Chapter 16: Digestion and Absorption – MCQs
Digestion & Absorption – MCQs Part 1 — Q1–Q25
Q1. Which cells of the stomach secrete hydrochloric acid (HCl)?
a) Chief cells
b) Parietal (oxyntic) cells
c) Mucous neck cells
d) G cells
Answer: b) Parietal (oxyntic) cells
Explanations:
- a) Chief cells — secrete pepsinogen (inactive enzyme), not HCl.
- b) Parietal cells — correct; they secrete HCl and intrinsic factor.
- c) Mucous neck cells — secrete mucus and some bicarbonate to protect mucosa, not HCl.
- d) G cells — secrete gastrin (hormone) which stimulates HCl release but do not secrete HCl themselves.
Q2. Pepsin is secreted in active form from the stomach. True or false?
a) True
b) False
c) Only after food intake
d) Only in infants
Answer: b) False
Explanations:
- a) True — incorrect: pepsin is secreted as pepsinogen (inactive).
- b) False — correct; pepsinogen (from chief cells) is activated to pepsin by low pH (HCl) or by existing pepsin.
- c) Only after food intake — not strictly; secretion increases with food but the form is still zymogen.
- d) Only in infants — wrong; pepsin/pepsinogen present at all ages.
Q3. Which substance emulsifies dietary fats, aiding lipase action?
a) Pancreatic lipase
b) Bile salts
c) Trypsin
d) Secretin
Answer: b) Bile salts
Explanations:
- a) Pancreatic lipase — enzyme that hydrolyzes triglycerides but needs emulsification to be efficient.
- b) Bile salts — correct; amphipathic molecules that emulsify fat droplets increasing surface area.
- c) Trypsin — protease for proteins, not emulsifier.
- d) Secretin — hormone stimulating bicarbonate secretion; not an emulsifier.
Q4. Activation of trypsinogen (pancreatic zymogen) in the small intestine is primarily by:
a) Enterokinase (enteropeptidase) on brush border
b) HCl in stomach
c) Pancreatic amylase
d) Bile salts
Answer: a) Enterokinase (enteropeptidase) on brush border
Explanations:
- a) Enterokinase (enteropeptidase) — correct; converts trypsinogen → trypsin which then activates other zymogens.
- b) HCl in stomach — activates pepsinogen, not pancreatic zymogens.
- c) Pancreatic amylase — digests starch; not involved in protease activation.
- d) Bile salts — aid lipid digestion/emulsification but not zymogen activation.
Q5. The primary site for absorption of most nutrients (carbohydrates, proteins, lipids) is the:
a) Stomach
b) Duodenum and jejunum (small intestine)
c) Ileum only
d) Large intestine (colon)
Answer: b) Duodenum and jejunum (small intestine)
Explanations:
- a) Stomach — minimal absorption (some drugs, alcohol).
- b) Duodenum & jejunum — correct; main regions for digestion and absorption of nutrients.
- c) Ileum — important for bile salt and B12 absorption, but not the major site for all nutrients.
- d) Large intestine — mainly absorbs water, electrolytes; limited nutrient absorption.
Q6. Intrinsic factor is essential for absorption of:
a) Vitamin C
b) Vitamin B12 (cobalamin)
c) Iron
d) Calcium
Answer: b) Vitamin B12 (cobalamin)
Explanations:
- a) Vitamin C — absorbed without intrinsic factor.
- b) Vitamin B12 — correct; intrinsic factor (from parietal cells) binds B12 so it can be absorbed in the terminal ileum.
- c) Iron — absorbed in duodenum often with help of heme transporters and ferric reductase, not intrinsic factor.
- d) Calcium — absorbed via vitamin D–dependent mechanisms, not intrinsic factor.
Q7. Which transporter mediates active uptake of glucose from the intestinal lumen into enterocytes?
a) GLUT2 (facilitated diffusion) at apical membrane
b) SGLT1 (sodium-glucose cotransporter) at apical membrane
c) GLUT5 (fructose transporter) at basolateral membrane
d) Na⁺/K⁺ ATPase directly transports glucose
Answer: b) SGLT1 (sodium-glucose cotransporter) at apical membrane
Explanations:
- a) GLUT2 — facilitates glucose transport, but mainly on basolateral (and sometimes apical after high sugar load); not primary active apical uptake.
- b) SGLT1 — correct; uses sodium gradient to actively cotransport glucose/galactose into enterocytes.
- c) GLUT5 — transports fructose (facilitated diffusion) on apical side, not glucose.
- d) Na⁺/K⁺ ATPase — maintains sodium gradient but does not directly transport glucose.
Q8. Fructose absorption across the apical membrane of enterocytes occurs primarily via:
a) SGLT1 (Na⁺-dependent)
b) GLUT5 (facilitated diffusion)
c) GLUT2 active transport
d) Endocytosis
Answer: b) GLUT5 (facilitated diffusion)
Explanations:
- a) SGLT1 — transports glucose/galactose, not fructose.
- b) GLUT5 — correct; specific facilitated transporter for fructose on apical surface.
- c) GLUT2 — usually on basolateral side for exit into blood (can appear apically under high glucose).
- d) Endocytosis — not the normal route for monosaccharide uptake.
Q9. Which of the following enzymes is a brush-border (membrane) enzyme of the small intestine?
a) Salivary amylase
b) Pancreatic trypsin
c) Lactase (β-galactosidase)
d) Lipoprotein lipase
Answer: c) Lactase (β-galactosidase)
Explanations:
- a) Salivary amylase — produced in mouth, not brush border.
- b) Pancreatic trypsin — pancreatic, activated in lumen; not membrane-bound.
- c) Lactase — correct; located on enterocyte brush border; digests lactose → glucose + galactose.
- d) Lipoprotein lipase — endothelial enzyme acting on circulating chylomicrons/VLDL, not brush border.
Q10. Which lipoprotein carries dietary (exogenous) triglycerides from enterocytes into lymph?
a) VLDL
b) LDL
c) Chylomicrons
d) HDL
Answer: c) Chylomicrons
Explanations:
- a) VLDL — primarily liver-derived endogenous triglyceride carriers.
- b) LDL — cholesterol-rich remnants from VLDL; not main dietary TG carriers.
- c) Chylomicrons — correct; large lipoproteins formed in enterocytes that transport dietary TG via lymph (lacteals) to bloodstream.
- d) HDL — involved in reverse cholesterol transport.
Q11. Bile salts are reabsorbed in the intestine by:
a) Simple diffusion in duodenum
b) Active transport in the terminal ileum (enterohepatic circulation)
c) Absorbed only in colon
d) Not reabsorbed — excreted in feces
Answer: b) Active transport in the terminal ileum (enterohepatic circulation)
Explanations:
- a) Simple diffusion in duodenum — incorrect; bile salts are largely ionized and require transport.
- b) Terminal ileum active transport — correct; bile salts are efficiently returned to liver via portal blood (enterohepatic recirculation).
- c) Colon — minor reabsorption of some bile acids but primary site is ileum.
- d) Not reabsorbed — false; most bile salts are recycled.
Q12. Secretin, released by S cells in the duodenum, primarily stimulates:
a) Pancreatic enzyme secretion
b) Pancreatic bicarbonate secretion to neutralize acid
c) Gallbladder contraction
d) Gastric motility
Answer: b) Pancreatic bicarbonate secretion to neutralize acid
Explanations:
- a) Pancreatic enzyme secretion — mainly stimulated by CCK, not secretin.
- b) Secretin → correct; stimulates pancreatic duct cells to secrete HCO₃⁻, neutralizing gastric acid in duodenum.
- c) Gallbladder contraction — chiefly by CCK.
- d) Gastric motility — secretin generally inhibits gastric acid secretion/motility.
Q13. Cholecystokinin (CCK) primarily does which of the following?
a) Stimulates gastric acid secretion only
b) Causes gallbladder contraction and pancreatic enzyme secretion
c) Stimulates bicarbonate release from pancreas only
d) Enhances intestinal absorption of iron
Answer: b) Causes gallbladder contraction and pancreatic enzyme secretion
Explanations:
- a) Stimulates gastric acid — not main function; CCK can slow gastric emptying.
- b) Correct; fatty acids and amino acids in lumen trigger CCK release → gallbladder contraction (bile) + pancreatic enzyme secretion (lipases, proteases).
- c) Bicarbonate release — mainly secretin.
- d) Iron absorption — regulated by other mechanisms (hepcidin, duodenal factors).
Q14. Dietary protein digestion begins in the:
a) Mouth (salivary proteases)
b) Stomach (pepsin)
c) Duodenum only (pancreatic proteases)
d) Ileum
Answer: b) Stomach (pepsin)
Explanations:
- a) Mouth — no significant protease activity in saliva (except minor lingual lipase for fats).
- b) Stomach — correct; pepsin (active form) initiates protein digestion by cleaving peptide bonds.
- c) Duodenum — major site for further proteolysis (trypsin, chymotrypsin) but digestion begins in stomach.
- d) Ileum — mostly absorption of amino acids/peptides, not initial digestion.
Q15. Dipeptides and tripeptides are absorbed into enterocytes mainly via:
a) SGLT1 cotransport
b) H⁺-dependent peptide transporters (e.g., PepT1)
c) GLUT transporters
d) Simple diffusion
Answer: b) H⁺-dependent peptide transporters (e.g., PepT1)
Explanations:
- a) SGLT1 — transports glucose/galactose, not peptides.
- b) PepT1 — correct; H⁺-coupled transporter that absorbs di- and tri-peptides efficiently.
- c) GLUTs — sugar transporters (fructose, glucose), not peptides.
- d) Simple diffusion — peptides are charged/polar; need transporters.
Q16. Vitamin B12 absorption requires which of the following sequentially?
a) Intrinsic factor (IF) binding in stomach → absorption in terminal ileum
b) HCl only in stomach → absorption in duodenum
c) Pancreatic lipase → micelle formation
d) Bile acids → absorption in jejunum
Answer: a) Intrinsic factor (IF) binding in stomach → absorption in terminal ileum
Explanations:
- a) Correct; B12 binds R-proteins then IF, complex absorbed in ileum.
- b) HCl helps release B12 from food but IF and ileal absorption are essential.
- c) Pancreatic lipase/micelles relate to lipids, not B12.
- d) Bile acids/micelles — lipid absorption mainly in jejunum; B12 absorption is ileal and IF-dependent.
Q17. Which of the following statements about pancreatic secretions is correct?
a) Pancreatic juice is isotonic with plasma at all flow rates and high in bicarbonate at high flow rates
b) Pancreatic juice is hypotonic and low in bicarbonate at all times
c) Pancreatic juice ionic composition does not change with flow rate
d) Pancreatic acinar cells secrete mostly bicarbonate
Answer: a) Pancreatic juice is isotonic with plasma at all flow rates and high in bicarbonate at high flow rates
Explanations:
- a) Correct; pancreatic fluid is isotonic; at high flow rates (stimulated by secretin) bicarbonate concentration increases, chloride falls.
- b) False — not hypotonic.
- c) False — ionic composition varies with flow: HCO₃⁻ increases with flow.
- d) Acinar cells produce enzyme-rich secretion; ductal cells secrete bicarbonate.
Q18. Absorption of calcium in the intestine is enhanced by:
a) Vitamin D (1,25-(OH)₂D₃)
b) Intrinsic factor
c) Bile salts only
d) Secretin
Answer: a) Vitamin D (1,25-(OH)₂D₃)
Explanations:
- a) Vitamin D — correct; stimulates synthesis of calbindin and increases active Ca²⁺ transport in intestine.
- b) Intrinsic factor — for B12, not Ca.
- c) Bile salts — aid fat absorption; minimal direct effect on Ca²⁺.
- d) Secretin — stimulates bicarbonate, not Ca absorption.
Q19. Which statement best describes the movement of chyme from stomach to small intestine?
a) Rapid continuous emptying of all stomach contents into jejunum
b) Regulated gastric emptying: pyloric sphincter allows small portions (chyme) into duodenum; slowed by fats/acid/hypertonicity
c) Pyloric sphincter completely closed during digestion
d) Duodenum actively forces contents back into stomach during digestion
Answer: b) Regulated gastric emptying: pyloric sphincter allows small portions (chyme) into duodenum; slowed by fats/acid/hypertonicity
Explanations:
- a) Not accurate — emptying is regulated, not wholesale.
- b) Correct; fat, acidic pH, hypertonic contents, and CCK/secretin slow gastric emptying.
- c) False — pylorus opens intermittently to allow controlled emptying.
- d) Retroperistalsis can occur but duodenum generally does not forcibly push back continuously.
Q20. Which of the following vitamins is fat-soluble and requires micelle formation for absorption?
a) Vitamin C
b) Vitamin B1 (thiamine)
c) Vitamin A
d) Vitamin B12
Answer: c) Vitamin A
Explanations:
- a) Vitamin C — water-soluble, absorbed without micelles.
- b) Thiamine — water-soluble.
- c) Vitamin A — correct; fat-soluble vitamins (A, D, E, K) require bile salts/micelles for absorption.
- d) B12 — water-soluble but IF-dependent, not micelle-dependent.
Q21. The main mechanism for water absorption in the small intestine is:
a) Active transport of water via aquaporins only
b) Osmosis following solute (e.g., Na⁺, glucose, amino acids) absorption
c) Pinocytosis of water molecules
d) Colon microflora fermentation
Answer: b) Osmosis following solute (e.g., Na⁺, glucose, amino acids) absorption
Explanations:
- a) Aquaporins facilitate water movement but osmotic gradient is the driving force.
- b) Correct; solute transport creates osmotic gradients that drive water absorption.
- c) Pinocytosis — not principal mechanism for bulk water uptake.
- d) Colon bacteria ferment fibers producing short-chain fatty acids—affects colonic absorption but not main small intestinal water uptake mechanism.
Q22. Which of the following best describes the role of lacteals in the small intestinal villus?
a) Absorb monosaccharides into portal blood
b) Transport absorbed lipids (as chylomicrons) into lymphatic circulation
c) Secrete digestive enzymes
d) Store bile salts
Answer: b) Transport absorbed lipids (as chylomicrons) into lymphatic circulation
Explanations:
- a) Monosaccharides enter capillaries (portal blood), not lacteals.
- b) Correct; lacteals are central lymph vessels that take up chylomicrons and return lipids via lymph.
- c) Enterocytes secrete enzymes; lacteals do not.
- d) Bile salts stored in gallbladder, not lacteals.
Q23. Which of the following is NOT a function of saliva?
a) Begins starch digestion (salivary amylase)
b) Lubricates food and aids swallowing
c) Activates pepsinogen to pepsin in the mouth
d) Provides antimicrobial action (lysozyme, IgA)
Answer: c) Activates pepsinogen to pepsin in the mouth
Explanations:
- a) True — salivary amylase (ptyalin) starts starch digestion.
- b) True — mucus in saliva lubricates bolus formation.
- c) Correct (not a function); pepsin activation requires low pH in stomach — not saliva.
- d) True — saliva contains antimicrobial components.
Q24. Which condition results when the lower esophageal sphincter fails to close properly, allowing gastric acid to reflux?
a) Gastritis
b) Peptic ulcer disease
c) Gastroesophageal reflux disease (GERD) / heartburn
d) Achalasia
Answer: c) Gastroesophageal reflux disease (GERD) / heartburn
Explanations:
- a) Gastritis — inflammation of stomach lining; can be related but reflux specifically causes GERD symptoms.
- b) Peptic ulcer disease — mucosal ulceration; not the immediate consequence of LES incompetence.
- c) Correct; LES dysfunction leads to acid reflux and heartburn (GERD).
- d) Achalasia — failure of LES to relax, causing dysphagia; opposite of incompetent LES.
Q25. The major end-products of carbohydrate digestion that are absorbed by the small intestine are:
a) Disaccharides only
b) Monosaccharides (glucose, galactose, fructose)
c) Polysaccharides only
d) Amino acids
Answer: b) Monosaccharides (glucose, galactose, fructose)
Explanations:
- a) Disaccharides — must be broken down by brush-border enzymes into monosaccharides before absorption.
- b) Correct; final absorbable products are monosaccharides: glucose, galactose (via SGLT1), and fructose (via GLUT5).
- c) Polysaccharides — large polymers, digested down to monosaccharides.
- d) Amino acids — products of protein digestion, not carbohydrates.
Part 2: Human Physiology – Digestion and Absorption (Q26–Q50)
Q26. Which enzyme is responsible for the digestion of protein in the stomach?
a) Pepsin
b) Trypsin
c) Lipase
d) Amylase
✅ Answer: a) Pepsin
- Pepsin is the main proteolytic enzyme in the stomach, breaking proteins into peptides.
- Trypsin acts in the small intestine, not the stomach.
- Lipase digests fats.
- Amylase digests carbohydrates.
Q27. The brush border cells of the small intestine have:
a) Microvilli
b) Cilia
c) Flagella
d) None
✅ Answer: a) Microvilli
- Microvilli increase the absorptive surface area of the small intestine.
- Cilia and flagella are for motility, not absorption.
Q28. Which part of the digestive system mainly absorbs water and salts?
a) Stomach
b) Small intestine
c) Large intestine
d) Esophagus
✅ Answer: c) Large intestine
- The large intestine absorbs most water and electrolytes.
- The small intestine mainly absorbs nutrients.
- The stomach and esophagus are not for water absorption.
Q29. Bile salts help in digestion of:
a) Proteins
b) Fats
c) Carbohydrates
d) Nucleic acids
✅ Answer: b) Fats
- Bile salts emulsify fats, aiding lipase activity.
- Proteins and carbohydrates do not require bile salts.
Q30. Which vitamin requires intrinsic factor for absorption?
a) Vitamin A
b) Vitamin B12
c) Vitamin D
d) Vitamin K
✅ Answer: b) Vitamin B12
- Vitamin B12 absorption in the ileum requires intrinsic factor secreted by the stomach.
Q31. Which enzyme digests milk protein casein in infants?
a) Rennin
b) Trypsin
c) Pepsin
d) Amylase
✅ Answer: a) Rennin
- Rennin (chymosin) coagulates casein in infants.
- Pepsin also acts but rennin is more specific.
Q32. Which is the first enzyme to act on food during digestion?
a) Salivary amylase
b) Pepsin
c) Lipase
d) Trypsin
✅ Answer: a) Salivary amylase
- Salivary amylase starts digestion of starch in the mouth.
- Others act later in the stomach or intestine.
Q33. Absorption of amino acids occurs mainly in:
a) Stomach
b) Small intestine
c) Large intestine
d) Mouth
✅ Answer: b) Small intestine
- Small intestine (jejunum and ileum) absorbs amino acids.
- The stomach only digests proteins into peptides, not absorption.
Q34. Which organ secretes digestive enzymes and also functions as an endocrine gland?
a) Liver
b) Pancreas
c) Gallbladder
d) Large intestine
✅ Answer: b) Pancreas
- Pancreas has exocrine (digestive enzymes) and endocrine (insulin, glucagon) roles.
Q35. The digestion of nucleic acids occurs in:
a) Stomach
b) Small intestine
c) Large intestine
d) Liver
✅ Answer: b) Small intestine
- Nucleases (DNase and RNase) act in the small intestine.
Q36. Which enzyme is NOT found in the pancreatic juice?
a) Lipase
b) Trypsin
c) Amylase
d) Pepsin
✅ Answer: d) Pepsin
- Pepsin is secreted by the stomach, not pancreas.
Q37. Which of the following is a proteolytic enzyme?
a) Amylase
b) Maltase
c) Pepsin
d) Sucrase
✅ Answer: c) Pepsin
- Pepsin digests proteins.
- Others digest carbohydrates.
Q38. Which of the following is NOT a function of bile?
a) Emulsification of fats
b) Neutralization of chyme
c) Digestion of proteins
d) Absorption of fat-soluble vitamins
✅ Answer: c) Digestion of proteins
- Bile emulsifies fats, neutralizes acidic chyme, and aids vitamin absorption, but does not digest proteins.
Q39. Absorption of glucose occurs through:
a) Simple diffusion
b) Facilitated diffusion
c) Active transport
d) Osmosis
✅ Answer: c) Active transport
- Glucose absorption is an active transport process, requiring ATP.
Q40. Which part of the digestive tract contains villi?
a) Stomach
b) Small intestine
c) Large intestine
d) Rectum
✅ Answer: b) Small intestine
- Villi and microvilli increase surface area for absorption.
Q41. The secretion of gastric juice is regulated by which hormone?
a) Gastrin
b) Secretin
c) Cholecystokinin
d) Insulin
✅ Answer: a) Gastrin
- Gastrin stimulates gastric juice secretion.
- Secretin and CCK act on pancreas and bile release.
Q42. Which enzyme converts trypsinogen to trypsin?
a) Enterokinase
b) Pepsin
c) Lipase
d) Amylase
✅ Answer: a) Enterokinase
- Enterokinase (in the small intestine) activates trypsinogen to trypsin.
Q43. Which structure prevents entry of food into the trachea during swallowing?
a) Epiglottis
b) Glottis
c) Uvula
d) Pharynx
✅ Answer: a) Epiglottis
- Epiglottis closes the trachea during swallowing.
Q44. The pH of the stomach is generally:
a) 2
b) 5
c) 7
d) 9
✅ Answer: a) 2
- Gastric HCl makes stomach contents highly acidic, pH ~2.
Q45. Which part of the alimentary canal has crypts of Lieberkühn?
a) Stomach
b) Small intestine
c) Large intestine
d) Esophagus
✅ Answer: b) Small intestine
- Crypts of Lieberkühn secrete intestinal juice in small intestine.
Q46. Which enzyme converts proteins into peptides in the stomach?
a) Pepsin
b) Trypsin
c) Rennin
d) Lipase
✅ Answer: a) Pepsin
- Pepsin digests proteins into smaller peptides.
Q47. Which part of the digestive system is involved in maximum absorption of nutrients?
a) Duodenum
b) Jejunum
c) Ileum
d) Colon
✅ Answer: b) Jejunum
- The jejunum is the primary site of maximum absorption of nutrients.
Q48. Which enzyme hydrolyzes lactose?
a) Maltase
b) Sucrase
c) Lactase
d) Lipase
✅ Answer: c) Lactase
- Lactase breaks down lactose into glucose and galactose.
Q49. Which structure stores bile?
a) Liver
b) Pancreas
c) Gallbladder
d) Duodenum
✅ Answer: c) Gallbladder
- Gallbladder stores and releases bile.
Q50. The final products of protein digestion are:
a) Amino acids
b) Peptides
c) Polypeptides
d) Fatty acids
✅ Answer: a) Amino acids
- Proteins are fully digested into amino acids, which are absorbed.
Part 3: Human Physiology – Digestion and Absorption (Q51–Q75)
Q51. The largest gland in the human body is:
a) Pancreas
b) Liver
c) Stomach
d) Gall bladder
Answer: b) Liver
- Explanation: The liver is the largest gland in humans, weighing about 1.2–1.5 kg. It secretes bile which aids in digestion of fats.
Q52. The functional unit of the liver is called:
a) Acinus
b) Lobule
c) Nephron
d) Islet
Answer: b) Lobule
- Explanation: The liver lobule is the structural and functional unit of the liver, consisting of hepatocytes arranged around a central vein.
Q53. Which of the following enzymes is secreted in an inactive form?
a) Pepsin
b) Lipase
c) Trypsin
d) Salivary amylase
Answer: c) Trypsin
- Explanation: Trypsin is secreted as inactive trypsinogen by the pancreas to prevent autodigestion; it is activated in the intestine by enterokinase.
Q54. The hormone secreted by the stomach that stimulates secretion of gastric juice is:
a) Secretin
b) Gastrin
c) Cholecystokinin
d) Enterogastrone
Answer: b) Gastrin
- Explanation: Gastrin stimulates gastric glands to secrete gastric juice containing HCl and pepsinogen.
Q55. Which structure prevents the entry of food into the respiratory tract during swallowing?
a) Uvula
b) Glottis
c) Epiglottis
d) Pharynx
Answer: c) Epiglottis
- Explanation: The epiglottis is a flap-like structure that closes the glottis while swallowing, preventing food from entering the trachea.
Q56. The process of emulsification of fats is carried out by:
a) Lipase
b) Pepsin
c) Bile salts
d) Gastrin
Answer: c) Bile salts
- Explanation: Bile salts break down large fat globules into small droplets, increasing the surface area for lipase action.
Q57. Rennin enzyme in infants helps in the digestion of:
a) Protein
b) Fat
c) Carbohydrate
d) Lactose
Answer: a) Protein
- Explanation: Rennin (chymosin) coagulates milk protein casein, making it easier for pepsin to digest in infants.
Q58. Which of the following is NOT secreted by the pancreas?
a) Trypsinogen
b) Amylase
c) Bile
d) Lipase
Answer: c) Bile
- Explanation: Bile is secreted by the liver, not by the pancreas. Pancreas secretes trypsinogen, amylase, and lipase.
Q59. The main site of absorption of water in the digestive system is:
a) Stomach
b) Small intestine
c) Large intestine
d) Rectum
Answer: c) Large intestine
- Explanation: The large intestine mainly absorbs water and electrolytes, forming solid feces.
Q60. Which one of the following is a brush-border enzyme?
a) Pepsin
b) Maltase
c) Lipase
d) Rennin
Answer: b) Maltase
- Explanation: Brush-border enzymes (e.g., maltase, lactase, sucrase) are present on the intestinal villi to complete carbohydrate digestion.
Q61. The pH of the stomach is maintained around:
a) 2
b) 5
c) 7
d) 8
Answer: a) 2
- Explanation: Gastric juice maintains stomach pH around 1.8–2.5 due to hydrochloric acid, essential for pepsin activation.
Q62. The secretion of bile is stimulated by:
a) Secretin
b) Gastrin
c) CCK (Cholecystokinin)
d) Enterogastrone
Answer: c) CCK (Cholecystokinin)
- Explanation: CCK stimulates the gallbladder to contract and release bile into the duodenum.
Q63. The end product of protein digestion is:
a) Amino acids
b) Glucose
c) Fatty acids
d) Disaccharides
Answer: a) Amino acids
- Explanation: Proteins are digested into amino acids by proteases and peptidases.
Q64. The absorption of glucose in the small intestine occurs by:
a) Active transport
b) Diffusion
c) Osmosis
d) Endocytosis
Answer: a) Active transport
- Explanation: Glucose and amino acids are absorbed into the intestinal epithelium through sodium-dependent active transport.
Q65. Vitamin B12 absorption requires:
a) Pepsin
b) Trypsin
c) Intrinsic factor
d) Lipase
Answer: c) Intrinsic factor
- Explanation: Vitamin B12 binds to intrinsic factor secreted by gastric parietal cells, which is necessary for absorption in the ileum.
Q66. The sphincter present at the junction of the stomach and duodenum is:
a) Cardiac sphincter
b) Pyloric sphincter
c) Ileocecal valve
d) Anal sphincter
Answer: b) Pyloric sphincter
- Explanation: The pyloric sphincter regulates the passage of partially digested food (chyme) from the stomach to the duodenum.
Q67. The gastric glands secrete all except:
a) Mucus
b) Pepsinogen
c) Hydrochloric acid
d) Amylase
Answer: d) Amylase
- Explanation: Amylase is secreted by salivary glands and pancreas, not by gastric glands.
Q68. Which enzyme breaks down nucleic acids?
a) Nuclease
b) Pepsin
c) Lipase
d) Trypsin
Answer: a) Nuclease
- Explanation: Pancreatic nucleases such as DNAse and RNAse break down nucleic acids into nucleotides.
Q69. The process of ingestion of food is regulated by:
a) Hypothalamus
b) Cerebellum
c) Medulla oblongata
d) Pons
Answer: a) Hypothalamus
- Explanation: The hypothalamus controls hunger and satiety centers, regulating ingestion of food.
Q70. Which part of the small intestine receives bile and pancreatic juice?
a) Ileum
b) Duodenum
c) Jejunum
d) Colon
Answer: b) Duodenum
- Explanation: The duodenum is the first part of the small intestine where bile and pancreatic secretions enter for digestion.
Q71. Kupffer cells are specialized cells of the liver that function as:
a) Hormone producers
b) Phagocytes
c) Enzyme secreting cells
d) Fat absorbers
Answer: b) Phagocytes
- Explanation: Kupffer cells are liver macrophages that destroy pathogens and old RBCs in the liver sinusoids.
Q72. Which of the following is not a component of gastric juice?
a) Pepsinogen
b) Intrinsic factor
c) Hydrochloric acid
d) Amylase
Answer: d) Amylase
- Explanation: Gastric juice contains pepsinogen, HCl, mucus, and intrinsic factor, but not amylase.
Q73. The major part of digestion and absorption of food occurs in:
a) Stomach
b) Small intestine
c) Large intestine
d) Esophagus
Answer: b) Small intestine
- Explanation: The small intestine is the principal site for enzymatic digestion and nutrient absorption.
Q74. Which is the correct sequence of layers of the alimentary canal from inside to outside?
a) Muscularis → Serosa → Submucosa → Mucosa
b) Mucosa → Submucosa → Muscularis → Serosa
c) Serosa → Muscularis → Submucosa → Mucosa
d) Submucosa → Mucosa → Serosa → Muscularis
Answer: b) Mucosa → Submucosa → Muscularis → Serosa
- Explanation: The alimentary canal wall has four concentric layers arranged from innermost to outermost as mucosa, submucosa, muscularis, and serosa.
Q75. Which one of the following is NOT a function of the liver?
a) Detoxification
b) Bile secretion
c) Urea synthesis
d) Secretion of digestive enzymes
Answer: d) Secretion of digestive enzymes
- Explanation: The liver secretes bile but not digestive enzymes. Enzyme secretion is done by pancreas, salivary glands, and stomach.
Part 4: Human Physiology – Digestion and Absorption (Q76–Q100)
Q76. Which enzyme is secreted in an inactive form in the stomach?
a) Pepsin
b) Trypsin
c) Pepsinogen ✅
d) Lipase
Explanation:
- (a) Pepsin – Active form, not secreted directly.
- (b) Trypsin – Secreted as trypsinogen from the pancreas.
- (c) Pepsinogen – Secreted in inactive form, activated by HCl → pepsin. ✅
- (d) Lipase – Secreted as active enzyme.
Q77. Which cells of the stomach secrete hydrochloric acid?
a) Chief cells
b) Goblet cells
c) Oxyntic (parietal) cells ✅
d) G-cells
Explanation:
- (a) Chief cells – Secrete pepsinogen.
- (b) Goblet cells – Secrete mucus.
- (c) Oxyntic cells – Secrete HCl and intrinsic factor. ✅
- (d) G-cells – Secrete gastrin hormone.
Q78. Which enzyme hydrolyzes starch into maltose in the intestine?
a) Amylase ✅
b) Maltase
c) Sucrase
d) Lactase
Explanation:
- (a) Amylase – Breaks starch → maltose. ✅
- (b) Maltase – Maltose → glucose.
- (c) Sucrase – Sucrose → glucose + fructose.
- (d) Lactase – Lactose → glucose + galactose.
Q79. Which vitamin requires intrinsic factor for absorption?
a) Vitamin A
b) Vitamin B6
c) Vitamin B12 ✅
d) Vitamin K
Explanation:
- (a) Vitamin A – Absorbed with fat.
- (b) Vitamin B6 – Absorbed without intrinsic factor.
- (c) Vitamin B12 – Needs intrinsic factor secreted by parietal cells. ✅
- (d) Vitamin K – Fat-soluble vitamin absorbed with bile salts.
Q80. Bile salts are responsible for:
a) Protein digestion
b) Emulsification of fats ✅
c) Hydrolysis of starch
d) Secretion of HCl
Explanation:
- (a) Proteins – Digested by proteases.
- (b) Bile salts break fats into small droplets (emulsification). ✅
- (c) Starch – Digested by amylases.
- (d) HCl is secreted by parietal cells, not bile.
Q81. Which digestive enzyme is secreted by salivary glands?
a) Pepsin
b) Salivary amylase ✅
c) Trypsin
d) Lipase
Explanation:
- (a) Pepsin – Stomach.
- (b) Salivary amylase – Starts starch digestion in mouth. ✅
- (c) Trypsin – Pancreas.
- (d) Lipase – Pancreas.
Q82. Rennin (chymosin) in infants helps in digestion of:
a) Fats
b) Carbohydrates
c) Milk proteins ✅
d) Nucleic acids
Explanation:
- (a) Fats – Digested by lipase.
- (b) Carbohydrates – Digested by amylase.
- (c) Rennin coagulates milk protein casein in infants. ✅
- (d) Nucleic acids – Digested by nucleases.
Q83. Which hormone stimulates secretion of pancreatic enzymes?
a) Secretin
b) Gastrin
c) Cholecystokinin (CCK) ✅
d) Insulin
Explanation:
- (a) Secretin – Stimulates bicarbonate secretion.
- (b) Gastrin – Stimulates gastric juice secretion.
- (c) CCK – Stimulates release of pancreatic enzymes + bile. ✅
- (d) Insulin – Regulates blood glucose.
Q84. Which of the following is not an enzyme?
a) Pepsin
b) Trypsin
c) Gastrin ✅
d) Lipase
Explanation:
- (a) Pepsin – Enzyme.
- (b) Trypsin – Enzyme.
- (c) Gastrin – Hormone, not an enzyme. ✅
- (d) Lipase – Enzyme.
Q85. The primary site of absorption of nutrients is:
a) Stomach
b) Small intestine ✅
c) Large intestine
d) Liver
Explanation:
- (a) Stomach – Mostly digestion, little absorption.
- (b) Small intestine – Main site of nutrient absorption. ✅
- (c) Large intestine – Mainly water absorption.
- (d) Liver – Metabolism, not absorption site.
Q86. Which enzyme digests nucleic acids?
a) Amylase
b) Nuclease ✅
c) Lipase
d) Protease
Explanation:
- (a) Amylase – Carbohydrates.
- (b) Nucleases digest DNA and RNA. ✅
- (c) Lipase – Lipids.
- (d) Protease – Proteins.
Q87. Which part of the small intestine receives bile and pancreatic juice?
a) Duodenum ✅
b) Jejunum
c) Ileum
d) Colon
Explanation:
- (a) Duodenum – First part, receives bile + pancreatic juice. ✅
- (b) Jejunum – Absorption.
- (c) Ileum – Absorption, Vitamin B12.
- (d) Colon – Water absorption.
Q88. Which enzyme is responsible for the final step of protein digestion?
a) Pepsin
b) Trypsin
c) Dipeptidase ✅
d) Enterokinase
Explanation:
- (a) Pepsin – Initial protein digestion.
- (b) Trypsin – Breaks proteins → peptides.
- (c) Dipeptidase – Breaks dipeptides into amino acids. ✅
- (d) Enterokinase – Activates trypsinogen.
Q89. The brush border cells of the intestine secrete:
a) Enterokinase ✅
b) Pepsin
c) Rennin
d) Lipase
Explanation:
- (a) Enterokinase – Secreted by brush border, activates trypsinogen. ✅
- (b) Pepsin – Stomach.
- (c) Rennin – Infants’ stomach.
- (d) Lipase – Pancreatic.
Q90. Which organ stores bile?
a) Liver
b) Pancreas
c) Gallbladder ✅
d) Spleen
Explanation:
- (a) Liver – Produces bile.
- (b) Pancreas – No bile function.
- (c) Gallbladder – Stores and releases bile. ✅
- (d) Spleen – Blood filtration, not bile.
Q91. Which hormone stimulates HCl secretion in stomach?
a) Secretin
b) Gastrin ✅
c) CCK
d) GIP
Explanation:
- (a) Secretin – Pancreatic bicarbonate.
- (b) Gastrin – Stimulates gastric glands to secrete HCl. ✅
- (c) CCK – Pancreatic enzymes + bile.
- (d) GIP – Inhibits gastric secretion.
Q92. Which part of the digestive system absorbs maximum water?
a) Stomach
b) Small intestine
c) Large intestine ✅
d) Rectum
Explanation:
- (a) Stomach – Very little absorption.
- (b) Small intestine – Nutrients absorption.
- (c) Large intestine – Absorbs most water and electrolytes. ✅
- (d) Rectum – Storage, not absorption.
Q93. Which enzyme activates trypsinogen into trypsin?
a) Pepsin
b) Enterokinase ✅
c) Lipase
d) Rennin
Explanation:
- (a) Pepsin – Protein digestion in stomach.
- (b) Enterokinase – Converts trypsinogen → trypsin. ✅
- (c) Lipase – Lipid digestion.
- (d) Rennin – Coagulates milk proteins.
Q94. The major site of carbohydrate digestion is:
a) Mouth
b) Stomach
c) Small intestine ✅
d) Large intestine
Explanation:
- (a) Mouth – Initial starch digestion.
- (b) Stomach – Minimal carbohydrate digestion.
- (c) Small intestine – Major carbohydrate digestion and absorption. ✅
- (d) Large intestine – No carbohydrate digestion.
Q95. Which vitamin deficiency causes pernicious anemia due to lack of intrinsic factor?
a) Vitamin A
b) Vitamin D
c) Vitamin B12 ✅
d) Vitamin K
Explanation:
- (a) Vitamin A – Vision defect.
- (b) Vitamin D – Rickets.
- (c) Vitamin B12 deficiency → pernicious anemia (requires intrinsic factor). ✅
- (d) Vitamin K – Blood clotting issues.
Q96. Which enzyme digests milk sugar (lactose)?
a) Maltase
b) Sucrase
c) Lactase ✅
d) Amylase
Explanation:
- (a) Maltase – Maltose.
- (b) Sucrase – Sucrose.
- (c) Lactase – Lactose → glucose + galactose. ✅
- (d) Amylase – Starch.
Q97. Which part of the alimentary canal contains villi?
a) Esophagus
b) Stomach
c) Small intestine ✅
d) Large intestine
Explanation:
- (a) Esophagus – Only transport.
- (b) Stomach – No villi.
- (c) Small intestine – Villi increase surface area for absorption. ✅
- (d) Large intestine – No villi, only folds.
Q98. The hormone secretin was discovered by:
a) Bayliss and Starling ✅
b) Banting and Best
c) Watson and Crick
d) Fleming
Explanation:
- (a) Bayliss and Starling discovered secretin in 1902. ✅
- (b) Banting and Best – Insulin.
- (c) Watson and Crick – DNA structure.
- (d) Fleming – Penicillin.
Q99. Which enzyme digests emulsified fats?
a) Lipase ✅
b) Amylase
c) Trypsin
d) Maltase
Explanation:
- (a) Lipase – Digests fats into glycerol + fatty acids. ✅
- (b) Amylase – Starch.
- (c) Trypsin – Proteins.
- (d) Maltase – Carbohydrates.
Q100. The process of breakdown of large fat globules into smaller droplets by bile salts is called:
a) Hydrolysis
b) Emulsification ✅
c) Coagulation
d) Absorption
Explanation:
- (a) Hydrolysis – Enzymatic breakdown.
- (b) Emulsification – Bile salts break fats into small droplets. ✅
- (c) Coagulation – Protein clumping.
- (d) Absorption – Uptake of digested products.
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