Infection and response

Question 1

Measles (virus)

Answer 1

• spread through the air in droplets from an infected persons sneeze or cough
• people develop a red skin rash and show signs of a fever
• can lead to pneumonia (lung infection) or inflammation of the brain
• most people are vaccinated against it when they are young

Question 2

HIV (virus)

Answer 2

• spread by sexual contact or bodily fluids such as blood
• flu like symptoms for a few weeks then the person doesn’t experience any symptoms for several years
• the virus attacks immune cells
• if the immune system is badly damaged, it cant cope with other infections or cancers. This is the late stage of HIV or AIDS.

Question 3

Tobacco mosaic virus

Answer 3

• affects many species of plant e.g. tomatoes
• causes a mosaic pattern on the leaves of the plants and parts become discoloured
• discolouration means the plant cant carry out photosynthesis as well, so the virus affects growth.

Question 4

Rose black spot (fungal disease)

Answer 4

• causes purple or black spots on the leaves of rose plants. then turn yellow and drop off
• this means less photosynthesis so the plant cant grow well
• it spreads through the environment in water or by wind
• fungal disease can be treated with using fungicides and by stripping the plant of its affected leaves. leaves then need to be destroyed so it cant spread.

Question 5

Malaria (protist disease)

Answer 5

• caused by a protist
• the mosquitos are are vectors ( carries the protist but doesn’t get it itself)
• every time the mosquito feeds on another animal it infects it by inserting the protist into the animals bloods vessels
• malaria causes repeating episodes of fever, it can be fatal
• the spread can be reduced by stopping mosquitos from breeding
• people can be protected by mosquito nets and insecticides

Question 6

Salmonella (bacterial disease)

Answer 6

• caused by a type bacteria that causes food poisoning by producing toxins
• infected people can suffer from fever, stomach cramps, vomiting and diarrhoea
• you can get the bacterial disease by eating food that’s been contaminated with salmonella bacteria
• in the UK most poultry is given a vaccination against salmonella to control the spread of the disease

Question 7

Gonorrhoea (bacterial disease)

Answer 7

• bacterial disease
• sexually transmitted disease (STD) passed on by sexual contact e.g. unprotected sex
• symptoms are pain when urinating; thick yellow/green discharge from the vagina/penis
• originally treated with the antibiotic penicillin - now some strains have become resistant to it
• treatment with antibiotics and using barrier methods of contraception (e.g. condoms) help prevent the spread of it

Question 8

How can the spread of disease be reduced/prevented?

Answer 8

• being hygienic e.g. washing hands
• vaccination - means people cant develop the disease and pass it on
• isolating infected individuals - prevents from passing it on to others
• destroying vectors - using insecticides or destroying habitats

Question 9

What are examples of defence in the human body?

Answer 9

• skin, it acts as a barrier to pathogens and also produces antimicrobial substances which kill pathogens
• hairs and mucus in your nose trap particles that could contain pathogens
• stomach produces hydrochloric acid which kills pathogens
• trachea and bronchi are lined with cilia - hair like structures which push mucus up to the back of the throat where it can be swallowed

Question 10

What are the three ways your immune system attacks pathogens?

Answer 10

• Consuming, white blood cells engulf pathogens and digest them. this is called phagocytosis
• Producing antibodies, when white blood cells come across a foreign antigen they will start to produce proteins called antibodies to lock onto invading cells so they can be destroyed. The antibodies produced are specific to that type of antigen. The antibodies are then rapidly produced and carried around the body to find all similar pathogens. If the same person is infected again with the same pathogen the white blood cells will produce the same antibodies to kill it so they are naturally immune.
• Producing antitoxins, counteract toxins produced by invading bacteria

Question 11

What is a vaccination?

Answer 11

• injecting small amounts of dead or inactive pathogens.
• these carry antigens that cause your body to produce antibodies to attack them
• but if pathogens of the same type appear after that, the white blood cells can rapidly mass-produce antibodies to kill of the pathogen so you don’t get ill.

Question 12

What are the pros of vaccination?

Answer 12

• They have helped control lots of communicable diseases that were once common in the UK (smallpox no longer occurs at all)
• Epidemics ( big outbreaks of disease) have been prevented if a large percentage of the population is vaccinated

Question 13

Cons of vaccination?

Answer 13

• Don’t always work
• Can sometimes have a bad reaction to vaccine e.g swelling but this is very rare

Question 14

What are painkillers?

Answer 14

A drug e.g aspirin for relieving pain. They don’t kill pathogens only reduce the symptoms.

Question 15

What are antibiotics?

Answer 15

• antibiotics e.g. penicillin kill or prevent the growth of bacteria without killing your own body cells
• different antibiotics kill different types of bacteria so its important to be treated with the right one
• they don’t kill viruses
• the use of antibiotics has reduced the number of deaths from communicable diseases caused by bacteria

Question 16

How can bacteria become resistant?

Answer 16

• They can mutate which can cause them to become resistant to an antibiotic
• if you have an infection some bacteria might be resistant to the antibiotics so only the non- resistant strains will be killed
• the resistant bacteria will survive and reproduce so the population of the resistant bacteria will increase (natural selection)
• this can cause serious infection that can’t be treated with antibiotics

To slow down the rate of development of resistant strains, its important for doctors to avoid over prescribing antibiotics.

Question 17

What drugs were discovered by studying plants used in traditional cures?

Answer 17

• Aspirin is used as a painkiller to lower fever, it was developed from a chemical in willow
• Digitalis is used to treat heart conditions, it was developed from a chemical in foxgloves

Question 18

What drugs were extracted from microorganisms?

Answer 18

• This is extracted from microorganisms
• Alexander Fleming was clearing out some petri dishes containing bacteria. He noticed one of the petri dishes also had mould on it and the area around the mould was free of bacteria
• He found the mould was producing a substance that killed bacteria ( the substance was penicillin)

Question 19

What are the three stages of developing drugs?

Answer 19

1. Preclinical testing - drugs are tested on human cells and tissues in the lab
2. Testing on live animals - this is to test efficiency, to find out about its toxicity and to find the best dosage

3.
- Testing on human volunteers in a clinical trial - first the drug is tested on healthy volunteers to make sure it doesn’t have any harmful side effects.
- At the start of the trial a very low dose of the drug is given and this is gradually increased.
- If the results on the healthy volunteers are good the drugs can be tested on people suffering from the illness. The optimum dose is found.
- To test how well the drug works, patients are randomly put into two groups. One group is given the new drug the other is given a placebo ( a substance like the drug being tested but doesn’t do anything) so the doctor can see the actual difference the drug makes
- Clinical trials are blind, often double blind for the patient and the doctor so the doctors monitoring the patients and analysing the results aren’t subconsciously influenced by their knowledge.
- The results of the drug trail aren’t published until they are peer reviewed, to prevent false claims

Question 20

How do you get monoclonal antibodies?

Answer 20

• Inject a mouse with the chosen antigen, the mouses immune system response occurs and antibodies are created
• B-lymphocytes ( type of white blood cell) are taken from the mouse
• Tumour cells from the lab divide lots so they fuse with a mouse B-lymphocyte to create a cell called a Hybridoma
• Hybridoma cells are then cloned to get lots of identical cells that all produce the same antibodies. The antibodies can then be collected and purified

Question 21

How are monoclonal antibodies used in pregnancy tests?

Answer 21

• A bit of the stick you wee on has some antibodies to the hormone with blue beads attached
• The test strip also has some antibodies to the hormone stuck onto it
• If you are pregnant the hormone binds to the antibodies on the blue beads and the urine moves up the stick carrying the hormone and blue beads
• The beads and hormone bind to the antibodies on the test strip, turning it blue

Question 22

how can monoclonal antibodies be used to treat diseases?

Answer 22

• cancer cells have antigens on their cell membrane that aren’t found on normal body cells which are called tumour markers
• in the lab you can make monoclonal antibodies that will bind to these tumour markers
• an anti cancer drug can be attached to these monoclonal antibodies, this might be a radioactive substance, a toxic drug or a chemical that stops cancer cells from growing and dividing
• the antibodies are given to the patient through a drip
• the antibodies target the specific cancer cells because they only bind to the tumour markers
• the drug kills the cancer cells but doesn’t kill normal body cells

Question 23

what can monoclonal antibodies be used for?

Answer 23

• bind to hormones and other chemicals in blood to measure their levels
• test blood samples for certain pathogens
• locate specific molecules on a cell or in a tissue

Question 24

how can monoclonal antibodies be used to find specific substances?

Answer 24

• monoclonal antibodies are made that will bind to these specific molecules you’re looking for
• the antibodies are the bound to a fluorescent dye
• if the molecules are present, the monoclonal antibodies will attach to them, and they can be detected using the dye

Question 25

what are the advantages of monoclonal antibodies?

Answer 25

- cancer treatment, the side effects of an antibody based drug are lower than for standard chemotherapy or radiotherapy (because other cancer treatments can affect normal body cells)

Question 26

what are the disadvantages for monoclonal antibodies?

Answer 26

- they cause more side effects than were originally expected e.g. fever, vomiting and low blood pressure - this means they are not as widely used

Question 27

what mineral ions do plants need?

Answer 27

- nitrates are needed to make proteins and therefore growth. a lack of them causes stunted growth - magnesium ions are needed to make chlorophyll which is needed for photosynthesis. plants with a lack of them suffer from chlorosis and have yellow leaves if plants don’t get these they suffer deficiency symptoms

Question 28

what are the common signs when plants have diseases?

Answer 28

- stunted growth - spots on leaves - patches of decay - abnormal growths e.g. lumps - malformed stems or leaves - discolouration

Question 29

what’s an example of a insect that can infest and damage a plant?

Answer 29

aphids

Question 30

how can plant diseases be identified?

Answer 30

- looking up the signs in a gardening manual or a gardening website - taking the infected plant to a laboratory where scientists can identify the pathogen - using testing kits that identify the pathogen using monoclonal antibodies

Question 31

what are physical defences of plants?

Answer 31

- waxy cuticle provides a barrier to stop pathogens entering - plant cells are surrounded by cell walls made from cellulose, these form a physical barrier against pathogens - layers of dead cells around their stems to act as a barrier to stop pathogens entering e.g. bark in trees

Question 32

what are chemical defences of plants?

Answer 32

- some can produce antibacterial chemicals which kill bacteria e.g. mint plant - others produce poisons which can deter herbivores e.g. tobacco plants, foxgloves

Question 33

what are mechanical defences of plants?

Answer 33

- thorns and hairs to stop animals from touching and eating them - leaves that droop or curl when something touches them meaning they can prevent themselves from being eaten by knocking insects off themselves and moving away from things - mimic other organisms e.g. the passion flower has bright yellow spots on its leaves that look like butterfly eggs ,this stops other butterflies laying their eggs there