Infection and response (P1): Biology AQA GCSE

viruses, bacteria, protists, fungi

by direct contact, water or air

microorganisms that cause infectious disease

bacteria and viruses

poisons (toxins) that damage tissues + make us feel ill

live and reproduce inside cells (replicate themselves using cells’ machinery producing many copies of themselves, cells then bursts releasing all new viruses) causing cells damage

measles, HIV, Tobacco

rose black spot

malaria

inhalation of droplets from sneezes + coughs

sexual contact/ exchange of bodily fluids (eg blood when drug users share needles)

fever, red skin rash

vaccination at young age

cause serious illness, can be fatal if complications arise (eg pneumonia (a lung infection) or inflamation of the brain

unless successfully controlled the virus attacks body’s immune cells, late stage infection (AIDS) occurs when body’s immune system is so badly damaged it can no longer deal with other infections or cancers

initial flu-like illness, no symtoms for several years

antiretrovial drugs which stops virus from replicating in body

Many species of plants, including tomatoes

Distinctive mosaic pattern of discolouration on leaves

Affect growth of plant due to lack of photosynthesis (Discolouration on leaves)

bacteria ingested in food or on food prepared in unhygienic conditions

Poultry vaccinations

Fever, abdominal cramps, vomiting, and diarrhoea

Secrete toxins

Sexual contact (STD)

Thick yellow or green discharge from the vagina or penis, pain and urinating

-was easily treated with antibiotic penicillin until many resistant strains appeared
-Controlled by treatment with antibiotics or use of barrier method of contraception e.g. condom

Purple or black spots develop on leaves often turning yellow and dropping early

Affects the growth as photosynthesis is reduced due to leaf discolouration

In the environment by water or wind

Using fungicides and/or removing and destroying the effected leaves

Recurrent episodes of fever and can be fatal

The mosquito

By its vectors, Mosquitoes

By preventing vectors (Mosquito) From breeding and by using mosquito nets to avoid being bitten

The immune system tries to destroy the pathogen

-phagocytosis (engulfing foreign cells and digesting them)
-antibody production (antibodies specific to type of antigen on invading pathogen, Antibodies lock onto invading cells so that they are found and destroyed by other white blood cells)
-antitoxin production (Counteract toxins produced by invading bacteria)

No

no , but used to treat symptoms of disease

Damaging the body’s tissues

Toxicity, efficacy, dose

-stunted growth
-Spots on leaves
-Areas of decay (rot)
-Growths
-Malformed stems or leaves
-discolouration
-Presence of pest

-reference to a gardening manual or website
-Taking infected plants to laboratory to identify pathogen
-Using testing kits that contain monoclonal antibodies

Act as a barrier to pathogens and secretes antimicrobial substances which kill pathogens

Has a mucus in your nose trap particles that could contain pathogens

-secrete mucus to trap pathogens
-lined with cilia (hair like sructures) which wafts the mucus up to the back of the throat where it can be swallowed

Produces hydrochloric acid which kills pathogens that make it that far from the mouth

Destroys/fights pathogens that make it into your body

-being hygienic (E.g. washing hands before preparing food or after you sneezed)
-Destroying vectors (Killed using insecticides or destroying their habitats)
-isolating infected individuals (Prevent spread)
-Vaccination (Less likely to develop infection and pass it on)

Small quantities of dead or inactive forms of a pathogen

-inject/introduce small quantities of dead or inactive forms of a pathogen into body
-Stimulates white blood cells to produce antibodies
-If pathogen enters white blood cells respond quickly to produce the correct antibodies (learnt from before) preventing infection

-helped control lots of communicable diseases that were once common e.g. smallpox
-Epidemic can be prevented if large percentage of population is vaccinated (Even the people who aren’t vaccinated unlikely to catch disease because fewer people are able to spread it)

-vaccines don’t always work and might not give immunity
-sometimes have bad reaction to vaccine (but very rare)

Penicillin

Medicine that help cure bacterial diseases by killing infective bacteria inside body

Greatly reduced deaths from infectious bacterial diseases

Emergence of strains resistant to antibodies is increasing (caused by over prescribing and use)

Extracted from plants and microorganisms

Foxgloves

Willow

Penicillium mould discovered by Alexander Fleming

Synthesized by chemists in the pharmaceutical industry (however starting point may still be chemical extracted from plant)

tested and trialled

In a laboratory using cells tissues and live animals

Healthy volunteers and then patients

- very low doses of drug given at start
- if drug is safe further clinical trials carried out to find optimum dose
-double blind trials

Where some patients are given a placebo

Scrutiny by peer review

lots of clones of a single WBC (meaning all antibodies are identical and will only target one specific protein antigen)

1. Preclinical testing: drugs tested on human cells and tissues in lab
2. preclinical testing: drugs tested on live animals
3. Clinical trial: drug tested on human volunteers (first healthy volunteers, then patients in a double blind trial)

So able to target specific chemical or specific cells in body

Identical antibodies

1. Mouse lymphocytes stimulated to make particular antibody
2. Lymphocytes combined with particular kind of tumour cell to make a hybridoma cell
4. Hybridoma cell Can Divide and make the antibody so single hybridoma cells cloned to produce many identical cells that's all produce the same antibody
5. Large amount of antibody collected and purified

- diagnosis such as in pregnancy tests (hormone/chemical testing for binds to antibodies on coloured beads, getting stuck on a strip, showing the colour)
- in laboratories to measure the levels of hormones and other chemicals in blood or detect pathogens
- in research to locate or identify specific molecules in a cell or tissue by binding them with a fluorescent dye
- to treat some diseases: for cancer monoclonal antibody can be bound to Radioactive substance, a toxic drug or a chemical which stops cells growing and dividing and delivers substance to cancer cells without harming other cells and body

Animal cruelty

They create more side effects than expected

in cancer treatment does not affect normal body cells like other treatments as only target specific cells meaning the side effects are lower than other treatments

cause more side effects than originally expected (eg fever vomiting and low blood pressure), scientists thought due to specific target not a lot of side effects

Range of viral, bacterial and fungal pathogens as well as insects

Nitrates are needed for protein synthesis and therefore growth so a lack of nitrates causes stunted growth

Magnesium ions needed for making chlorophyll which is needed for photosynthesis, plants without enough magnesium suffer from chlorosis and have yellow leaves

The ability to provide optimum conditions for plants through the understanding

Poor/distorted growth, sticky honeydew and sooty moulds

pesticides

- cellulose cell walls
- tough waxy cuticle on leaves
- layers of dead cells around stems (bark on trees) which fall off

- antibacterial chemicals which kill bacteria (eg mint and witch hazel)
- poisons to deter herbivores (eg tobacco plants fox gloves and deadly nightshade)

- thorns and hairs to deter animals
- leaves which droop or curl one touched (preventing themselves from being eaten by knocking insects off and moving away from things)
- mimicry to trick animals (eg the passion flower has bright yellow spots which looks like butterfly eggs stopping butterflies laying eggs there)