Question What is the function of the immune system? Answer:

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1 Q1 How quickly do bacteria reproduce in ideal conditions? Every 20 minutes. Q2 If you start with 1 bacterium that reproduces every 20 minutes, how many bacteria will you have after 5 hours? Q3 Give three examples of the body s first line of defence? Skin Tears Stomach acid Earwax Mucus Q4 What is the function of the immune system? To deal with any infectious microorganisms that enter the body.

2 Q5 What are the roles of the two types of white blood cell? One type engulfs and digests any foreign material. The other type produces antibodies against specific microorganisms. Q6 What is an antigen? A chemical marker on a cell surface. Antibodies will attach to them if they are the right shape. Q7 What is an antibody? Proteins that are specific to a particular antigen. They are produced by white blood cells. Q8 What do antibodies do? They bind to pathogens and damage or destroy them. They coat pathogens, clumping them together so that they are easily ingested. They bind to and neutralise viruses or toxins.

3 Q9 Explain why you are immune to most diseases that you have already had. Some white blood cells stay in the blood after the original infection has cleared. These memory cells can reproduce quickly if the same antigen is encountered again. This means that the microorganism is killed off before you become ill. Q10 What is a vaccine? It contains dead or inactive microorganisms. These act as antigens. When injected into the body, they stimulate white blood cells to produce antibodies against the pathogen. Q11 What is herd immunity? It is a form of immunity that occurs when the vaccination of a significant portion of a population (or herd) provides a measure of protection for individuals who have not developed immunity. Q12 Why are vaccines not risk free for everyone? Some people may have serious side effects. Genetic differences mean that people react differently.

4 Q13 Why do people need to get a flu vaccination each year, but some diseases only require a single vaccination? The flu virus DNA mutates rapidly this means that it changes its antigens and is no longer recognised by the antibodies. Q14 What is an antimicrobial? A chemical that can inhibit the growth of microorganisms or kill them, without damaging your own body cells. Q15 What is an antibiotic? Q16 What is antibiotic resistance? A chemical that kills bacteria. Antibiotic resistance is when bacteria are no longer killed by an antibiotic.

5 Q17 Explain why antibiotics should not be prescribed for someone with flu. Antibiotics do not kill viruses and so they would not work. Q18 Why are patients advised to finish a course of antibiotics even if they start to feel better? Not finishing the course can increase the risk of antibiotic resistant bacteria emerging. Q19 Describe how new drugs are usually tested before being prescribed for human use. They are tested on human cells, then live mammals (e.g. rats), then on human volunteers. Q20 What is a placebo? Explain why they are sometimes not used in drug trials. A placebo is a fake treatment. In trials where patients are seriously ill, it would be unethical to use a placebo as it would prevent the patient from getting the potential benefits of the new drug.

6 Q21 What is meant by blind, double-blind and open-label clinical trials? Blind the patient doesn t know if they have the placebo or the drug. Double-blind neither the patient or the doctor/scientist know who has the placebo. Open-label everyone is aware of the treatment that has been received. Q22 The heart is a double pump, explain what this means. The right side pumps deoxygenated blood to the lungs, the left side pumps oxygenated blood around the body. Q23 How is the structure of an artery adapted to its function? Arteries have thick, elastic walls to enable them to withstand high pressure. Q24 How is the structure of a vein adapted to its function? Veins have a large lumen to enable blood to flow more easily; they also have valves to ensure that blood flows in the right direction.

7 Q25 Q26 What is heart rate and how could you measure it? Heart rate is the number of times your heart beats in one minute it can be calculated by taking your pulse rate as the pulse is caused by blood being pumped through by a heart beat. When a blood pressure reading is taken, what do the two values actually measure? The higher reading is the pressure of blood when the heart contracts, the lower value is the pressure of the blood when the heart relaxes. Q27 Describe one way in which high blood pressure can lead to heart disease. High blood pressure can damage the lining of an artery. Q28 Give three examples of lifestyle factors that can cause heart disease. Poor diet Smoking Stress Excess alcohol Lack of exercise

8 Q29 Q30 Explain how epidemiological studies can be used to identify the risk factors for heart disease. By studying groups of people it is possible to look for similarities in lifestyles that may be linked to heart disease. What is homeostasis? The maintenance of a constant internal environment. Q31 Name the three main components of the body s automatic control system. Receptor Processing centre Effector Q32 Give two ways that water is gained by the body and two ways in which it is lost. Gained: food, drink, respiration Lost: sweating, breathing, in faeces and urine.

9 Q33 Q34 What factors can increase the concentration of urine produced by the kidneys? External temperature Exercise Intake of fluid and salts Which gland releases ADH? The pituitary gland. Q35 If there is an increase in water content in the blood, will more or less ADH be released? Less. Q36 What effect does alcohol have on urine production, why? It inhibits ADH production, so the kidneys reabsorb less water. Urine is more dilute.