Biology Cheat Sheet

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1. Detecting ‘self’ and ‘non self’ molecules: the role of antigens and the membrane receptors. Class I MHC molecules | Class II MHC molecules |
* Are found on almost all nucleated cells of the body (so are not on red blood cells) * Body Cells that have become infected or become cancerous can display antigens by using their Class I MHC molecules on their cell surface * These antigens that get displayed were made inside these cells * Cytotoxic T cells will recognise antigens displayed in this way and will destroy infected cell| * Are only found on certain cells (usually B cells, macrophages and dendritic cells) * These cells are generally known as antigen presenting cells (APCs) * These antigens presented in this case were taken in and degraded by these cells (by endocytosis or phagocytosis) * The foreign material is broken down, and antigens displayed on the cell surface via Class II MHC molecules * Helper T cells recognise antigens displayed in this way| The antigens, signal to other cells so they may either know what to look for or know to destroy the cells that these antigens are attached to.

2. Pathogens: AIDS/HIV
Type | Caused by the Human Immunodeficiency Virus | Methods of control| Reverse transcriptase inhibitors: These drugs inhibit the ability of the virus to make copies of itselfProtease inhibitors (PIs): These medications interrupt virus replication at a later step in its life cycle, preventing cells from producing new viruses.| Transmission| Through the exchange of body fluids, blood, semen, vaginal fluids, saliva (sexual transmission, blood products)| How it causes disease in the host| The HIV virus infects The cells disabling the normal immune process| Symptoms| pneumonia caused by Pneumocystis, which causes wheezing; brain infection with toxoplasmosis which can cause trouble thinking or symptoms that mimic a stroke; widespread infection with a bacteria called MAC (mycobacterium avium complex) which can cause fever and weight loss; yeast infection of the swallowing tube (esophagus) which causes pain with swallowing; widespread diseases with certain fungi like histoplasmosis, which can cause fever, cough, anemia, and other problems.|

3. Non- Specific Immune responses : Involves physical and chemical barriers, is not effected by any prior encounter with that agent, HAS NO “MEMORY” FOR FUTURE ENCOUNTERS
Skin| Intact skin acts as a barrier against entry by pathogens, Glands in the skin secrete fatty acids and sweat contains salt, Acids create pH range that is unsuitable for the growth of harmful microbes, Most bacteria cannot tolerate the salty conditions of the skin surface.| Natural Flora| Bacteria naturally live in body, inhabit the skin, the intestinal tract, These bacteria play a protective role against potentially harmful bacteria, Some members of natural flora opportunistic pathogens, sick injured rundown| Natural secretions | Tears and saliva contain enzymes that cause lysis of bacterial cells, Stomach acids kill harmful bacteria, Secretions also help flush away foreign particles| Mucous Membranes| Mucous secreted by the cells lining the respiratory tract help to trap bacteria, Cilia on these cells then sweep the foreign cells up to throat, swallow or cough it up, Mucous lining the digestive tract forms a protective barrier against penetration by microbes| Phagocytes| Type of white blood cell, Produced in the bone marrow, Engulf and destroy microbes and other foreign particles, name refers to ‘cells that eat’, includes macrophages and neutrophils| Natural Killer cells| Type of white blood cell, Kill virus-infected cells| Complement proteins | 20 different comp proteins, most made in liver, circulate blood stream, become active when infection occurs, help by 1) sticking to microbes to attract phagocytes 2) Coat bacteria so phagocytes ingest them easier, 3) some cause lysis of foreign cells| Interferon| Important group of...
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