Question 1

Which of the following best describes the primary mechanism by which glucose is absorbed from the lumen of the small intestine into the blood?

Accepted Answer

Cotransport with Na+ via secondary active transport across the apical membrane, followed by facilitated diffusion across the basolateral membrane

Question 2

A patient with lactose intolerance experiences diarrhea after consuming dairy products. Which physiological mechanism best explains this symptom?

Accepted Answer

Undigested lactose creates an osmotic gradient in the intestine, preventing water absorption

Question 3

Which enzyme is responsible for initiating protein digestion in the stomach, and at what pH is it most active?

Accepted Answer

Pepsin; pH 1.5–2.5

Question 4

Which of the following best describes the absorption pathway for short-chain fatty acids in the small intestine?

Accepted Answer

They diffuse directly into the capillary blood of the villi

Question 5

Which transporter is responsible for the absorption of fructose across the apical membrane of enterocytes?

Accepted Answer

GLUT5

Question 6

A patient with celiac disease has damaged intestinal villi. Which of the following is a likely consequence?

Accepted Answer

Decreased absorption of nutrients due to loss of surface area and brush border enzymes

Question 7

Which of the following steps is NOT directly involved in the digestion and absorption of dietary lipids?

Accepted Answer

Cotransport with Na+ across the apical membrane

Question 8

Which vitamin requires binding to intrinsic factor for absorption, and by what process is it absorbed?

Accepted Answer

Vitamin B12; endocytosis

Question 9

Which of the following best explains why sodium absorption is closely linked to glucose and amino acid absorption in the small intestine?

Accepted Answer

Sodium cotransporters use the Na+ gradient to drive secondary active transport of glucose and amino acids

Question 10

Which of the following is the correct sequence of events for the absorption of dietary fats?

Accepted Answer

Emulsification → Digestion → Micelle formation → Diffusion → Chylomicron formation → Lymphatic transport

Question 11

Which of the following best describes the absorption of amino acids in the small intestine?

Accepted Answer

Cotransport with Na+ or H+ across the apical membrane, then facilitated diffusion across the basolateral membrane

Question 12

A patient with cystic fibrosis has thick mucus blocking the pancreatic duct. Which of the following is a likely consequence?

Accepted Answer

Decreased digestion and absorption of fats and proteins due to lack of pancreatic enzymes

Question 13

Which of the following is true regarding water absorption in the gastrointestinal tract?

Accepted Answer

About 95% of water is absorbed in the small intestine by osmosis

Question 14

Which of the following best explains why tight junctions between intestinal epithelial cells are important for absorption?

Accepted Answer

They force nutrients to pass through cells, ensuring selective absorption

Question 15

Which of the following is a consequence of a deficiency in brush border enzymes?

Accepted Answer

Incomplete digestion of disaccharides and peptides

Question 16

Which of the following best describes the absorption of nucleic acid digestion products?

Accepted Answer

Breakdown products are actively transported by carriers in the epithelium of villi

Question 17

Which hormone regulates calcium absorption in the small intestine, and what vitamin is required for this process?

Accepted Answer

Parathyroid hormone (PTH); Vitamin D

Question 18

Which of the following is a common age-related change in the digestive system?

Accepted Answer

Slower peristalsis and decreased absorption efficiency

Question 19

Which of the following best explains why chylomicrons are transported via lymphatic lacteals rather than directly into the blood capillaries?

Accepted Answer

Chylomicrons are too large to enter blood capillaries directly

Mechanisms of Digestion and Absorption: A Mini-Textbook Study Guide

Study Guide - Practice Questions