A dentist examined the diet record of a 10-year-old child with tooth decay. Fig. 1 shows a molar tooth with a cavity in its enamel. cavityenamel layer Item ...
Question 1 Report
A dentist examined the diet record of a 10-year-old child with tooth decay. Fig. 1 shows a molar tooth with a cavity in its enamel.
| Item consumed per day | Number of times |
|---|---|
| Sweetened drink | 5 |
| Fruit | 2 |
| Water | 1 |
(a) Describe the evidence in Table 1 that the child often consumes sugar. [1]
(b) Suggest how bacteria in the mouth can cause the cavity shown in Fig. 1. [2]
(c) Name the type of digestion that chewing starts. [1]
(d) What is the benefit of breaking food into smaller pieces before enzymes act? [1]
A student made a model stomach from a sealed plastic bag. Fig. 1 shows food cubes, acid and protease being mixed by squeezing the bag.
After 20 minutes at 37 degrees C, the student tested the liquid for protein.
(a) Describe how squeezing the bag models the action of stomach muscles. [1]
(b) Suggest why the food cubes became smaller. [1]
(c) Use the model to describe two conditions needed by protease in the stomach. [2]
(d) What is the purpose of mixing food with digestive juices? [1]
Answer Details
Tooth decay
- (a) The child consumed a sweetened drink five times each day. This is evidence of frequent sugar consumption. [1]
- (b) Mouth bacteria feed on sugar and produce acid. The acid damages or dissolves tooth enamel, producing a cavity. [2]
- (c) Chewing starts mechanical digestion. [1]
- (d) Smaller food pieces have a larger surface area for enzyme action. [1]
Model stomach
- (a) Squeezing the bag churns and mixes the food, like contractions of stomach muscles. [1]
- (b) Protease digested protein in the food cubes, so the cubes became smaller. [1]
- (c) The model shows that protease needs a warm temperature, about 37 degrees C, and acidic conditions. [2]
- (d) Mixing food with digestive juices increases contact between food and enzymes. [1]
Key distinction: chewing and churning are mechanical digestion; protease breaking down protein is chemical digestion.
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