plants 0.0 / 5 ? Biologyinfection and responseIGCSEAQA Created by: claudia.listerCreated on: 15-04-19 16:46 Life cycle of a virus They can survive outside a host for long periods of time They infect a suitable host cell They replicate themselves thousands of times They copy their genetic material (DNA or RNA) and protein coats This often causes the host cell to burst Other cells can then be infected 1 of 5 Differences between phagocytes and lymphocytes Phagocytes surround any pathogens in your blood and engulf them Enzymes inside the phagocytes then breakdown the pathogen lymphocytes recognise proteins on the surface of pathogens called antigens they then produce antibodies which make pathogens stick together lymphocytes also produce antitoxins to neutralise the effects of toxins produced by pathogens 2 of 5 How pathogens can be transmitted Direct contact which can be sexual or non-sexual Dirty water can transmit many diseases such as the cholera bacterium When a person who is infected by the common cold sneezes they can spray thousands of tiny droplets containing virus particles to infect others undercooked or reheated food can cause diseases like Escherichia coli which is a cause of food poisoning Via another animal called a vector Additional marks for correct pathogens and disease 3 of 5 Effects of viruses on plants The tobacco mosaic virus infects tobacco and other closely related species It infects the chloroplasts of plant leaves It changes their colour from green to yellow or white in a mosaic pattern It can also make leaves crinkled or curled up - this reduces the plant’s ability to photosynthesise, which reduces the crop yield of farmers 4 of 5 Effects of viruses on animals HIV stands for human immunodeficiency virus It is transmitted by body fluids, often during unprotected sex and injecting drugs using dirty needles Immediately after infection, infected people often suffer mild flu-like symptoms AIDS stands for acquired immune deficiency syndrome Months or years after infection the HIV virus becomes active and HIV turns into AIDS it starts to attack the patient’s immune system 5 of 5
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