Infection and response Flashcards
What is a pathogen?
Pathogens are microorganisms that cause infectious diseases.
How can pathogens be spread?
They can be spread by:
-direct contact
-water or air
- Vectors (organisms that carry and pass on the pathogen without getting the disease.)
How you can prevent the spread of infectious diseases?
-washing hands
-destroying vectors
- isolating infected individuals so they cannot pass on the pathogen
-Taking a vaccination.
Measles.
-Disease caused by a virus
- Symptoms are fever and red skin rash.
-Spread by breathing in droplets from sneezes/coughs.
-Vaccinations are available.
HIV (human immunodeficiency virus)
-Spread by sexual contact or exchange of bodily fluids eg needles.
-Can cause a flu-like illness.
-If untreated the virus enters the lymph nodes and attacks the body’s immune cells.
-Taking antiviral drugs can delay this happening.
-Late stage HIV or AIDS is when the body’s immune system is damaged and cannot fight off infections or cancers.
What do viruses do?
They reproduce rapidly in body cells, causing damage to the cells.
What do bacteria do?
They may damage cells directly or produce toxins (poisons) that damage tissues.
Salmonella.
Type of food poisoning caused by bacteria:
-Might have not been cooked properly or in hygienic conditions.
-Bacteria secrete toxins that can cause fever, abdominal cramps etc.
- Chickens are vaccinated to control the spread.
Gonorrhoea.
- Cause by bacteria.
-Spread by sexual contact. - Symptoms are a thick, yellow or green discharge from the vagina or penis and pain when urinating.
- Easily treated with penicillin but many resistant strains have now appeared.
-Use of a barrier method of contraception can stop the bacteria from being passed on.
What are protists?
They are single-celled organisms and are eukaryotic.
Malaria.
Caused by a protist.
- The protists use a particular type of mosquito as a vector.
- Passed on to a person when they are bitten.
- Causes severe fever.
-Prevention= Killing the mosquitoes or mosquito nets.
Rose black spot.
Fungal disease.
-spread when spores are carried from plant to plant by water or wind.
- Purple or black spots develop on leaves which often turn yellow and drop off.
- Loss of leaves stunt growth of the plant because photosynthesis is reduced.
-Can be treated by fungicides and removing the affected leaves.
What are the body’s defences?
Tears- enzymes in tears destroy microorganisms.
Nose- Traps particles that may contain pathogens.
Goblet cell- mucus traps particles and bacteria. Cilia create a wave motion that sweeps mucus along.
Glands in the stomach wall produce HCL which kills bacteria in food.
What is phagocytosis?
It is when the pathogen is surrounded and then engulfed and digested by a white blood cell.
What are the steps of phagocytosis?
1) Microorganisms invade the body.
2) The wbc finds the microorganisms and engulfs them.
3) The wbc ingests the microorganisms.
4) The microorganisms have been digested and destroyed.
What are the steps of making antibodies?
1) Antigens are markers on the surface of the microorganism.
2) The wbcs become sensitised to the antigens and produce antibodies.
3) The antibodies then lock onto the antigens.
4) This causes the microorganisms to clump together so that other wbcs can digest them.
What is immunity?
If the same pathogen comes again the wbcs response will be quicker to produce antibodies. This quick response prevents the person from getting ill and is called immunity.
What is a vaccination?
Small quantities of dead or inactive forms of a pathogen are injected into the body.
What does a vaccination do?
it stimulates the wbcs to produce antibodies and to devolp immunity.
What are antibiotics?
Antibiotics are medicines that kill bacteria inside the body but cannot destroy viruses.
What is MRSA?
It is a strain of bacteria that is resistant to antibiotics.
(RP) Investigating the effect of different antibiotics on bacterial growth.
1) Inoculate a petri dish with a culture of bacteria.
2) Soak small discs of filter paper in different antibiotics.
3) Using forceps, place the antibiotic discs on the surface of the agar.
4) Incubate the sealed dish upside down at 25 degrees for several days.
What are the variables for the RP Investigating the effect of different antibiotics on bacterial growth?
IV= The type of antibiotic.
DV= The area around each disc that is clear of bacteria.
CV= The concentration of antibiotic used and the length of time that the discs are soaked.
Why are new painkillers made?
To treat the symptoms of disease but they do not kill the pathogens.
What are antiviral drugs needed for?
They are needed to kill viruses without also damaging the body’s tissue.
What are new antibiotics needed for?
They are needed as resistant strains of bacteria develop.
What is Digitalis?
It is a heart drug that originates from foxgloves.
What is Aspirin?
It is a pain killer that originates from willow.
Who discovered Penicillin?
Alexander Fleming from the penicillium mould.
How does a double-blind trial work?
-Some patients are given a placebo that does not contain the drug and some patients get the drug.
-Patients are allocated randomly to the two groups.
-Neither the doctors nor the patients know who has received a placebo and who has received the drug.
What are double-blind trials used for?
Once the drug is found to be safe it is then tested on the patients to see if it works and find out the optimum dose.
Monoclonal Antibodies
-They are produced from a single cell that has divided to make many cloned copies.
-Only bind to one specific antigen to target a specific chemical or cell.
-produced by combining mouse cells and a tumour cell to make a hybridoma.
How can monoclonal antibodies be used?
-In pregnancy tests to bind to the hormone HCG found in urine during pregnancy.
- In laboratories to measure the levels of hormones.
-To treat diseases.
Why are monoclonal antibodies not used widely yet?
Because they have created more side effects then expected.
What are some signs that a plant may have a disease?
-Stunted growth
-Spots on leaves
-Rot
-Growths
How do you identify a disease in a plant?
-Consulting a gardening manual or website
-Taking infected plants to a laboratory to identify the pathogen.
-Using testing kits, which contain monoclonal antibodies.
Tobacco mosaic virus (TMV)
-Widespread plant pathogen.
-Produces a mosaic pattern of discolouration on the leaves, which reduces chlorophyll and affects photosynthesis.
- Affects growth due to lack of photosynthesis.
What are Aphids?
They are small insects often known as green or black flies. They feed from the phloem taking sugars away from the plant.
What is stunted growth caused by?
It is caused by nitrate deficiency because nitrates are needed for protein synthesis.
What is chlorosis caused by ?
It is caused by magnesium deficiency because magnesium ions are needed to make chlorophyll.
What are the plants physical defences?
-Cellulose cell walls
-a tough waxy cuticle on leaves
-layers of dead cells around stems that fall off and take pathogens with them.
What are the plant’s chemicals defences?
-Antibacterial chemicals, which are made by plants such as mint and witch hazel.
-Poisons to deter herbivores. Made by tobacco, foxgloves and deadly nightshade plants.
What are the mechanical adaptations of a plant?
-Thorns and hairs to deter animals from eating or touching them.
-leaves that droop or curl when touched.
-mimicry to trick animals into not eating them or not laying eggs on them.
