Infection and Response

• Pathogens are microorganisms that cause infectious (communicable) diseases. They can infect plants and animals.
• Pathogens can spread by direct contact, water and air or vectors.
• Vectors are organisms that carry a disease without being affected by it.
• Viruses reproduce rapidly in body cells causing damage to the cells.
• Bacteria may damage cells directly or produce toxins (poisons) that damage tissues.
• Protists are single celled organisms that unlike bacteria, are eukaryotic.
• The body has a number of non - specific defences against disease These defend the body against pathogens.
• If a pathogen enter the body, the immune system tries to destroy it.
• White blood cells defend against pathogens through a process called phagocytosis. This is where the pathogen is surrounded, engulfed and digested.
• White blood cells produce antibodies (special protein molecules) which attach to antigen molecules on a pathogen.
• White blood cells produce antitoxins, which are chemicals that neutralise the poisonous effects of the toxins.
• When a pathogen tries to re-enter the body, white blood cells respond more quickly to produce the correct antibodies. This response reduces the likelihood of geting ill and is known as immunity
• Antibiotics are medicines that can kill bacteria, but not viruses.
• MRSA is a strain of bacteria that is resistant to antibiotics.
• Aspirin is a pain killer that originates from willow.
• Penicillin was discovered by Alexander Fleming from the Penicillium mould.
• Double-blind trials are where the doctor and the patient does not know whether they are given the real drug or not.
• The placebo is when you are led to believe that the drug you are given will help against certain symptoms, but in reality it does not.
• Monoclonal antibodies are produced from a single cell that has divided to make many cloned copies of itself.
• Monoclonal antibodies are produced by combining mouse cells and a tumour cell to make a cell called hybridoma.
• Monoclonal antibodies are used in pregnancy tests to bind the hormone HCG, found in urine during early pregnancy.
• Tobacco mosaic virus is a widespread plant pathogen: It infects tobacco and many other plants and produces a mosaic pattern of discolouration on the leaves. This affects photosynthesis.
• Aphids are small insects that feed from the phloem, taking sugars away from the plant.
• Deficiency diseases are diseases that are caused by a lack of mineral ions in the soil. For example, Chlorosis is caused by magnesium deficiency.
• Mimicry is used stop animals from eating plants, by making the plant look dangerous.