Topic 3 - Infection and response - Fighting Disease

Question 1

What defences does the body have to stop pathogens ENTERING the body?

Answer 1

1. The skin acts as a natural barrier to pathogens. It also secretes antimicrobial substances which kill pathogens.
2. Hairs and mucus in your nose trap particles that could contain pathogens.
3. The trachea and bronchi secrete mucus to trap pathogens.
4. The trachea and bronchi are lined with cillia that waft mucus up to the back of the throat where it can be swallowed.
5. The stomach produced HCL. This kills pathogens that make it that far from the mouth.

Question 2

What happens when pathogens make it into the body?

Answer 2

1. Your immune system activates.
2. The most important part of the immune system are white blood cells. They are constantly patrolling for microbes.

Question 3

How do white blood cells defend against pathogens?

Answer 3

1. White blood cells can engulf foreign cells and digest them. This is called phagocytosis.
2. They produce antibodies. When B-lymphocytes come across a foreign antigen they will start to produce proteins called antibodies to lock onto the invading cells so that they can be found and destroyed by other white blood cells. These antibodies are specific to that type of antigen - they wont lock on to any others.
3. Antibodies are then rapidly produced and carried around the body to find all similar pathogens.
4. If the person is infected with the same pathogen again, the white blood cells will rapidly produce the antibodies to kill it - the person is naturally immune to that pathogen.
5. They produce antitoxins

Question 4

What is a vaccination?

Answer 4

1. Vaccinations involve injecting dead or inactive pathogens into the body.
2. These carry antigens which cause your body to produce antibodies to attack them even though the pathogen is harmless.
3. This means that if pathogens of the same type occure after that, the white blood cells can rapidly mass-produce antibodies to kill off the pathogen.

Question 5

Pros of vaccinations?

Answer 5

1. They have helped to control lots of communicable diseases that were once common in the UK.
2. Epidemics can be prevented if a large percentage of the population has been vaccinated.

Question 6

Cons of vaccinations?

Answer 6

1. Vaccines don’t always work - sometimes they dont give you immunity.
2. You can sometimes have a bad reaction to a vaccine.

Question 7

What do painkillers do?

Answer 7

They help to reduce the symptoms

Question 8

How can you kill bacteria outside the body?

Answer 8

Antisteptics and disinfectants

Question 9

What do antibiotics do?

Answer 9

1. They kill or provent the growth of the bacteria causing the disease.
2. Different antibiotics kill different types of bacteria.

Question 10

Do antibiotics destroy viruses?

Answer 10

1. No.
2. Viruses reproduce using your body cells, so it is very difficult to develop drugs that kill the virus without killing the body’s cells.

Question 11

How can bacteria become resistant to antibiotics?

Answer 11

1. Bacteria can mutate - sometimes the mutations cause them to be resistant to an antibiotic.
2. If you have an infection, some of the bacteria might be resistant to antibiotics.
3. This means when you treat the infection, only the non-resistant strains of bacteria are killed.
4. The resistant bacteria will survive and reproduce, and the population of the resistant strain will increase.
5. This means that the antibiotics can’t cure the disease
6. This is an emergency - if scientists can’t develop new antibiotics soon, we may no longer be able to cure bacterial diseases.

Question 12

How to slow down the rate development of resistant strains?

Answer 12

1. You have to avoid over-prescribing antibiotics.
2. You have to finish the whole course of antibiotics.

Question 13

What plant does aspirin come from?

Answer 13

1. Aspirin is a painkiller used to lower fever.
2. It was developed from a chemical found in willow.

Question 14

What plant does digitalis come from?

Answer 14

1. Digitalis is used to treat heart conditions.
2. It was developed from a chemical found in foxgloves.

Question 15

How was penicillin discovered?

Answer 15

1. Alexander fleming was clearing out petri dishes containing bacteria. He noticed that one of the dishes of bacteria also had mould on it and the areas of mold was free of bacteria.
2. He found that the mould (Penicillium Notatum) on the petri dish was producing a substance that killed the bacteria - this substance was penicillin.

Question 16

Developing drugs 8 marker?

Answer 16

1. In preclinical testing, drugs are tested on human cells and tissues in the lab.
2. The next step in preclinical testing is to test the drug on live animals. This is to test for efficacy, to find out its toxicity and to find the best dosage.
3. If the drug passes the tests on animals then it is tested on healthy human volunters in a clinical trial. This is to make sure the drug doesn’t have any harmful side effects when the body is working normally.
4. If the results are good, the drugs are tested on people suffering from the illness, and the optimum dose is found.
5. To test how well the drug works, patients are randomly put into two groups. One is given the new drug, the other is given a placebo. This allows for the placebo effect.
6. Clinical trials are often double blind - neither the patient or doctor knows which is the drug and which is the placebo until the results have been gathered. This is to prevent bias.
7. The results are then peer reviewed to prevent false claims.

Question 17

Physical plant defences?

Answer 17

1. Most plant leaves and stems have a waxy cuticle, which provides a barrier to stop pathogens entering
2. Cell walls made from cellulose provide a physical barrier against pathogens that make it past the waxy cuticle
3. Plants have layers of dead cells around their stems e.g. bark that act as a barrier to stop pathogens entering

Question 18

Chemical plant defences?

Answer 18

1. Some can produce antibacterial chemicals which kill bacteria e.g. the witch hazel and mint plant
2. Other plants produce poisons which can deter herbivores

Question 19

Mechanical plant defences?

Answer 19

1. Some plants have thorns and hairs that stop animals from touching and eating them
2. Other plants have leaves that droop or curl when something touches them so they can prevent themselves from being eaten by insects by knocking them off
3. Some plants mimic other organisms e.g. the passion flower has bright yellow spots on its leaves, butterfly egg