Q.Though the bile juice of liver has no digestive enzyme, but it is very essential for proper digestion of food, especially of the fats. Discuss the following.

Bile has no digestive enzymes, but its bile salts emulsify dietary fat into tiny droplets, dramatically increasing the surface area available for lipase to act on, and also help absorb fat-soluble vitamins and neutralise acidic chyme.

(a) Composition of bile: bile is a greenish-yellow secretion of the liver, stored and concentrated in the gallbladder before release into the duodenum. It is mainly composed of:

• Water — the major component.
• Bile salts (e.g., sodium glycocholate, sodium taurocholate) — these are the functionally important component for digestion.
• Bile pigments — bilirubin and biliverdin, breakdown products of haemoglobin from worn-out red blood cells, which give bile (and faeces) their characteristic colour.
• Cholesterol and phospholipids (lecithin) — lipid components.
• Electrolytes (bicarbonate and other ions) that make bile alkaline.

(b) Role in digestion: even though bile itself contains no digestive enzymes, it is essential for fat digestion and absorption in these ways:

1. Emulsification of fats: bile salts act like a detergent, breaking large fat globules into much smaller droplets (emulsification). This greatly increases the total surface area of fat exposed to the enzyme lipase (secreted by the pancreas), making enzymatic digestion of fat far more efficient than it would be on large, undispersed fat globules. …