1. What are "enzymes" and how do they work ?
Answer
Enzymes are biological catalysts that speed up chemical reactions in all living things. They are all proteins and have an active site with a specific shape that the substrate fits into.
2. Describe how an unhealthy lifestyle affects the coronary arteries and list ways of reducing the risk of coronary heart disease.
Answer
An unhealthy lifestyle can cause a build-up of fatty material in the coronary arteries and reduces the supply of oxygenated blood to the heart, eventually causing a heart attack. The risk of coronary heart disease can be reduced by eating a balanced diet, not smoking, exercise and taking statins (drugs that can be used to reduce blood cholesterol levels).
3. The figure below shows the human digestive system. Name the parts labelled A–F.
Answer
4. The liver produces bile that is stored in the gall bladder. Describe the functions of bile.
Answer
Bile is alkaline to neutralise hydrochloric acid from the stomach and provide the optimum pH for lipase. Bile emulsifies fats (breaks large drops of fat into small droplets). This increases the surface area for lipase to act on and speeds up the rate of lipid breakdown.
5. Explain why smoking increases the risk of lung cancer. Name some other lung diseases that smoking increases the risk of.
Answer
Chemicals (called carcinogens) in cigarette smoke damage DNA causing cells to divide uncontrollably. Some other lung diseases are asthma, bronchitis and emphysema.
6. The coronary arteries can be affected by coronary heart disease. Name some factors associated with an increased risk of this disease.
Answer
High fat diet, smoking, high blood cholesterol, lack of exercise.
7. Identify the blood vessels labelled A–C in the figure below.
Answer
8. Describe some ways in which red blood cells are adapted to perform their function.
Answer
Red blood cells contain the red pigment haemoglobin, which binds to oxygen. They have no nucleus, allowing more room for haemoglobin. Their biconcave disc shape provides a large surface area to volume ratio.
9. The graph below shows the relationship between percentage abdominal fat and insulin sensitivity in a group of people. Give some reasons why this graph cannot be used to find out if a person has type 2 diabetes.
Answer
Graph shows a correlation between percentage abdominal fat and insulin sensitivity, not that the percentage abdominal fat causes diabetes. The sample size (22 people) is small. Do not know what level of insulin sensitivity is linked with type 2 diabetes or what level of insulin sensitivity is normal.
10. Cancer causes changes in cells that lead to tumours forming. Describe how tumours form.
Answer
Tumours form through uncontrolled growth and cell division.