Digestion breaks large food molecules into smaller absorbable units. Carbohydrases break carbohydrates into smaller sugars; proteases break proteins into amino acids through smaller peptides; lipases break triglycerides into fatty acids and glycerol-containing products. Mechanical breakdown increases exposed area, while enzymes catalyse chemical breakdown. Bile emulsifies fats but is not a digestive enzyme.
The small intestine is adapted for absorption through folds, villi and microvilli. A thin epithelium and transport networks help transfer nutrients away. Glucose and amino acids enter blood capillaries; many absorbed long-chain lipid products are packaged and enter lacteals in the lymphatic system. Absorption uses diffusion, carrier-mediated and energy-dependent transport. Vesicular processes such as endocytosis take some larger cargo into cells. Digestion and absorption are separate steps.
Example 1
Match protein digestion to an enzyme group and final small building blocks.
Proteases and peptidases break proteins and peptides towards amino acids.
Example 2
An intestinal lining loses many villi. Which capacity decreases directly?
Absorptive surface area decreases, reducing the available area for nutrient uptake.
Watch out:Bile emulsifies fat into small droplets; lipases catalyse lipid breakdown.
Digestion and absorption practice | Year 11 Biology | Ascent Arcade