These eight original questions follow the lessons in nutrition and digestion. They ramp in difficulty and each answer shows the reasoning.
Write your answer first, then open the answer box.
The questions
Question 1. Name the organ where protein digestion begins and the enzyme involved.
Answer
The stomach. The enzyme is pepsin, which works in the acidic conditions produced by hydrochloric acid.
Question 2. State the substrate and the product of salivary amylase.
Answer
The substrate is starch and the product is maltose.
Question 3. Why is bile not called a digestive enzyme?
Answer
Bile does not chemically break down fat. It emulsifies fat into small droplets, which gives lipase a larger surface area to act on.
Question 4. Complete: maltase acts on ______ to form ______.
Answer
Maltase acts on maltose to form glucose.
Question 5. Explain why the lining of the small intestine is well adapted for absorption.
Answer
It has many villi with microvilli, giving a large surface area. The wall is one cell thick, so the diffusion distance is short. A network of capillaries takes absorbed substances away, keeping the concentration gradient steep.
Question 6. Distinguish absorption from assimilation using glucose as an example.
Answer
Absorption is the movement of glucose from the small intestine into the blood capillaries of the villi. Assimilation is the use of glucose by body cells, for example in respiration to release energy or for storage as glycogen.
Question 7. Food P has 12 g protein per 100 g and a 25 g serving. Food Q has 8 g protein per 100 g and a 50 g serving. Which gives more protein per serving?
Answer
P: 12 × 0.25 = 3 g. Q: 8 × 0.5 = 4 g. So one serving of Q gives more protein, although P has more per 100 g.
Question 8. Explain why comparing 12 g (per 100 g) with 4 g (per serving) is not a fair comparison.
Answer
The two values are on different bases. One is for 100 g of food and the other is for a serving of a different mass. A fair comparison puts both on the same basis, per 100 g or per serving.
If you got these wrong
Questions 1 to 3 belong to tracing digestion through the alimentary canal and relating enzymes to substrates and products. Question 4 is also in the enzyme lesson.
Questions 5 and 6 need explaining absorption and assimilation, and questions 7 and 8 need interpreting nutrition information. Log each slip in the mistake log tool.
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