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.
Which enzyme breaks down starch?
A) Pepsin
B) Lipase
C) Amylase ✅
D) Trypsin Explanation: Amylase breaks down starch into sugars.
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.
Which organ produces bile?
A) Stomach
B) Liver ✅
C) Gallbladder
D) Pancreas Explanation: The liver produces bile; the gallbladder stores it.
Where is bile stored?
A) Pancreas
B) Small intestine
C) Gallbladder ✅
D) Liver Explanation: The gallbladder stores and concentrates bile.
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.
Pepsin digests:
A) Carbohydrates
B) Proteins ✅
C) Lipids
D) Nucleic acids Explanation: Pepsin, active in the stomach, breaks proteins into peptides.
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.
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.
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.
Which macronutrient begins digestion in the mouth?
A) Protein
B) Fat
C) Carbohydrate ✅
D) Fiber Explanation: Salivary amylase starts breaking down starch.
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.
The pancreas secretes:
A) Bile
B) Hydrochloric acid
C) Digestive enzymes ✅
D) Mucus Explanation: Pancreas releases enzymes like lipase, amylase, and trypsin.
Which structure prevents food from entering the windpipe?
A) Epiglottis ✅
B) Uvula
C) Tongue
D) Pharynx Explanation: The epiglottis covers the larynx during swallowing.
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.
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.
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.
Which nutrient is digested by lipase?
A) Carbohydrates
B) Proteins
C) Fats ✅
D) Vitamins Explanation: Lipase breaks down lipids into fatty acids and glycerol.
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.
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)
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.
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.
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.
Lactose intolerance is caused by deficiency of:
A) Amylase
B) Lipase
C) Lactase ✅
D) Sucrase Explanation: Lactase breaks down lactose; its deficiency causes intolerance.
Which is a brush-border enzyme?
A) Pepsin
B) Sucrase ✅
C) Trypsin
D) Lipase Explanation: Sucrase is located on the microvilli of intestinal cells.
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.
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.
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.
Enterokinase activates:
A) Pepsinogen
B) Trypsinogen ✅
C) Amylase
D) Lipase Explanation: Enterokinase converts trypsinogen to active trypsin.
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.
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.
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.
Which organ secretes both endocrine and exocrine substances?
A) Liver
B) Gallbladder
C) Pancreas ✅
D) Stomach Explanation: The pancreas secretes digestive enzymes and hormones.
Trypsin digests:
A) Carbohydrates
B) Proteins ✅
C) Fats
D) Nucleic acids Explanation: Trypsin breaks down proteins in the small intestine.
Which of the following is a zymogen?
A) Lipase
B) Trypsinogen ✅
C) Amylase
D) Maltase Explanation: Zymogens are inactive enzyme precursors like trypsinogen.
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.
Which vitamin enhances calcium absorption?
A) Vitamin C
B) Vitamin D ✅
C) Vitamin B12
D) Vitamin K Explanation: Vitamin D promotes intestinal calcium absorption.
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.
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.
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)
Which hormone inhibits gastric emptying?
A) Gastrin
B) Secretin
C) Cholecystokinin ✅
D) Insulin Explanation: CCK slows gastric emptying to allow fat digestion.
Pancreatic zymogens are activated by:
A) HCl
B) Enteropeptidase ✅
C) Gastrin
D) Secretin Explanation: Enteropeptidase (enterokinase) activates trypsinogen.
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.
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.
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.
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.
Paneth cells secrete:
A) Mucus
B) Digestive enzymes
C) Antimicrobial peptides ✅
D) Hormones Explanation: Paneth cells release lysozyme and defensins.
Which enzyme digests nucleic acids?
A) Lipase
B) Amylase
C) Nuclease ✅
D) Pepsin Explanation: Nucleases break DNA and RNA into nucleotides.
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.
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.