what is an infectious disease?
Disease caused by a pathogen that passes from infected individuals to uninfected individuals
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| Term | Definition |
|---|---|
| what is an infectious disease? | Disease caused by a pathogen that passes from infected individuals to uninfected individuals |
| what is a non infectious disease ? | Long-term diseases that are not caused by pathogens |
| what are the 4 types of pathogens ? | Bacteria Viruses Fungi Protists |
| what methods can be used to prevent the spread of pathogens? | Hygienic food preparation Personal hygiene Waste disposal Sanitation |
| what are the symptoms of measles | - The main symptoms of measles are fever and a red skin rash. - Most people recover well from measles; however, it is a serious disease that can cause blindness and brain damage. |
| how is measles spread? | - The virus is spread by inhaling droplets from coughs and sneezes. |
| treatment and prevention of measles | - There is no treatment for measles, so anyone who becomes infected needs to be isolated to stop the spread of the virus. - Measles is now greatly reduced in the UK due to improved living conditions and a vaccination programme for young children. |
| hiv symptoms | -starts with a flu like illness - if untreated it can travel to the lymph nodes and attack cells of the immune system - can stay hidden in the immune system for many years until the body develops aids |
| how is hiv spread ? | - direct sexual contact - exchange of bodily fluids e.g. blood transferred between shared drug needles - from mother to child during birth or breast milk |
| treatment and prevention of hiv | - no cure - antiretroviral drugs used early in the infection can effectively control the disease to slow or halt the process to AIDS |
| tmv symptoms | - distinctive mosaic pattern of discolouration of the leaves as the virus infects chloroplasts - stunted growth due to lack of photosynthesis- reduced crop yield |
| how is tmv spread ? | - plants in direct contact with an infected plant - virus can stay in soil for a long time |
| treatment and prevention of tmv | - no treatment - to control it farmers should have good field hygiene - farmers use tmv resistant strains of crops |
| symptoms of salmonella | The symptoms of a Salmonella infection start between 8–72 hours of eating infected food - The bacteria secrete toxins that cause the body to react with; fever, abdominal cramps, vomiting and diarrhoea. These symptoms are the body trying to remove the infection from the gut - Generally the infection doesn’t last for more than a few days. It is more serious in young children and the elderly due to dehydration |
| how is salmonella spread ? | - Contaminated food that has not been cooked properly is the main cause of Salmonella food poisoning - It can be found in eggs and egg products that are not cooked such as mayonnaise |
| treatment and prevention of salmonella | Chickens in the UK are vaccinated against Salmonella - Proper hygiene in the kitchen: ° Preventing raw meat from contaminating cooked meat ° Cooking all food thoroughly, not washing raw meat (it spreads the bacteria around the kitchen) - Washing surfaces and hands before and after handling raw meat especially chicken |
| symptoms of gonorrhoea | - in early stages it includes , thick yellow or green discharge from vagina or penis when urinating - can cause infertility , ectopic pregnancies and pelvic pain - babies born to women with disease can get eye infections and be bor blind |
| how is gonorrhoea spread | - unprotected sexual contact |
| treatment and prevention of gonorrhoea | - barrier method of contraception like a condom - antibiotic treatment but now many strains have become resistant to them - tracing all sexual partners so all individuals can be testes and treated |
| symptoms of rose black spots | - purple or black spots on the leaves which can then turn yellow and drop off - loss of leaves means there is less chloroplasts for photosynthesis - reduction in photosynthesis means the plant has less energy to make flowers |
| how is rose black spots spread | - spores from the fungus are carried in the wind or water |
| treatment and prevention of rose black spots | - the plant can be treated with fungicide chemicals - the leaves can be removed and burned to prevent the spread of the infection over the plant - breeding of varieties of plants that have resistance to the disease |
| symptoms of malaria | - recurrent fever and shaking when protists are bursting out of the red blood cells - these episodes can weaken the host to a fatal extent |
| how is malaria spread? | - a female anopheles mosquito ( the vector ) bites a human - the malaria parasite infects the liver and reproduces asexually - malaria parasites is in the blood of humans - a mosquito consumes the infected blood when feeding - there is sexual reproduction of the malaria parasite - the process repeats |
| treatment and prevention of malaria | - if diagnosed early it can be treated with a combination of drugs - however the protists that cause malaria have become resistant to most drugs - spread can be reduced by controlling mosquito populations by : - using insecticides in buildings - using insecticide coated nets to kill mosquitos and prevent them biting - preventing mosquitos from breeding by spraying to kill the larvae or removing standing water sources |
| biological defences the body has against pathogens | - hair and mucus in nose to trap pathogens - enzymes in most tears , nasal secretions and saliva - sebaceous gland produces sebum which kills bacteria and fungi |
| chemical defences in body from pathogens | - glands in stomach produce hydrochloric acid in the lining - goblet cells produce mucus |
| physical defences in the body from pathogens | -cilia lined trachea - ciliated epithelial cells - the skin |
| phagocytosis | Phagocytes engulf and digest pathogens, this can be non-specific or helped by antibodies which cause agglutination (clumping) of pathogens The phagocyte surrounds the pathogen and releases enzymes to digest and break it down to destroy it |
| Production of antibodies | - a pathogen enters the body - a lymphocyte detects this and releases antibodies - antibodies have a complementary shape to the antigen on a pathogen - each lymphocyte in the body produces one type of anybody |
| what are memory cells | Memory cells are lymphocytes that remain in the body after an initial infection with a particular pathogen they produce the specific antibodies against its antigens so that if you get infected by the same pathogen again in the future (and the antigens are the same) you can produce antibodies much quicker |
| how are antitoxins produced | -antitoxin molecules bind to toxin and neutralises it |
| how do vaccines work | - a dead or inactive pathogen is injected into the body - antigens trigger an immune response - lymphocytes are able to produce complementary antibody multiples which are released - memory cells are produced . if the antigen is encountered again antibodies are produced must faster - this equals to long term immunity |
| how do some bacteria become resistant to antibiotics ? | - there is a population of bacteria in the gut . some have antibiotic resistance - when exposed to an antibiotic , bacteria causing an illness, as well as healthy gut bacteria are killed - with reduced competition for nutrients , antibiotic nutrients , antibiotic bacteria multiply forming a larger population that is difficult to control |
| how do doctors prevent antibiotic resisitance | Doctors need to avoid the overuse of antibiotics, prescribing them only when needed – they may test the bacteria first to make sure that they prescribe the correct antibiotic Antibiotics shouldn't be used in non-serious infections that the immune system will ‘clear up’ Antibiotics shouldn't be used for viral infections Patients need to finish the whole course of antibiotics so that all the bacteria are killed and none are left to mutate to resistant strains Antibiotics use should be reduced in industries such as agriculture – controls are now in place to limit their use in farming |
| who discovered penicillin from mould | Alexander Fleming |
| what drug does foxglove produce and what does it treat ? | digitalis helps strengthen the heart beat |
| what drug does willow bark produce and what does it treat ? | aspirin painkiller, fever, inflammation |
| what are new drugs tested for | Toxicity – does it have harmful side effects? Efficacy – does the drug work? Dose – what dose is the lowest that can be used and still have an effect? |
| what are the 3 stages of drug development ? | - preclinical testing - whole organism testing - clinical trials |
| describe preclinical testing | The drug is tested on cells in the lab Computer models may also be used to simulate the metabolic pathways that may be taken by the drug Efficacy and toxicity are tested at this stage |
| describe whole organism testing | The drug is tested on animals to see the effect in a whole organism – all new medicines in the UK have to have tests on 2 different animals by law Efficacy, toxicity and dosage are tested at this stage |
| describe clinical trials | The drug is tested on human volunteers first, generally with a very low dose then increased. This is to make sure it is safe in a body that is working normally The next stage is to test on patients with the condition. The patients are often split into two groups; one given the drug the other given a placebo. This is called a double-blind study – neither the doctor nor the patient knows if the patient is getting the placebo or the active drug Once the drug is found to be safe then the lowest effective dose is tested at this stage |
| what are monoclonal antibodies | Monoclonal antibodies are antibodies that are made by identical immune cells, these identical immune cells are clones of the parent cell |
| how are monoclonal antibodies produced ? | - an antigen is injected into a mouse - the mouse produces a lymphocyte with an antibody complementary to the antigen - this lymphocyte is fused with a tumour cell - a hybridoma cell is produced - the hybridoma clones - there is now an endless supply of monoclonal antibodies |
| how are monoclonal antibodies used in pregnancy tests ? | - Pregnancy tests detect the hormone hCG, which is only present in the urine of pregnant people. - The test strip contains monoclonal antibodies that are specific to hCG. - In the first part of the strip, mobile antibodies with a coloured dye attach to any hCG in the urine. - The urine carries these antibody–hCG complexes along the strip by capillary action. - At the test line, there are immobilised antibodies that also bind to hCG. - If hCG is present, the complex gets trapped here and forms a coloured line. - Further along is the control line, which contains immobilised antibodies that bind to the mobile antibodies whether hCG is present or not. - The control line shows the test has worked properly. |
| how are monoclonal antibodies used in diagnosis of disease ? | the monoclonal antibodies are specific to antigens found on the surface o pathogens , blood clots or cancer cells, they also contain markers that help doctors to find the location of them |
| how are monoclonal antibodies used in research? | monoclonal antibodies with a fluorescent dye attached can be used by scientists to discover molecules in a cell or tissue |
| how are monoclonal antibodies used in treating disease? | many types of cancer are difficult to treat. monoclonal antibodies can be used in three ways to treat cancer: - use of the monoclonal antibodies to trigger immune cells to destroy them - using monoclonal antibodies to block receptors, which stops them growing and dividing - carry toxic drugs, or radioactive substances for radiotherapy, to the site of the tumour |
| advantages of monoclonal anitbodies ? | - they only bind to specific molecules on diseased or damaged cell - do not affect healthy cells - highly specific so can be produced to treat a range of conditions - hoped to be a cheaper procedure and a tried and tested method of treatment |
| diadvantages of monoclonal anitbodies ? | caused more side effects than first expected. the use of mice antibodies caused complications. now humanised antibodies are being developed • it is an expensive process at the moment • producing specific monoclonal antibodies is proving to be more difficult than expected |
| how can aphids infest plant ? | Aphids have long sharp mouthpieces that pierce the surface of the stem and into the phloem so that they can feed on the sugar filled sap They can infest a plant in large numbers and remove large quantities of the phloem sap. This can weaken the plant Aphids can also act as a vector for the transfer of diseases Biological pest control (using ladybirds, a natural predator of the aphid) to feed on them or using chemical pesticides are the best ways to control infestation with aphids |
| what are nitrates used for in plants and what happens when deficient? | - Production of amino acids for proteins. - Stunted growth, upper leaves pale green and lower leaves yellow and dead. |
| what are magnesium used for in plants and what happens when deficient? | - Synthesis of chlorophyll. Chlorophyll is needed for photosynthesis. - Yellowing leaves (chlorosis), due to less chlorophyll and stunted growth. |
| what are potassium used for in plants and what happens when deficient? | - Production of flowers and fruit - Poor growth of flowers and fruit, yellow leaves and dead spots. If you want them turned into revision cards or simplified notes, I can do that too. |
| plant physical defences | The cellulose cell wall not only provides support for the plant but also protection from microorganisms The waxy cuticle of the leaf is a barrier to microbes from entering the plant. The only place that they can enter in the leaf is through the stomata Bark provides a tough layer around the stem of the plant to prevent pathogens from entering As deciduous trees lose leaves in the winter the infection can be taken with them |
| plant chemical defences | Many plants produce chemicals that have antimicrobial properties Many herbal face creams can use plant extracts such as tea tree oil, mint and witch hazel to have an antibacterial effect More plants are being studied for their potential source of antibiotics as more strains are becoming resistant to current antibiotics |
| how does poison work in plants defence | - Some plants produce poisons to deter herbivores from eating them. Animals will quickly learn to avoid eating plants that make them feel unwell. |
| how does thorns work in plants defence | - Make it unpleasant or painful for large herbivores to eat them. |
| how do hairy stems work in plants defence | Hairy stems or leaves deter insects and larger animals from feeding on them or laying eggs on the stem or leaves. |
| how does drooping or curling when touched work in defence | - This is a rare but effective mechanism, when touched the leaves will automatically curl which can dislodge insects and frighten off larger species. |
| how does mimicry when touched work in defence | - Plants can droop to look as though they are diseased and trick animals into not eating them. They can also resemble larger insects to scare away any potential threats. |