Digestion and Absorption MCQs

77 MCQs with clinical pearls · MBBS Biochemistry · Prof Jariya

Topics covered (4)

Protein Digestion — 23 MCQs
Carbohydrate Digestion — 22 MCQs
Gastrointestinal Secretions and Regulation — 18 MCQs
Lipid Digestion — 14 MCQs

Sample MCQs with clinical pearls

A lean teenager experiences excessive flatulence ,borborygmic sounds, abdominal discomfort and diarrhea after consumption of dairy products. The likely diagnosis is:

A) Adult hypolactasia ✔

B) Celiac disease

C) Fructose intolerance

D) Galactosemia

E) Lactose intolerance

ADULT HYPOLACTASIA is the normal mammalian pattern: lactase activity is high at birth and declines after weaning. It affects most adults of Asian, African and Mediterranean descent - lactase PERSISTENCE is the genetic variant, not the deficiency. Undigested lactose draws water osmotically and is fermented by colonic bacteria to hydrogen, methane and short-chain fatty acids, giving flatulence, borborygmi and diarrhoea. Diagnosis is by hydrogen breath test. MEMORY: 'Losing lactase after weaning is normal; keeping it is the mutation.'

A young man presents with diarrhea, excessive flatulence ,borborygmic sounds and abdominal discomfort after an ice cream party, The likely cause of excessive flatulence are, undigested:

A) Disaccharides ✔

B) Heteropolsaccharides

C) HomoPolysaccharides

D) Monosaccharides

E) Oligosaccharides

Symptoms appearing after a meal rich in DISACCHARIDES point to a brush border disaccharidase deficiency. Undigested disaccharide is osmotically active and is fermented by colonic bacteria, producing gas and short-chain fatty acids - hence flatulence, borborygmi and osmotic diarrhoea. The commonest is lactase deficiency; sucrase-isomaltase deficiency gives the same picture after sucrose and starch. MEMORY: 'Undigested sugar reaching the colon always means gas and water.'

For digestion of starch enzyme is present in :

A) Gastric & deudenal secretions

B) Gastric & intestinal secretions

C) Gastric & pancreatic secretions

D) Saliva & gastric secretions

E) Saliva & pancreatic secretions ✔

Starch digestion uses alpha-amylase from TWO sources: SALIVARY amylase, which starts it in the mouth and is destroyed by gastric acid, and PANCREATIC amylase, which does most of the work in the duodenum. Both hydrolyse internal alpha-1,4 bonds. Note there is NO gastric amylase - the stomach contributes acid and pepsin, not carbohydrate digestion. MEMORY: 'Amylase comes from mouth and pancreas, never from the stomach.'

These are three of 77 MCQs in this section. Every question carries a clinical pearl explaining the reasoning.

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