GCSE Infection and response AQA

What is a pathogen?

A microorganism that causes infectous disease

Why do bacteria make you feel ill?

They produce toxins that damage your cells and tissues

How do viruses reproduce?

They infect living cells and replicate themselves

The cell will then burst releasing all the new viruses

The cell damage makes you feel ill

What are protists?

Single celled eukaryotes

Some are parasites which live on or inside other organisms causing damage

They are often transferred to the organism by a vector

What are fungi?

Some fungi are single celled

Others have a body which is made up of hyphae (thread like structures)

Hyphae can grow and penetrate human skin and the surface of plants causing disease

The hyphae can produce spores, which can be spread to other plants and animals

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How can pathogens be spread?

Water- drinking or bathing dirty water

Air - pathogens can be carried in the air then breathed in e.g droplets from cough or sneeze

Direct contact- Touching contaminated surfaces

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How is measles spread?

By droplets from an infected person's sneeze or cough

Symptoms of measles

Fever and a red skin rash

What can measles lead to?

Pneumonia or encephalitis

How to prevent measles

vaccination

How is HIV spread?

Sexual contact, or exchange of body fluids such as blood when drug users share needles.

Symptoms of HIV

flu like symptoms however doesn't experience symptoms for several years

What does HIV do, and what does it lead to?

Attacks immune cells and damages the immune system , White blood cells cant cope with other infections or cancers at this stage it is AIDS

How to stop the spread of HIV

Use contraception e.g condoms

Don't share needles

Once infected use antiretoviral drugs, these stop the virus replicating in the body

What is TMV

Tobbaco mosaic virus is a virus that affects many species of plants e.g tomatoes

It causes a mosaic pattern on the leaves of plants - parts become discoloured

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What does TMV mean for plants?

Discolouration means the plants can't photosynthesise so the virus affects growth

What is rose black spot?

A fungus that causes purple or black spots to develop on the leaves of rose plants plants. The leaves turn yellow and drop off

What does rose black spot mean for plants?

Fewer leaves

Black spots cover leaves so there is less chlorophyll available for light to be absorbed to photosynthesise and produce glucose- stunting growth

How does rose black spot spread?

Through the environment in water or by the wind

How to treat Rose black spot

Fungicides

Strip off affected leaves to prevent it spreding to other plants

What is malaria?

Protist disease spread by mosquitoes, found in hot climates

Symptoms of malaria

fever and chills

People at risk of malaria complications

Children under 5, pregnant women, elderly, people with weak immune systems

Malaria stage 1

Plasmodium parasites reproduce sexually to form sporozoites

The sporozoites travel to the mosquitoes salivary glands

When the mosquito bites another human, the sporozoites are injected into the new victim

Malaria stage 2 (liver)

Sporozoites travel to the liver

They multiply asexually inside liver cells

The liver cells burst open causing liver damage

A new parasite is released into the blood, these are called merozoites and there are many of these

merozoites infect red blood cells

Malaria stage 3

Some merozoites turn into schizonts

Schizonts burst open red blood cells causing raging fever and exhausting sweats

If the victim is bitten by a mosquito during this phase the mosquito will pick up the parasites and the whole cycle may start again

How to prevent malaria?

Insecticides and mosquito nets

Remove standing water (where they breed)

What is salmonella?

A type of bacteria that causes food poisoning

Symptoms of salmonella

Fever, stomach cramps, vomiting and diarrhoea caused by toxins

How do you get salmonella?

Eating contaminated food

Eating food that hasn't been prepared hygenically

How to prevent salmonella?

Wash hands

All UK poultry are vaccinated

What is gonorrhea?

Bacterial STD

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Symptoms of gonorrhea

Pain urinating

Yellow or green discharge from penis or vagina

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How to treat and prevent gonorrhea?

Antibiotics

Originally treated with penicillin but now new strains have become resistant

Barrier contraception

How to reduce or prevent the spread of disease

Being hygenic

Destroying vectors e.g use insecticides

isolation

vaccination- can't develop and pass on disease

1st line of defense humans

Skin is a barrier and secretes antimicrobial substances

Hair and mucus trap particles and pathogens

Stomach produces HCl

Trachea and bronchi secrete mucus to trap pathogens

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How does cillia help defend the body?

Waft mucus to the back of the throat to be swallowed

2nd line of defense

Immune system has three options:

- Phagocytosis

- Antibodies

- Antitoxins

Describe phagocytosis

Pathogens recognised as foreign via surface receptors and antigens

Phagocyte enfulfs and ingests pathogen

Phagocyte digests pathogen

pathogen can no longer do harm in the body

Describe how antibodies help protect against disease

Pathogens have unique antigens on their surfaces

When B cells come across a foreign antigen they start to produce antibodies to lock onto the pathogen so it can be found and destroyed by other WB cells

The antibodies are specific to that antigen and won't work on any others

Antibodies produced rapidly and travel all around the body

If a person is re-infected with the same pathogen B cells rapidly produce antibodies, the person is now immune

What do antitoxins do?

Counteract toxins produced by invading bacteria

What is a vaccination?

Injection of dead or inactive pathogens

These have antigens which cause the body to produce antibodies

If live pathogens of the same type appear, the B cells rapidly mass produce antibodies

immunity graph

After first infection relatively low number of antibodies are produced

After infection memory lymphocytes stay in the blood

Once re infected antibodies are rapidly produced and stay in the blood for longer than before

What is the MMR vaccine?

measles, mumps, rubella

Pros of vaccination

vaccines have helped control many infectious diseases- No more small pox and polio down by 99%

epidemics can be prevented if a large percentage of the population is vaccinated

Cons of vaccination

- vaccines don't always work- sometimes they don't give you immunity

- you can sometimes have a bad reaction to a vaccine e.g swelling, fever or seizures- although they are rare

Explain herd immunity

It occurs in a population in which a large percentage of the population is immune

People who aren't immune are less likely to catch the disease as there are fewer people likely to pass it on

What are antibiotics?

Drugs that kill or prevent the growth of bacteria without killing healthy body cells they do this by attacking the cell wall of the bacteria

Why don't antibiotics work on viruses

They don't have a cell wall

They use human cells as hosts meaning the only way to kill them would involve killing the body's cells

What do painkillers do?

They help treat and reduce symptoms and relieve pain but do not kill pathogens

Describe bacterial resistance

Bacteria mutate which can cause resistance to antibiotics

During infection, bacteria can become resistant meaning they don't get killed by antibiotics

The resistant strain survives and reproduces

The resistant strain causes serious infection

How to slow down the rate of development of resistant strains of bacteria

Doctors avoid over-perscribing antibiotics

Finish the whole course of antibiotics for the allocated time

Don't share with family

What is asprin used for and what plant is it from?

Painkiller and lowers fever

Developed from a chemical found in willow tree

What is digitalis and what plant is it from?

Used to treat heart conditions

Developed from a chemical found in foxgloves

How was penicillin discovered?

Sir Alexander Fleming noticed a dish of bacteria had mould in it and the area around the mould was free from the bacteria

He found the mould was releasing s substance that killed the bacteria (penicillin)

What do killer T cells do?

Kill bacteria causing them to self destruct

What are memory cells?

lymphocyte capable of responding to a particular antigen on its reintroduction so the immune system can take action

How are monoclonal antibodies produced?

-mouse injected with specific antigen, mouse's immune system responds and makes antibodies

- b lymphocytes taken from mouse

Lymphocytes don't divide very easily however tumour cells divide rapidly

- b lymphocytes fused with myeloma (tumour) cell to make a hybridoma

- divides quickly to produce lots of specific clones which produce monoclonal antibodies

Monoclonal antibodies collected, purified and used for a range of purposes

Give 4 uses of monoclonal antibodies

Pregnancy tests

Treat diseases

Research to find specific substances

Lateral flow tests

How can monoclonal antibodies be used to treat cancer?

Cancer cells have antigens called tumour markers

Monoclonal antibodies are made to bind to these tumour markers

Anti-cancer drugs e.g radioactive material attached to the Monoclonal antibodies

Monoclonal antibodies target the specific cells

The drug kills the cancer cells but doesn't kill normal cells near the tumour

How can monoclonal antibodies be used to find specific substances?

They can bind to hormones and other chemicals in blood

Blood samples can be tested for certain pathogens

Can locate specific molecules on a cell or in a tissue:

Antibodies bound to florescent dye

If molecules are present monoclonal antibodies attach to them and are detected using the dye

Disadvantages of monoclonal antibodies

Cause more side effects than originally expected-fever, vomiting and low blood pressure

This means they are not as widely used for treating disease

Animal cruelty as mice are injected

advantages of monoclonal antibodies

Used for a wide range of purposes

Target specific cells, not healthy human cells

What are nitrates needed for in plants?

To make proteins for growth

Lack of nitrates leads to stunted growth

What are magnesium ions needed for?

To make chlorophyll, which is needed for photosynthesis

A lack of magnesium causes chlorosis and yellow leaves

What are aphids?

Small insects that infest plants and suck sap from phloem reducing their growth rate and can kill them

Common symptoms of plant disease

Stunted growth. Spots on leaves

Patches of decay. Abnormal growth (lumps) Malformed stems or leaves. Discolouration

Give three ways to identify what disease a plant has

Look up signs in a gardening manual or website

Take infected plants to a lab where scientists can identify the pathogen

Use testing kits to identify the pathogen using monoclonal antibodies

Physical plant defences

waxy cuticle- barrier

Cellulose cell walls

layers of dead cells around stem, eg bark

plant chemical defenses

Anti bacterial chemicals

Poisons to deter herbivores

mechanical plant defenses

Thorns, hairs, spines

Leaves droop or curl when touched to knock of insects

Mimic other organisms e.g leaves that look like butterfly eggs

Some plants look like stones and pebbles

How do pain killers work?

When part of your body is injured special nerve endings send pain messages to your brain

Painkiller drugs interfere with these messages either at the site of the injury, spinal cord or the brain

Many painkillers are based off natural aspirin and opiates

What is potassium for in plants?

Healthy leaves and flowers

What are phosphates for in plants?

Healthy roots

How are monoclonal antibodies used in pregnancy tests part 1

-The section of the stick that you wee on has antibodies to a hormone produced in pregnancy and one produced in normal urine with blue beads attatched -further up the stick there are more antibodies stuck down on a strip

-The test strip immobilises the beads

How are monoclonal antibodies used in pregnancy tests part 2

-If you're pregnant:

-the hormone binds to the antibodies on the blue beads

-the urine moves up the stick, carrying the hormones and the beads

-the hormone and the beads bind to the antibodies on the strip

-the strip turns blue

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How are monoclonal antibodies used in pregnancy tests part 3

-If you're not pregnant the beads still move up the stick but only the control strip turns blue

Name three things that can be attached to monoclonal antibodies to treat cancer

radioactive substance

toxic drug

chemical which stops cells from growing and dividing

First stage of drug testing

Tested on human cells and tissues or computer models in a lab to test efficacy and toxicity

What is efficacy?

Whether the drug works and produces the effect you're looking for

What is toxicity?

measure of how harmful a substance is

second stage of drug testing

Tesing on live animals to test efficacy, toxicity and dosage

Third stage of drug testing

The drug is given to healthy volunteers to test for side effects in the body

Low dose to high dose through the trial

Tested on people suffering from the illness to find optimum dose

Peer review

What is meant by the optimum does of a drug

The dose of a drug that is the most effective and has little side effects

What is a placebo drug?

A fake version of the drug, has no effect on the body

What is the purpose of a placebo drug?

So the doctor can see the difference the drug actually makes

What is the placebo effect?

when the patient expects the treatment to work and so feels better, even though the treatment isn't doing anything

What is a blind trial?

Where patients don't know if they have the drug or the placebo

What is a double-blind trial?

A clinical trial, where neither the doctor nor patient know which drug is being tested.

What is the benefit of a double-blind trial?

So the doctors monitoring and analysing the patients aren't subconsciously influenced by their knowledge

What is peer review and why is it important?

When other scientists check that the work is valid and has been carried out rigourously. This is to prevent false claims before publication

A plant experiencing a magnesium deficiency may experience yellow leaves and stunted growth, explain

Yellow leaves due to lack of chlorophyll

less light absorbed

lower rate of photosynthesis

plant makes less glucose

plants convert less glucose into protein, growth is stunted