B3- INFECTION AND RESPONSE Flashcards
What are pathogens?
Pathogens are microorganisms that cause infectious (communicable) diseases. They can infect plants or animals
How can pathogens spread?
- direct contact
- water or air
- vectors ( organisms that carry and pass on the pathogen without getting the disease
How can the spread of infectious diseases be reduced?
- simple hygiene measures ( washing hands etc)
- destroying vectors
- isolating infected individuals, so they cannot pass the pathogen on
- giving people at risk a vaccination
How do viruses cause damage to cells?
Viruses reproduce rapidly in body cells, causing damage to the cells
Key information about measles:
- the symptoms are fever and a red skin rash
- the measles virus is spread by breathing in droplets from sneezes and coughs
- most people recover well from measles, however it can be fatal if there are complications, so most young children are vaccinated against measles
What does HIV stand for?
Human immunodeficiency virus
Key information about HIV:
- causes AIDS
- spread by sexual contact or exchange of bodily fluids (can be transmitted in blood when drug users share needles)
- at first, HIV causes a flu-like illness
- if untreated, the virus enters the lymph nodes and attacks the body’’s immune system
- taking antiviral drugs can delay this happening
- late stage HIV, or AIDS, is when the body’s immune system cannot fight off other infections or cancers
What can bacteria do to cells and tissues?
Bacteria may damage cells directly or produce toxins (poisons) that damage tissues
Key information about Salmonella:
- Salmonella is a type of food poisoning caused by bacteria
- The bacteria are ingested in food, which may not have been cooked properly or may not have been prepared in hygienic conditions
- the bacteria secretes toxins, which cause fever, abdominal cramps, vomiting and diarrhoea
- chicken and eggs can contain the bacteria, so chickens in the UK are vaccinated against Salmonella to control the spread
Key information about Gonorrhoea:
- it is an STD caused by bacteria, which is spread by sexual contact
- the symptoms are a thick, yellow or green discharge from the vagina or penis and pain when urinating
- used to be easily treated by penicillin, but many resistant strains have now appeared
- the use of a barrier method of contraception can stop the bacteria being passed on
What are protists?
Protists are single-celled organisms
What is the difference between protists and bacteria?
Protists are eukaryotic cells and bacteria are prokaryotic cells
Key information about malaria:
- caused by a protist
- the protist uses a particular type of mosquito as a vector
- passed on to a person when they are bitten by the mosquito
- causes severe fever, which reoccurs and can be fatal
- one of the main ways to stop the spread is to stop people being bitten (killing the mosquitos or using mosquito nets)
Key information about the Rose black spot:
-it is a 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 early
- the loss of leaves will stunt the growth of the plant because photosynthesis is reduced
- can be treated using fungicides and removing and destroying the affected leaves
What are non-specific defences?
They are defences that work against all pathogens, to try and stop them entering the body
What do tears do?
Enzymes in tears destroy microorganisms
What does the cilia do?
Cilia create a wave motion, which sweeps mucus along
What do the glands in the stomach wall do?
Glands produce hydrochloric acid, which kills bacteria in food
What does the nose do?
The nose traps particles that may contain pathogens
What do the sebaceous glands do?
Sebaceous gland produces sebum, which kills bacteria and fungi
What happens when a pathogen enters the body?
The immune system tries to destroy it.
How do white blood cells help to defend against pathogens?
- phagocytosis, which involves the pathogen being surrounded, engulfed and digested
- the production of special protein molecules called antibodies, which attach to the antigen molecules on the pathogen
- the production of antitoxins, which are chemicals that neutralise the poisonous effects of the toxins
How does the body become immune to a pathogen?
If the same pathogen re-enters the body, the white blood cells respond more quickly to produce the correct antibodies. This quick response prevents the person from getting ill and is called immunity
What do vaccinations do?
- When a person has a vaccination, small quantities of dead or inactive forms of a pathogen are injected into the body.
- Vaccination stimulates the white blood cells to produce antibodies and to develop immunity
What happens if a large proportion can be made immune to a pathogen?
The pathogen will not be able to spread very easily
Antibodies are ——————-particular———-
Antibodies are specific to a particular pathogen
What can antibiotics do?
Antibiotics are medicines that kill bacteria inside the body. However, they cannot destroy viruses.
What are bacteria strains becoming resistant to?
Antibiotics
What is MRSA?
A strain of bacteria that is resistant to antibiotics
How can doctors reduce the rate at which resistant strains of bacteria develop?
- doctors should not prescribe antibiotics unless they are really needed, for non-serious infections or for viral infections
- patients must complete their course of antibiotics so that all bacteria are killed and none survive to form resistant strains
Why is there a constant demand to produce new drugs?
- new painkillers are developed to treat symptoms of disease, but do not kill the pathogens
- antiviral drugs are needed that will kill viruses without also damaging the body’s tissues
- new antibiotics are needed as resistant strains of bacteria develop
Where were drugs originally extracted from?
Plants and microorganisms
Where does digitalis originate from?
A heart drug which originates from foxgloves
Where does Aspirin originate from?
A pain killer that originates from willow
Where does penicillin originate from?
Discovered by Alexander Fleming from the Penicillium mould
How are most new drugs made?
Most new drugs are synthesised by chemists in the pharmaceutical industry. However, the starting point may still be a chemical extracted from a plant. New medical drugs have to be tested and trialled before being used to make sure they are safe (not toxic)
After drugs are found to be safe, why is it tested on patients?
- see if it works
- find out the optimum dose
How are tests usually done on patients?
Double-blind trials
What is the purpose of double-blind trials?
To ensure the test is completely fair. If the patients or doctors knew whether it was the drug or a placebo being used, it might influence the outcome of the test
How are double-blind trials done?
- some patients are given a placebo, which does not contain the drug, and some patients are given the drug
- patients are allocated randomly to the two groups
- neither the doctor or the patients know who has received a placebo and who has received the drug
What are new painkillers developed to do?
Treat the symptoms of disease- they do not kill the pathogens
How are monoclonal antibodies produced?
They are produced from a single cell that has divided to make many cloned copies of itself. They are produced by combining mouse cells with tumour cells to make a cell called a hybridoma.
What do monoclonal antibodies do?
They bind to only one type of antigen, so the can be used to target specific chemical or specific cells in the body
In which ways can monoclonal antibodies be used?
- in pregnancy tests, to bind the hormone HCG found in urine during early pregnancy
- in laboratories, to measure the levels of hormones and other chemicals in the blood, or to detect pathogens
- in research, to locate or identify specific molecules in a cell or tissue by binding them with fluorescent dye
- to treat some diseases (e.g. in cancer, they can be used to deliver radioactive substance, a toxic drug, or a chemical that stops cells dividing, specifically to the cancer cells)
Why are monoclonal antibodies not widely used yet?
They have created more side effects than expected
What are signs that a plant is diseased?
- stunted growth
- spots on leaves
- areas of decay (rot)
- growths
- malformed (abnormal) stems or leaves
- discolouration
- the presence of pests
How do you identify disease in plants?
- consulting a gardening manual or website
- taking infected plants to laboratory to identify the pathogen
- using testing kits, which contain monoclonal antibodies
What can plants be infected by?
Viral, bacterial and fungal pathogens, as well as by insects
Key information about tobacco mosaic virus (TMV) :
- widespread plant pathogen
- infects tobacco plants and many other plants, including tomatoes
- it produces a distinctive ‘mosaic’ pattern of discolouration on the leaves, which reduces chlorophyll content and affects photosynthesis
What are aphids?
Small insects often known as greenfly or blackfly. They feed from the phloem, taking sugars away from the plant
What do non-communicable diseases in plants include a range of?
Deficiency diseases, caused by a lack of mineral ions in the soil
Examples of deficiency diseases in plants:
- stunted growth is caused by nitrate deficiency, because nitrates are needed for protein synthesis
- chlorosis is caused by magnesium deficiency, because magnesium ions are needed to make chlorophyll
What physical defences do plants have to try and stop organisms entering them?
- cellulose cell walls
- a tough waxy cuticle on leaves
- layers of dead cells around stems (bark on trees), which fall off and take pathogens with them
What chemical defences do plants have to try and stop organisms entering them?
- antibacterial chemicals, which are made by plants such as mint and witch hazel
- poisons to deter herbivores, which are made by plants such as tobacco, foxgloves and deadly nightshade
What mechanical adaptations do plants have to try and stop organisms entering them?
- 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 the leaves, e.g. the white deadnettle does not sting, but looks very similar to a stinging nettle
