Topic 3 - Infection And Response

Question 1

What are pathogens

Answer 1

Microorganisms that enter the body and cause disease

Question 2

What type of diseases do pathogens cause?

Answer 2

Communicable (infectious/easily spread)

Question 3

What do pathogens affect

Answer 3

Both animals and plants

Question 4

What is bacteria?

Answer 4

Very small cells (1/100th of body cell) that can reproduce rapidly inside your body.
They can make you feel ill by producing toxins that damage body cells and tissues

Question 5

What is a virus?

Answer 5

They are not cells (1/100th size of bacteria).
They reproduce rapidly inside your body.
Live inside your cell and replicate using your cells machinery until the cell bursts, releasing all the new virus.
This cell damage is what makes you feel ill

Question 6

What is a protist?

Answer 6

Single-celled eukaryotes.
Some are parasites.
Parasites live ON or INSIDE other organisms and cause them damage. Often transferred by a vector.
E.g insect that carries the protist

Question 7

What is a fungi?

Answer 7

Some are single-celled, others have a body made of hyphae.
Hyphae can grow and penetrate human skin and plant surfaces, causing disease.
Hyphae can produce spores which can spread to other plants and animals.

Question 8

How are pathogens spread?

Answer 8

Water: Drinking or bathing in dirty water. E.g Cholera is a bacterial infection spread by drinking water contaminated which the diarrhoea of other sufferers.

Air: Can be breathed in. Some carried in air droplets produced when you cough or sneeze. E.g Influenza virus that causes flu is spread this way.

Direct contact: By touching contaminated surfaces, including skin. E.g Athletes foot is a fungus which makes skin itch and flake off. Most commonly spread by touching same things of an infected person eg shower floor or towel.

Question 9

What type of disease is measles? How is it spread? Effects?

Answer 9

A viral disease.
Spread by droplets from infected persons sneeze or cough.
Can develop a red skin rash and show signs of fever.
Could lead to pneumonia
You vaccinated at a young age

Question 10

What type of disease is HIV? How is it spread? Effects?

Answer 10

A viral disease.
Spread by sexual contact or sharing body fluids eg blood.
Causes flu-like symptoms for a few weeks then no symptoms for several years.
During this time HIV can be controlled with ANTIRETROVIRAL drugs to stop it replicating.
The virus attacks immune cells and when your immune system is badly damaged you have AIDS

Question 11

What type of disease is Tobacco Mosaic Virus (TMV)? Effects?

Answer 11

A viral disease.
Affects many plants.
Causes mosaic pattern on leaves of plants - parts of the leaves become discoloured.
Discolouration means the plant can’t sympathise so it stunts it’s growth.

Question 12

What type of disease is rose black spot? How is it spread? Effects?

Answer 12

A fungal disease.
Spread through water or wind
Causes purple or black spots to develop on leaves of rose plants.
Leaves can turn yellow and fall off.
Less photosynthesis can happen so doesnt grow well.
Gardeners use fungicide and strip plants of affected leaves. Leaves must be destroyed so fungus doesnt spread.

Question 13

What type of disease is malaria? How is it spread? Effects?

Answer 13

Disease caused by a protist.
Mosquitoes are vectors- they pick up malarial protist when feeding on infected animal.
Every time mosquito feeds on another animal it infects it by inserting protist.
Causes repeating episodes of fever.
Can be stopped by stopping mosquitos from breeding.
People can use insecticides and mosquito nets

Question 14

What type of disease is salmonella? Causes? Effects?

Answer 14

A bacterial disease.
Bacteria causes food poisoning.
Caused by eating food thats been contaminated with it
Causes fever, stomach cramps, vomiting and diarrhoea.
Symptoms caused by toxins bacteria produces.
In UK most poultry given a vaccination to it.

Question 15

What type of disease is Gonorrhoea? How is it spread? Effects?

Answer 15

A bacterial disease.
Spread by sexual contact.
Get pain when they urinate. Could get thick yellow/green discharge from penis or vagina.
Originally treated with antibiotic penicillin but strains of bacteria have now become resistant to it.
Treated with antibiotics and using barrier methods of contraception.

Question 16

What can we do to reduce and prevent the spread of disease?

Answer 16

Being hygienic - Washing hands before preparing food or after sneezing.
Destroying vectors - Destroying things that spread the disease. You could use insecticide or destroy their habitat.
Isolating infected person - Prevents them from passing it on
Vaccination - Means they can’t develop the infection and then pass it on

Question 17

What are body features to prevent pathogens?

Answer 17

Skin - acts as a barrier. Also produces antimicrobial substances which kill pathogens.
Hairs and mucus - In your nose. Traps particles that could contain pathogens.
Trachea and bronchi - Secrete mucus to trap pathogens. Lined with cilia ( hair-like structures which bring up mucus to back of throat where it can be swallowed)
Stomach - Produces hydrochloric acid which will kill pathogens that make it that far from the mouth.

Question 18

How does the immune system work?

Answer 18

Produces white blood cells which travel around blood and search for microbes.
1.They engulf foreign cells and digest them. PHAGOCYTOSIS.

2. Produce antibodies which lock onto invading cells so white blood cells can find and destroy them. Specific to that type of antigen(molecules on pathogen). Antibodies then produced rapidly and carried around body to find similar bacteria or viruses. If person is infected with same pathogen again, white blood cells rapidly produce antibodies to kill it. You are immune to that pathogen.
3. Produce antitoxins to counteract toxins produced by bacteria.

Question 19

How does a vaccination work?

Answer 19

Injecting small amounts of dead or inactive pathogens.
These carry antigens which cause body to produce antigens to attack.
Eg MMR Vaccine.
If live pathogens appear after that, your white cells can rapidly produce antibodies to kill off the pathogen.

Question 20

What are the PROs of a vaccination?

Answer 20

Helped control lots of communicable diseases that were once common in the UK eg smallpox.

Big outbreaks of disease (epidemics) can be prevented if large percentage of population is vaccinated. Harder for the disease to spread.

Question 21

What are the CONS of a vaccination?

Answer 21

They don’t always work. Sometimes they don’t give you immunity.

You could have a bad reaction to the vaccine.

Question 22

What are some drugs that can relieve symptoms of disease?

Answer 22

Painkillers

Antibiotics

Question 23

How do painkillers work?

Answer 23

They just relieve pain and help reduce symptoms.

They don’t actually kill any pathogens or tackle the cause of the disease.

Question 24

How do antibiotics work?

Answer 24

Kill bacteria causing the problem without kill your body cells.
Different antibiotics kill different types of bacteria.

They DONT destroy viruses because viruses reproduce using your body cells.

Question 25

What are bacteria responses to antibiotics?

Answer 25

Bacteria can mutate and sometimes cause them to become resistant to an antibiotic.

If you have an infection some bacteria might become resistant to antibiotics.

Individual resistant bacteria will reproduce. Can cause infection that can’t be treated by antibiotics.

To slow down rate of development of resistant strains doctors avoid over-prescribing antibiotics.

Question 26

Where do many drugs originally come from?

Answer 26

Chemicals produced by plants to defend themselves against pests and pathogens can be used as drugs to treat human diseases or relieve symptoms.

Eg

Aspirin - painkiller developed from chemical found in willow.
Digitalis - treat heart conditions. Developed from chemical found in foxgloves.

They can also come from microorganisms. Eg penicillin was found from mould producing it killing bacteria.

Question 27

What are the 3 main stages of drug testing/developing?

Answer 27

1)

Preclinical testing - Drugs tested on human cells and tissues in lab.

Cant use only cells and tissues if its a drug that will affect whole body systems eg testing drug for blood pressure must be used on whole animal.

2)

Test drug on live animals to test efficacy (works and produces correct effect) , toxicity and dosage.

3)

Tested on human volunteers in clinical trial.
First tested on healthy volunteers to check for harmful side effects. Very low dosage but gradually increases.
If good, tested on people suffering from illness. Find optimum dose.
Patients put in two random groups, some with placebo and some with real drug. Doctor can see actual affect.
Clinical trials often double blind so patients nor doctors know who has the drug or placebo.

Question 28

What are monoclonal antibodies? How are they made?

Answer 28

They are identical antibodies.
Produced from lots of clones of a single cell.
Fuse tumour cell and B lymphocyte to create hybridoma cell.
Hybridoma cell can be cloned to produce lots of identical cells.
These cells all produce same antibodies which can be collected.

Question 29

Explain how monoclonal antibodies are used in pregnancy tests

Answer 29

HCG hormone found in urine if pregnant

1) The part of the stick you wee on has some antibodies attached to blue beads.
2)The test strip(part that turns blue if pregnant) has more antibodies stuck onto so they cant move.
3)If pregnant the hormone binds to the antibodies on the blue beads.
Urine moves up the stick, carrying the hormone and beads.
Beads and hormone bind to antibodies on test trip.
Blue beads get stuck on the strip turning it blue
4) If not pregnant the urine moved up the stick with the blue beads but beads dont stick to test strip so it doesnt go blue.

Question 30

How are monoclonal antibodies used to treat diseases?

Answer 30

You can make monoclonal antibodies that bind to specific antigens like cancer cells.
Anti cancer drugs can be attached to these monoclonal antibodies.
Given to patient through a drip.
They only target specific cells (cancer cells) because they only bind to tumour markers (antigens on cancer cells).

Question 31

How can monoclonal antibodies be used in labs to research?

Answer 31

They can:
Bind to other hormones and chemicals in blood to measure their levels.
Test blood samples for certain pathogens.

Locate specific molecules on a cell or in a tissue.
( First theyre made to bind to specific molecule your looking for. Then antibodies are bound to fluorescent dye. If molecules are present, they will attach to them and can be detected using the dye.)

Question 32

What are some problems with monoclonal antibodies?

Answer 32

Negative side effects - fever, vomiting, low blood pressure

Question 33

What mineral ions to plants need?

Answer 33

Nitrates - needed to make proteins and therefore growth. Lack of nitrates causes stunted growth

Magnesium ions - needed for making chlorophyll, which is needed for photosynthesis. Lack of magnesium causes chlorosis and yellow leaves.

Question 34

What are common signs of plant diseases

Answer 34

Stunted growth
Spots on leaves
Patches of decay
Abnormal growths ( lumps)
Malformed stems or leaves
Discolouration

Question 35

How can you identify a plant disease?

Answer 35

Looking up signs in a gardening manual or gardening website.
Taking infected plant to laboratory where scientists can identify pathogen.
Using testing kits that identify pathogen using monoclonal antibodies.

Question 36

What are physical defences of a plant

Answer 36

Most plant leaves and stems have a waxy cuticle, which provides a barrier to stop pathogens entering.

Plant cells have a cell wall made from cellulose. These form physical barrier against pathogens that make it past waxy cuticle.

Layers of dead cells around their stems act as a barrier.

Question 37

What are chemical defences of a plant ?

Answer 37

Some can produce antibacterial chemicals which kill bacteria.

Some can produce poisons which can deter herbivores

Question 38

What are mechanical defences of a plant?

Answer 38

Some have thorns and hairs. Stop animals from touching and eating them.

Some have leaves that droop or curl when something touches them. This prevents themselves from being eating by knocking off insects and moving away from things.

Some can cleverly mimic other organisms. Eg the passion flower has bright yellow spots which look like butterfly eggs which stops butterflys laying eggs there.