AQA Biology; Immunity UPDATED VERSION.

AQA Biology; Immunity UPDATED VERSION. What is an antigen? - ANSWER.Molecules, usually proteins, that are on the cell-surface membrane of pathogens that trigger an immune response What is a pathogen? - ANSWER.A disease causing microorganisms What are the 4 main stages of the immune response? - ANSWER.Phagocytosis T-Cells B-Cells Antibody production What happens during phagocytosis? - ANSWER.Chemoattractants from the pathogen attracts the phagocyte, the phagocyte moves to the pathogen. Phagocytes have several receptors on their cell-surface membrane that recognise and attach to chemicals on the surface of the pathogen. They engulf the pathogen and to form a vesicle called a phagosome. Lysosomes move towards the vesicle and fuse. Lysozymes are present in the lysosome and hydrolyse the cell walls of bacteria. The soluble products from the breakdown are absorbed into the cytoplasm of the phagocyte What are your body cells called? - ANSWER.Self What are foreign cells called? - ANSWER.Non-self How is the chance of an organ that has been transplanted being rejected reduced? - ANSWER.Donor is a close match, best matches are usually from relatives that are genetically close Immunosuppressant drugs are also administered to reduce the immune response Why is there a time lag between exposure to the antigen and the body's defences to bring it under control? - ANSWER.As of clonal selection - it takes time for the correct lymphocyte to build up its numbers What are the non-specific mechanisms? - ANSWER.Physical barrier Phagocytosis What are examples of physical barriers? - ANSWER.Skin, mucus, tears, stomach acid What are the specific responses? - ANSWER.Cell mediated response Humoral response