1. Explain what "double circulation" means.
Answer
It has two circuits (pulmonary and systemic) so the blood goes through the heart twice.
2. Explain what is meant by the term "risk factor", and give examples of risk factors and their associated diseases.
Answer
Risk factors are linked to an increased rate of a disease. Poor diet, alcohol or smoking can increase the risk of type 2 diabetes and cancer. Substances in a person's body or environment (carcinogenic chemicals or ionising radiation) can increase the risk of cancer.
3. Describe how we could test a sample of food to find out whether it contains carbohydrates, lipids and proteins.
Answer
Put four test tubes into a test tube rack and add a sample of liquid food to each test tube.
Add Benedict's solution to the food then stand the tube in a water bath of hot water (80°C). If the colour changes from blue to brickred then sugar is present.
Add iodine solution to a tube and if the colour changes from orange-brown to blue-black, then there is starch in the food.
Add ethanol to a tube and shake thoroughly then add water. If the solution turns milky white, then the food contains lipid.
Add Biuret solution to the final tube and a colour change from blue to purple shows that there is protein present.
4. The figure below shows the effect of temperature on enzyme activity. Describe and explain how increasing the temperature affects the rate of reaction.
Answer
As temperature increases from 0°C to 41°C, the rate of reaction increases. This is because the enzyme and substrate molecules have more kinetic energy, so more successful collisions take place. The enzyme works best at 41°C, the enzyme's optimum temperature. Above 41°C, the rate of reaction starts to decrease because the enzymes start to denature. This is when the active site changes shape and an enzyme is permanently damaged.
5. Describe two possible effects of smoking on unborn babies.
Answer
Increased risk of miscarriage, premature birth or low birth weight.
6. Heart valves play a critical role in blood circulation. Give one heart valve fault that can occur and how is it treated ?
Answer
The fault may prevent the valve from opening or closing properly. Faulty heart valves can be replaced using biological (or mechanical) valves.
7. Explain the benefit of the slow rate of blood flow in a capillary.
Answer
More time for exchange of materials by diffusion between blood and body cells.
8. Communicable and non-communicable diseases are major causes of ill health. Give two other factors that can affect both physical and mental health.
Answer
Diet, stress and life situations (such as bereavements, money issues, and so on).
9. Describe the short-term and long-term effects that alcohol can have on brain function.
Answer
Short term effects include slower reaction times, loss of balance and slurred speech. Long term effects include memory problems, anxiety, depression and reduced brain function.
10. Describe how tumours can spread to other parts of the body.
Answer
Malignant tumours can spread through the blood, via the circulatory system.