Vitamin C
    B) Vitamin D ✅
    C) Vitamin B12
    D) Vitamin K
    Explanation: Vitamin D promotes intestinal calcium absorption.
38. Which part of the small intestine absorbs vitamin B12?
    A) Duodenum
    B) Jejunum
    C) Ileum ✅
    D) Colon
    Explanation: The ileum is the primary site for B12 absorption.
39. Which is the longest part of the small intestine?
    A) Duodenum
    B) Ileum ✅
    C) Jejunum
    D) Cecum
    Explanation: The ileum is the longest section of the small intestine.
40. The movement of food from stomach to intestine is regulated by:
    A) Cardiac sphincter
    B) Pyloric sphincter ✅
    C) Ileocecal valve
    D) Esophageal valve
    Explanation: The pyloric sphincter controls gastric emptying.

🔴 Hard Level (41–50)

41. Which hormone inhibits gastric emptying?
    A) Gastrin
    B) Secretin
    C) Cholecystokinin ✅
    D) Insulin
    Explanation: CCK slows gastric emptying to allow fat digestion.
42. Pancreatic zymogens are activated by:
    A) HCl
    B) Enteropeptidase ✅
    C) Gastrin
    D) Secretin
    Explanation: Enteropeptidase (enterokinase) activates trypsinogen.
43. What is the role of Brunner’s glands?
    A) Secrete bile
    B) Secrete mucus in duodenum ✅
    C) Absorb nutrients
    D) Digest proteins
    Explanation: These glands protect the duodenal lining with alkaline mucus.
44. The Kupffer cells in the liver are responsible for:
    A) Storing bile
    B) Fat digestion
    C) Phagocytosis ✅
    D) Vitamin storage
    Explanation: Kupffer cells remove pathogens and debris.
45. Which component of bile gives it its color?
    A) Cholesterol
    B) Bile salts
    C) Bilirubin ✅
    D) Enzymes
    Explanation: Bilirubin (a hemoglobin breakdown product) gives bile its color.
46. Which part of the GI tract is retroperitoneal?
    A) Esophagus
    B) Duodenum ✅
    C) Stomach
    D) Ileum
    Explanation: The duodenum (except the first part) is retroperitoneal.
47. Paneth cells secrete:
    A) Mucus
    B) Digestive enzymes
    C) Antimicrobial peptides ✅
    D) Hormones
    Explanation: Paneth cells release lysozyme and defensins.
48. Which enzyme digests nucleic acids?
    A) Lipase
    B) Amylase
    C) Nuclease ✅
    D) Pepsin
    Explanation: Nucleases break DNA and RNA into nucleotides.
49. What structure increases absorption in the small intestine microscopically?
    A) Villi
    B) Rugae
    C) Microvilli ✅
    D) Haustra
    Explanation: Microvilli form the brush border and aid absorption.
50. A condition with inflamed intestinal diverticula is called:
    A) Ulcerative colitis
    B) Crohn’s disease
    C) Diverticulitis ✅
    D) Irritable bowel syndrome
    Explanation: Diverticulitis involves infection/inflammation of pouches in the colon wall.