NDA (II) 2022 General Ability Test · Question 77 of 150

Correct — B, bile and lipase. Fat digestion in the small intestine is a two-stage job. Bile, made by the liver, stored in the gall bladder and poured into the duodenum, breaks large fat globules into tiny droplets — emulsification — which hugely increases the surface area exposed to enzymes. Pancreatic lipase then hydrolyses those droplets into fatty acids and glycerol. Bile itself contains no digestive enzyme, so neither partner can finish the job alone, and that is why the answer names both.

• (a)trypsin — Trypsin is a protease secreted by the pancreas; it splits proteins into smaller peptides and has no action on fat.
• (c)bile and amylase — Amylase acts on starch, converting it into maltose and other sugars. Adding bile emulsifies the fat but leaves it chemically undigested, because amylase cannot break a fat molecule.
• (d)bile and pepsin — Pepsin is the protein-digesting enzyme of the stomach and works only in a strongly acidic medium. The small intestine is alkaline, and pepsin has no action on fat in any case.

Digestion of fat needs a physical step before a chemical one. Bile salts are detergents, not enzymes — they emulsify fat so that the water-soluble enzymes can reach it. Pancreatic lipase, delivered to the duodenum in pancreatic juice, then breaks the emulsified fat down into fatty acids and glycerol, which are absorbed through the villi of the small intestine.

The trap is that many students remember the half-sentence 'bile digests fat' and stop. Bile only prepares the fat; the chemical breakdown is done by an enzyme, and the fat-splitting enzyme is lipase. Once you fix that, the options sort themselves — amylase belongs to starch, pepsin and trypsin belong to protein.

• Bile is produced by the liver, stored and concentrated in the gall bladder, and released into the duodenum through the bile duct.
• Bile salts emulsify fat, breaking large globules into small droplets and greatly increasing the surface available for enzyme action.
• Pancreatic lipase hydrolyses emulsified fat into fatty acids and glycerol.
• Bile is alkaline and also neutralises the acidic food paste arriving from the stomach, giving pancreatic enzymes the pH they need to work.

• Calling bile an enzyme; it is a secretion of bile salts and pigments with no enzyme of its own.
• Choosing pepsin or trypsin because they are the most famous digestive enzymes — both act on protein, not fat.

Match a class of nutrient to the exact secretion plus enzyme that acts on it, with the wrong enzyme paired to the right secretion.

• practice — not a real PYQ

  Bile secreted by the liver is stored in the

  • (a)pancreas
  • (b)gall bladder
  • (c)duodenum
  • (d)spleen

  Answer(b) gall bladder — bile is stored and concentrated there and released into the duodenum when fatty food arrives.

• practice — not a real PYQ

  The end products of complete digestion of fat in humans are

  • (a)amino acids
  • (b)glucose and fructose
  • (c)fatty acids and glycerol
  • (d)maltose and dextrin

  Answer(c) fatty acids and glycerol — produced when lipase hydrolyses emulsified fat.