Example 1
Match protein digestion to an enzyme group and final small building blocks.
Proteases and peptidases break proteins and peptides towards amino acids.
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Year 11 · SACE Stage 1
Digestion and absorption
Match digestive products and enzymes, then identify routes of nutrient absorption.
Method and worked examples
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
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.