Digestion and absorption

14 Kerala PSC Lab Technician Gr II practice questions on Digestion and absorption, part of Biochemistry. The first 14 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   What activates trypsinogen to trypsin in the small intestine?

   1. APepsin
   2. BBile salts
   3. CHydrochloric acid
   4. DEnteropeptidase

   Show answerHide answer

   Answer: D · Enteropeptidase

   Enteropeptidase (enterokinase) from the duodenal brush border removes a small peptide from trypsinogen to form trypsin. Trypsin then activates more trypsinogen and the other pancreatic zymogens, such as chymotrypsinogen, proelastase and procarboxypeptidases. Secreting these enzymes as inactive precursors protects the pancreas; early activation inside the gland causes acute pancreatitis.

   • A: Pepsin works in the stomach and does not activate pancreatic zymogens.
   • B: Bile salts emulsify fats; they do not cleave trypsinogen.
   • C: Hydrochloric acid activates pepsinogen in the stomach, not trypsinogen.

2. Question 2 · Medium

   Glucose and galactose are absorbed from the small intestine mainly by:

   1. AFacilitated diffusion through GLUT5
   2. BPinocytosis by enterocytes
   3. CSimple diffusion between cells
   4. DSodium-dependent active transport

   Show answerHide answer

   Answer: D · Sodium-dependent active transport

   SGLT1 on the brush border carries glucose or galactose into the enterocyte together with sodium, and the sodium gradient is kept up by the Na+-K+ ATPase on the basolateral side, so this is secondary active transport. Fructose enters by facilitated diffusion through GLUT5, and all three sugars leave the cell into portal blood through GLUT2. Oral rehydration solution uses this sodium-glucose co-transport to drive water absorption.

   • A: GLUT5 carries fructose, which is absorbed by facilitated diffusion.
   • B: Pinocytosis is not a significant route for sugar absorption.
   • C: Monosaccharides are absorbed mainly through carriers, not by passive diffusion.

3. Question 3 · Hard

   A 50-year-old man with long-standing heavy alcohol use has bulky, greasy stools and weight loss. Fecal fat is raised, but the D-xylose absorption test is normal. The most likely cause is:

   1. ATropical sprue
   2. BCeliac disease
   3. CExocrine pancreatic insufficiency
   4. DLactase deficiency

   Show answerHide answer

   Answer: C · Exocrine pancreatic insufficiency

   Steatorrhea means fat is either not digested or not absorbed. D-xylose is absorbed by the intestinal mucosa without needing digestion, so normal xylose absorption shows that the mucosa is intact. Steatorrhea with a normal xylose test therefore points to maldigestion from lack of pancreatic lipase, here from chronic alcoholic pancreatitis. Celiac disease and tropical sprue damage the mucosa and lower xylose absorption.

   • A: Tropical sprue also injures the mucosa and lowers D-xylose absorption.
   • B: Celiac disease damages the mucosa, so D-xylose absorption would be low.
   • D: Lactase deficiency causes watery diarrhea after milk, not steatorrhea.

4. Question 4 · Medium

   Long-chain fatty acids absorbed by intestinal cells reach the blood mainly through the lymph as:

   1. AChylomicrons
   2. BAlbumin-bound fatty acids
   3. CHDL particles
   4. DMixed micelles

   Show answerHide answer

   Answer: A · Chylomicrons

   Inside the enterocyte, long-chain fatty acids and monoacylglycerol are re-esterified to triacylglycerol, which is packed with cholesterol, phospholipid and apo B-48 into chylomicrons. These are too large to enter blood capillaries, so they pass into the lacteals and reach blood through the thoracic duct. Short- and medium-chain fatty acids go straight to portal blood bound to albumin. Chylomicrons make serum milky after a fatty meal, which is why lipid tests need a fasting sample.

   • B: Albumin carries short- and medium-chain fatty acids in portal blood.
   • C: HDL carries cholesterol from tissues to the liver, not dietary fat.
   • D: Mixed micelles carry digested fat to the brush border in the gut lumen; they do not enter lymph.

5. Question 5 · Easy

   Bloating and diarrhea after drinking milk, common in adults, is usually due to low activity of:

   1. ATrehalase
   2. BPancreatic amylase
   3. CLactase
   4. DSucrase-isomaltase

   Show answerHide answer

   Answer: C · Lactase

   Lactase on the intestinal brush border splits lactose into glucose and galactose, and its activity falls after weaning in most Asian and African adults. Undigested lactose draws water into the bowel and is fermented by colonic bacteria to gas and acids, causing bloating and diarrhea. The stool is acidic and contains reducing sugar, and a lactose tolerance test shows a flat blood glucose curve.

   • A: Trehalase deficiency causes intolerance to mushrooms, which contain trehalose.
   • B: Pancreatic amylase digests starch, not lactose.
   • D: Sucrase-isomaltase deficiency causes intolerance to cane sugar, not milk.

6. Question 6 · Medium

   Pancreatic lipase, with colipase, splits dietary triglyceride mainly into:

   1. AGlycerol and three fatty acids
   2. BPhosphatidic acid and fatty acids
   3. CDiacylglycerol and one fatty acid
   4. D2-Monoacylglycerol and two fatty acids

   Answer and explanation in LearnFree account

7. Question 7 · Easy

   Which hormone makes the gallbladder contract and the pancreas secrete its enzymes?

   1. ASomatostatin
   2. BGastrin
   3. CCholecystokinin
   4. DSecretin

   Answer and explanation in LearnFree account

8. Question 8 · Hard

   A man with greasy, foul stools is put on a diet with 100 g fat per day. A 72-hour stool collection contains 45 g of fat (normal fecal fat below 7 g/day). How is the result best reported?

   1. A15 g/day: within normal
   2. B15 g/day: steatorrhea
   3. C45 g/day: steatorrhea
   4. D5 g/day: within normal

   Answer and explanation in LearnFree account

9. Question 9 · Easy

   Ptyalin, the starch-digesting enzyme of saliva, is also called:

   1. APepsin
   2. BLingual lipase
   3. CSalivary amylase
   4. DMaltase

   Answer and explanation in LearnFree account

10. Question 10 · Medium

    Bile salts help in the digestion and absorption of fat mainly by:

    1. AHydrolyzing triglycerides to fatty acids
    2. BActivating pancreatic trypsinogen
    3. CNeutralizing acid entering the duodenum
    4. DEmulsifying fat and forming micelles

    Answer and explanation in LearnFree account

11. Question 11 · Medium

    Pepsinogen secreted by the chief cells of the stomach is first converted to active pepsin by:

    1. ATrypsin
    2. BBile salts
    3. CHydrochloric acid
    4. DEnteropeptidase

    Answer and explanation in LearnFree account

12. Question 12 · Hard

    A 9-year-old boy has a red, scaly rash on sun-exposed skin and bouts of unsteady gait. His diet is adequate. Urine chromatography shows large amounts of neutral amino acids (alanine, serine, tryptophan), with normal plasma levels. What is the most likely diagnosis?

    1. APellagra from poor diet
    2. BPhenylketonuria
    3. CHartnup disease
    4. DCystinuria

    Answer and explanation in LearnFree account

13. Question 13 · Easy

    Which carrier takes up fructose across the brush border of intestinal cells?

    1. AGLUT4
    2. BSGLT1
    3. CGLUT1
    4. DGLUT5

    Answer and explanation in LearnFree account

14. Question 14 · Medium

    Why are medium-chain triglycerides given to patients with fat malabsorption?

    1. AThey are stored in the gut wall for later use
    2. BThey are digested by salivary amylase
    3. CThey need extra bile to form micelles
    4. DThey are absorbed straight into portal blood

    Answer and explanation in LearnFree account