Infection and Response

• Pathogens include viruses, bacteria, protists and fungi. They may cause infectious communicable diseases
• Viruses are extremely small, they move into cells and use the biochemistry of the cell to make copies. Potentially resulting in the cell bursting and releasing copies into the bloodstream. The damage makes the victim feel sick
• Bacteria are small and multiply quickly via binary fissions. They produce toxins which can damage cells
• Protists some are parasitic(live on/inside) and may cause damage. They are often transferred by a vector
• Fungi may be single-celled or made of hyphae(thread-like structure). They can produce spores which may spread to other organisms
• Pathogens are spread by Direct contact, water and air. They can be limited by improving hygiene, staying away from vectors, vaccination and reduce contact
• There are 3 main viral diseases. They are Measles, TMV and HIV. Measles are spread by inhaling droplets they cause fever and skin rash which can be prevented by vaccination. TMV is spread by contact with plants. A plant with TMV may have mosaic discolouration, less sugars and stunted growth. TMV can be treated with fungicides and removing infected parts. HIV is spread by exchanging body fluids they have flu-like symptoms and can be treated with antiretroviral drugs
• Rose block spot is a fungal disease spread by wind/water. Rose black spot cause purple and black spots on leaves and can be treated using fungicides and removing infected parts
• Malaria is a protist disease. It is spread by mosquitoes and cause fever. It can be cured by preventing vectors breeding and mosquitos nets
• There are 2 main bacterial diseases Salmonella and Gonorrhoea. Salmonella is spread by eating infected foods and causes fever, cramps, vomiting and diarrhoea. Vaccination, washing hands and disinfecting surfaces. Gonorrhoea is spread by contact and causes discharge or pain
• Non specific defences help prevent pathogens from entering the body. The skin secretes antimicrobial substances and has skin flora. It also acts as a physical barrier. The nose has hair and mucus to trap pathogens. The trachea and bronchi secrete mucus to trap pathogens and cilia to move mucus to be swallowed. The stomach also produces HCl
• Specific defences help prevent pathogens from entering the body. White blood cells help defeat them. They are either phagocytes or lymphocytes. Phagocytosis involves engulfing and digesting pathogens whilst lymphocytes release antitoxins and antibodies
• During vaccination, an inactive pathogen is injected into the muscle. This causes white blood cells to produce antibodies and specific antibodies are produced quickly and destroy the virus
• Virus in injected in the mouse and lymphocytes which produce specific antibodies are collected and combined with a tumour cell to make a hybridoma this is then cloned to make many cells that produce the antibody