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| Question | Answer |
| The microorganisms which cause diseases are called PATHOGENS. Once BACTERIA and VIRUSES get inside your body they REPRODUCE RAPIDLY. | They damage your tissues and may produce toxins (which cause the symptoms of the disease) A disease caused by bacteria - food poisoning. A disease caused by viruses - chicken pox |
| How are pathogens spread? | Droplet (in the air), e.g. TB Direct contact (skin to skin). Through cuts/piercings in the skin, e.g. tetanus. Contaminated food or drink, e.g. salmonella. |
| Defense mechanisms | The skin. Cilia and mucus in breathing system. Clotting of the blood. Acid in the stomach. White blood cells (antibodies and antitoxins). Tears (make an antiseptic liquid). |
| Painkillers: help to relieve the symptoms of an infectious disease but do not kill the pathogens. Antibiotics: only work on bacteria by destroying their cell walls (viruses live inside our cells). | Kill infectious bacteria in the body using specific antibiotics for specific bacteria. Don't work out of date. Overuse & inappropriate use has caused some bacteria to become resistant to antibiotics. |
| Mutation: MRSA - 1000 deaths a year UK When bacteria reproduce their DNA is made very quickly causing mistakes and mutations that can give them resistance to a certain antibiotic. The immune system can deal with resistant and non resistant bacteria alike. | This antibiotic will be given and kill most of the bacteria but the resistant will survive, reproduce and pass on the resistance to the antibiotic. Mutation may occur again making these bacteria resistant to several main antibiotics which is difficult to control. |
| Steps to reducing this problem. | Only use antibiotics when really needed. Staff wash hands/alcohol gel between patients. Visitors wash hands when coming into hospitals. Patients with antibiotic resistant bacteria should be kept in isolation. |
| Epidemic: More cases than would normally be expected. Pandemic: Much larger/worldwide scale e.g. bird flu. | Why more common than before? People travel more often and easily. Pathogens are mutating more and becoming resistant to antibiotics due to overuse. |
| White blood cells: Phagocytes: lobed nucleus, ingest/engulf and destroy pathogens. Lymphocytes: large nucleus, produces antibodies and antitoxins. | Antibodies target particular bacteria or viruses and destroy them. Need a unique antibody for each antigen/pathogen. |
| Antigens are the chemical on the surface of a pathogen that stimulates an immune response. Antibodies attach to these ready for the phagocytes to destroy. Antitoxins counteract the toxins released by the pathogens. | Memory cells remember dealing with the pathogen before and producing the specific antibody, so these can be produced very quickly if the same pathogen gets into the body again. This is called NATURAL IMMUNITY. |
| VACCINATIONS = ACQUIRED IMMUNITY. Made from a dead or inactive form of the disease causing pathogen OR the antigens. This triggers your natural immune response. | Memory cells are made which means more antibodies faster if exposed to a real pathogen (and stay in the body for longer). If a large proportion of the population is vaccinated, the spread of the pathogen is reduced. |
| Louis Pasteur, 1850s: It was thought that life originated from non-living forms of matter - SPONTANEOUS GENERATION. 'Swan-necked flask' with sterile broth, bacteria was trapped in the bend, neck was broken and bacteria got in. | Ignaz Semmelweis noticed that many women died of 'childbed fever' after childbirth. Recognised the importance of hand washing between patients but this was ignored until after his death. Greatly reduced number of deaths in hospitals. |
| Alexander Fleming accidentally discovered a fungus (penicillium) growing on an old bacterial plate which had killed all the bacteria around it. The first antibiotic - penicillin. | Problems with developing new antibiotics: Long process of drug testing. Costs a lot of money. Bacteria could mutate by the time the drug is licensed. |
| Agar Plates and Aseptic Techniques: Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics. Wash hands & swab bench with disinfectant. Heat inoculating loop & neck of bottle to sterilize. Open lid of agar plate slightly & for a short amount of time - reduce air contamination. | Don't seal all the way round so oxygen can get in to reproduce & anaerobic bacteria can't grow. Store at 25oC not 37oC so pathogens that are harmful to us can't grow. Store upside down so when they respire the condensation won't collect and fall onto the bacteria. |
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