B3.1. Communicable disease

Question 1

Name four ways in which diseases caused by pathogens can be spread.

Answer 1

Through air, through water, direct contact (e.g. STDs), vectors.

Question 2

Name four ways in which the spread of diseases can be reduced or prevented.

Answer 2

Hand-washing, safer sex practices, vaccination, eradication of vectors.

Question 3

What is a pathogen?

Answer 3

A microorganism that causes infectious disease.

Question 4

Name the four classes of pathogens.

Answer 4

Viruses, bacteria, protists, fungi.

Question 5

Why does is there a short delay between infection by a pathogen and feeling ill from the infection?

Answer 5

Bacteria and viruses may reproduce rapidly inside the body.

Question 6

Why might viruses cause more damage than bacteria?

Answer 6

Viruses live and reproduce inside cells, causing cell damage.

Question 7

In what way might bacteria cause damage to cells and tissues?

Answer 7

Bacteria may produce poisons (toxins) that damage tissues and make us feel ill.

Question 8

What are the symptoms of the measles virus?

Answer 8

Fever and a red skin rash.

Question 9

How is the measles virus spread?

Answer 9

Inhalation of droplets from sneezes and coughs.

Question 10

Why are children vaccinated against the measles virus?

Answer 10

Measles is a serious illness that can be fatal if complications arise.

Question 11

What are the initial symptoms of HIV infection?

Answer 11

HIV initially causes a flu-like illness.

Question 12

What is the aim of antiretroviral drugs?

Answer 12

To stop the virus from replicating.

Question 13

How does HIV lead to AIDS?

Answer 13

When the body’s immune system becomes so badly damaged it can no longer deal with other infections or cancers.

Question 14

How is HIV spread?

Answer 14

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

Question 15

What is TMV and what type of organism does it affect?

Answer 15

A widespread plant pathogen affecting many species of plants including tomatoes.

Question 16

What are the symptoms of TMV?

Answer 16

A distinctive ‘mosaic’ pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis.

Question 17

How does Salmonella cause disease and what are the symptoms?

Answer 17

Spread by the bacteria being ingested in food, or on food prepared in unhygienic conditions. Fever, abdominal cramps, vomiting and diarrhoea are caused by the bacteria and the toxins they secrete.

Question 18

How is the spread of Salmonella controlled in the UK?

Answer 18

In the UK, poultry are vaccinated against Salmonella to control the spread.

Question 19

How is the bacterial disease Gonorrhoea spread?

Answer 19

Gonorrhoea is spread by sexual contact.

Question 20

How can the spread of the bacterial disease Gonorrhoea be controlled?

Answer 20

Treatment with antibiotics or use of a barrier method of contraception e.g. condoms.

Question 21

What are the symptoms of Gonorrhoea?

Answer 21

Thick yellow or green discharge from the vagina or penis and pain on urination.

Question 22

What issues are there with the treatment for Gonorrhoea?

Answer 22

Was easily treated with the antibiotic penicillin until many resistant strains appeared.

Question 23

What is rose black spot disease?

Answer 23

A fungal disease where purple or black spots develop on leaves, which often turn yellow and drop early.

Question 24

How is rose black spot spread?

Answer 24

It is spread in the environment by water or wind.

Question 25

How does rose black spot affect a plant?

Answer 25

It affects the growth of the plant as photosynthesis is affected due to discolouration & destruction of the leaves.

Question 26

How can rose black spot be treated?

Answer 26

Using fungicides and/or removing and destroying the affected leaves.

Question 27

What causes malaria?

Answer 27

A protist.

Question 28

How is malaria spread?

Answer 28

Spread via mosquito.

Question 29

How is malaria treated?

Answer 29

Anti-malarial drugs.

Question 30

How is the spread of malaria controlled?

Answer 30

Eradication of vectors such as mosquitos and/or use of mosquito nets at night to avoid being bitten.

Question 31

What are the four first line non-specific defense systems of the human body against pathogens?

Answer 31

Skin, nose, trachea and bronchi, stomach.

Question 32

What is the role of the immune system?

Answer 32

If a pathogen enters the body the immune system tries to destroy the pathogen.

Question 33

Name three ways in which white blood cells help to defend against pathogens.

Answer 33

Phagocytosis, antibody production, antitoxin production. (Make sure you know how each of these work)

Question 34

What is the purpose of vaccination programmes?

Answer 34

Can prevent illness in an individual and reduces spread of the pathogen in a population.

Question 35

What does a vaccination contain?

Answer 35

A small quantity of dead or inactive forms of a pathogen.

Question 36

How does the contents of a vaccine prevent future infection?

Answer 36

It stimulates the white blood cells to produce antibodies. If the same pathogen re-enters the body the white blood cells respond quickly to produce more of the correct antibodies quickly, preventing infection.

Question 37

How do antibiotics work?

Answer 37

Killing infective bacteria inside the body through many different ways e.g. preventing the cell wall from forming or preventing DNA from being replicated.

Question 38

What are the current concerns around antibiotic treatment?

Answer 38

The emergence of bacterial strains resistant to antibiotics means many antibiotics no longer work effectively.

Question 39

What are painkillers used for?

Answer 39

Painkillers and other medicines are used to treat the symptoms of disease but do not kill pathogens.

Question 40

What are the issues with treating viral diseases?

Answer 40

Antibiotics cannot kill viral pathogens. It is difficult to develop drugs that kill viruses without also damaging the body’s tissues.

Question 41

Name three examples of drugs extracted from plants and microorganisms and state what they are used for.

Answer 41

“1. The heart drug digitalis originates from foxglove plants

2. The painkiller aspirin originates from willow trees
3. Penicillin was discovered by Alexander Fleming from the Penicillium mould”

Question 42

How are most drugs manufactured now?

Answer 42

Synthesised by chemists in the pharmaceutical industry. (However, the starting point may still be a chemical extracted from a plant or microorganism.)

Question 43

Why do new drugs need to be tested and trialled?

Answer 43

New drugs are extensively tested for toxicity, efficacy and dose to check that they are safe and effective.

Question 44

What is preclinical testing?

Answer 44

Preclinical testing is done in a laboratory using cells, tissues and live animals.

Question 45

What is involved in the first stage of a clinical trial?

Answer 45

Clinical trials use small numbers of healthy volunteers and patients. Very low doses of the drug are given at the start of the clinical trial.

Question 46

If a drug is found to be safe in the first stage of testing, what happens next?

Answer 46

If the drug is found to be safe, further clinical trials on larger groups of healthy volunteers and patients are carried out to find the optimum dose for the drug.

Question 47

What is a double blind trial?

Answer 47

In double blind trials, some patients are given a placebo. Neither the doctor nor patient know whether they have been given a placebo in order to reduce potential bias.