Module 1 · Answers
Answers & explanations
Brief reasoning included where the answer needs more than a fact.
Section A — Easy
01
Independent (changed), dependent (measured), control (kept the same).
02
Carbohydrates.
03
Iodine — starch. Benedict's — sugar. Biuret — protein. Ethanol (then water) — fat.
04
Mouth → oesophagus → stomach → small intestine → large intestine.
05
Nicotine — addictive, raises heart rate. Tar — causes cancer / coats airways. Carbon monoxide — reduces oxygen carried by red blood cells.
06
Lack of iron.
Section B — Medium
07
Bread contains starch (iodine positive) but no reducing sugar (Benedict's negative).
08
It is long and folded into villi, giving a huge surface area. The villi have thin walls and a rich blood supply, so nutrients diffuse into the blood quickly.
09
Amylase: starch → sugar (glucose). Protease: protein → amino acids. Lipase: fat → fatty acids + glycerol.
10
CO binds to red blood cells, so less oxygen is carried to muscles. With less oxygen, muscles tire faster.
11
Independent: temperature. Dependent: rate of starch breakdown (or time taken). Control: amount of amylase, amount of starch, pH.
Section C — Hard
12
The liver makes bile, which emulsifies fats (breaks them into smaller droplets) so lipase can digest them faster. A damaged liver makes less bile, so fats are digested slowly and may not be fully absorbed.
13
Skipping breakfast misses out on energy and nutrients the body needs after sleep. The drop in blood sugar makes you tired, less able to concentrate, and more likely to overeat at the next meal — which usually means weight gain, not loss. Better to eat balanced meals across the day.
14
Alcohol is a depressant — it slows signals in the nervous system. Reactions become slower, judgement is impaired and coordination worsens, all of which make driving more dangerous.
15
If villi are flattened, the surface area for absorption is much smaller. Less nutrient is absorbed into the blood, so the person can become deficient (low energy, weight loss, missing vitamins/minerals) even if they eat enough food. (This is what happens in coeliac disease.)