▶️ Answer/Explanation
(a)
The completed table identifies the structures and functions based on the diagram:
| Name of Structure | Function | Letter |
|---|---|---|
| Anus | Egestion / removal of undigested food / faeces | G |
| Salivary glands / Pancreas | Produces amylase | M / D |
| Gall bladder | Stores bile | L |
| Oesophagus | Transports food to the stomach | B |
Explanation: Structure G is the exit point of the alimentary canal (anus), responsible for egestion. Amylase is produced in the salivary glands (M) and the pancreas (D). The gall bladder (L) stores bile produced by the liver. Structure B is the tube connecting the mouth to the stomach (oesophagus).
(b)(i)
Chemical digestion is the breakdown of large, insoluble molecules into small, soluble molecules so that they can be absorbed into the blood.
(b)(ii)
Glucose.
Explanation: Maltose is a disaccharide. The enzyme maltase breaks it down into its constituent monosaccharides, which are glucose molecules.
(b)(iii)
Digestion occurs on the membranes of the epithelium lining / epithelial cells (of the small intestine / villi).
(b)(iv)
Amylase acts in the small intestine but not the stomach due to pH differences:
- The stomach produces hydrochloric acid (HCl), creating an acidic pH.
- This low pH denatures the enzyme amylase.
- Denaturation changes the shape of the active site so it is no longer complementary to the substrate (starch), preventing the formation of enzyme-substrate complexes.
- In the small intestine, bile neutralizes the stomach acid, providing the alkaline / suitable pH required for amylase activity.