����ý

Four from the following:

1. they can often survive outside a host for long periods of time [1 mark]
2. they then infect a suitable host cell [1 mark]
3. they replicate themselves thousands of times [1 mark]
4. they copy their genetic material (DNA or RNA) and protein coats [1 mark]
5. this often causes the host cell to burst [1 mark]
6. other cells can then be infected [1 mark]

Four from the following:

1. the leaves turn yellow or white [1 mark]
2. they also become crinkled or curled [1 mark]
3. this reduces photosynthesis in chloroplasts [1 mark]
4. which means plants have less glucose for respiration [1 mark]
5. so do not grow as well [1 mark]

Four from the following:

1. phagocytes surround any pathogens in your blood and engulf them [1 mark]
2. enzymes inside the phagocytes then breakdown the pathogen [1 mark]
3. lymphocytes recognise proteins on the surface of pathogens called antigens [1 mark]
4. they then produce antibodies which make pathogens stick together [1 mark]
5. lymphocytes also produce antitoxins to neutralise the effects of toxins produced by pathogens [1 mark]

Four from the following:

1. risk factors are things that increase a person’s chance of developing a disease [1 mark]
2. they can be part of a person’s lifestyle [1 mark]
3. they can be substances in a person’s body or their environment [1 mark]
4. smoking is a risk factor for lung cancer [1 mark]
5. tar in cigarettes is a carcinogen [1 mark]