b3

pathogens

microorganisms that cause infectious disease

types of pathogen

bacteria, virus, fungi, protists

bacterial pathogens

reproduce quickly in the body and produce toxins that damage tissue

viral pathogens

infect and reproduce themselves inside body cells, causing damage to the cells

human defence systems

nose, stomach, skin, trachea, bronchi, white blood cells

defences in the nose

hair and mucus trap microbes

defences in the stomach

hydrochloric acid in the stomach kills microbes

defences in the skin

physical barrier against microbes

defences in the trachea

cilia and mucus trap microbes, and the cilia moves the microbes up and out of the body

phagocytosis

white blood cell engulfs or ingests, then digests a pathogen

antibodies

produced by a white blood cell, attach to antigens on a microbe surface to help kill it

antitoxins

produce by white blood cells to counteract toxins produced by pathogens

process of vaccination

dead or weakened inactive form of the pathogen is injected into the body, white blood cells are stimulated to produce antibodies against the pathogen, memory cells stay in the body so on reinfection antibodies are made quickly and in large numbers, pathogen is quickly killed/destroyed

salmonella food poisoning

bacterium disease, spread by eating infected food. causes fever, abdominal cramps, vomiting and diarrhoea. prevent by vaccinating poultry and basic hygiene especially when preparing food

gonorrhoea

bacterium disease, spread by sexual contact. causes thick yellow or green discharge from vagina/penis and pain on urinating. treated with antibiotics and prevented by barrier methods

measles

viral disease, spread by inhaling droplets from sneezes or coughs. causes fever and red skin rashes, can be fatal if complications arise. prevent by vaccinating young children

HIV

viral disease, spread by sexual contact or exchange of bodily fluids eg drug users sharing needles. causes flu-like illness initially, later on the virus attacks the body’s immune system(white blood cells), progressing to AIDS where the body cannot fight infections. can be controlled with antiretroviral drugs, prevented by condoms, not sharing needles

tobacco mosaic virus

viral disease spread by contact between infected plants. causes mosaic pattern of discolouration on leaves, therefore less photosynthesis, less sugars produced and less growth. treat by removing and destroying (preferably burning) infected plants.

rose black spot

fungal disease spread by wind or water carrying spores. causes purple or black spots on leaves which turn yellow and drop early, less photosynthesis, less sugars produced, less growth. treat by removing and destroying infected plants or using a fungicide

malaria

protist disease, spread by vectors (mosquitoes). causes recurring fever, fatal in extreme circumstances. prevent by using mosquito nets or preventing the breeding of mosquitoes

antibiotics

kill bacterial pathogens. specific antibiotics kill specific pathogens, cannot kill viral pathogens

why is it difficult to develop drugs that kills viruses?

viruses infect and reproduce themselves within body cells, it is very hard to develop drugs that do not damage the body’s cells or tissue

painkillers

treat the symptoms of an illness. do not kill pathogens

what produces digitalis (heart drug)

foxgloves

what produces aspirin

willow

what produces penicillin

penicillium mould discovered by alexander fleming

what are new drugs tested for?

toxicity, efficacy, dosage

first step of drug testing

chemicals are made by chemists or extracted from plants for the possible drugs

second step of clinical testing

pre-clinical trials, the drug is tested on cells, tissues or animals in the lab (testing for toxicity)

third step in drug testing

clinical trials, done on healthy volunteers to test for side effects. very low doses are given, then trials for optimum dose if safe. double blind trials test for efficacy.

double blind trials

some volunteers are given treatment with the drug, others are given a placebo (treatment that is identical but doesn’t contain the drug). nobody knows who has taken the drug and who hasn’t, and efficacy is shown once it is revealed who has taken the drug and who hasn’t

peer review

fellow scientists examining the results to prevent false claims and bias

zero error

when a measuring instrument gives a non-zero reading when the true value being measured is actually zero

monoclonal antibodies

antibodies produced from a single clone of cells. they are specific to one protein antigen

producing monoclonal antibodies using mice

mouse is injected with the protein antigen that we want the antibodies for. it’s lymphocytes produce the antibody for the antigen however this cannot divide indefinitely. fusing the lymphocyte with a tumour cell creates a hydridoma, which both produces the antibody and divides indefinitely through being cloned, making large quantities of the antibody

monoclonal antibodies in pregnancy tests

pregnancy tests: during early pregnancy hCG is present in urine. fixed antibodies can detect hCG. urine is applied to the bottom of the test strip, it soaks up the test strip and meets the antibodies. if hCG is present, it attaches to the antibody and causes a colour change. a control line ensures the test is done properly.

using monoclonal antibodies to detect pathogens/hormones/other chemicals in the blood

done in a lab. if the pathogen is present, it will attach to the monoclonal antibodies, causing a colour change in the sample. same goes for the hormones and chemicals, just with specific antibodies

using monoclonal antibodies to locate certain molecules in cells/tissue

attach a fluorescent dye molecule to the back of a monoclonal antibody. these can attach to the specific molecules in the body and the fluorescence will show under a microscope

using monoclonal antibodies to treat cancer

monoclonal antibodies have a drug attached to them. the antibodies attach to the cancer cells, delivering the drug and destroying the cancer cells. healthy cells are not effected, allowing lower dosages to be used for fewer side effects

disadvantages of monoclonal antibodies

create more side effects than expected, ethical issues

indicators of plant disease

spots on leaves, discolouration of leaves, growths, malformed stems or leaves, stunted growth, areas of decay, presence of pests

identifying plant diseases

refer to a garden manual or website, taking the infected plant to a laboratory to identify the pathogen, using a testing kit that contains monoclonal antibodies

nitrate deficiency

leads to stunted growth as nitrates are needed to make amino acids, which make proteins for growth (protein synthesis)

magnesium deficiency

leads to chlorosis (lack of chlorophyll). magnesium ions are need to make chlorophyll, a lack leads to less photosynthesis, less production of glucose

physical plant defence responses

layers of dead cells around stems which fall off taking microbes with it, eg bark on trees. waxy cuticles on leaves , a tough layer protecting from invasions. cellulose cell walls

chemical plant defence responses

making antibacterial chemicals, poisons in plant tissue/berries to deter herbivores

mechanical plant defence responses

thorns and hairs to deter animals, leaves which droop or curl up when touched, mimicry to trick animals