Pathogens

Question 1

What are pathogens?

Answer 1

Pathogens are micro-organisms that cause disease.

Question 2

Some examples of pathogens.

Answer 2

They include micro-organisms such as bacteria, viruses, fungi and protozoa.

Question 3

What diseases do pathogens cause?

Answer 3

Pathogen	Disease
Bacteria	        Cholera
Viruses	        Influenza (flu)
Fungi	        Athlete’s foot
Protozoa	        Malaria

Question 4

What are parasites?

Answer 4

Parasites are organisms that live on or in a host organism.

Question 5

How do parasites benefit from living on/in a host?

Answer 5

The parasite benefits from this arrangement, but the host suffers as a result. For example, tapeworms are parasites.

Question 6

How do parasites live on/in a host?

Answer 6

They live inside another animal, attaching themselves to the host’s gut and absorbing its food. The host loses nutrition, and may develop weight loss, diarrhoea and vomiting.

Question 7

Do parasites kill their hosts?

Answer 7

Parasites do not usually kill the host, as this would cut off their food supply.

Question 8

What is malaria and how is it caused?

Answer 8

Malaria is a disease caused by a protozoan, a type of single-celled organism.

Question 9

How is malaria passed?

Answer 9

The malaria parasite is spread from person to person by mosquitoes.

Question 10

How do mosquitoes feed?

Answer 10

These insects feed on blood and the malaria parasite is passed on when the mosquito takes a meal.

Question 11

What are organisms that spread disease called?

Answer 11

Organisms that spread disease, rather than causing it themselves, are called vectors. The mosquito is the vector for malaria.

Question 12

How can you prevent yourself from getting malaria?

Answer 12

The spread of malaria can be controlled by avoiding contact with the vector. One way to do this is to avoid being bitten by mosquitoes, for example using mosquito netting at windows, doors and around beds.

Question 13

How can mosquitoes be killed?

Answer 13

The mosquitoes may be killed using insecticides. The parasite itself can be killed by giving infected people drugs such as Lariam.

Question 14

Give three examples of diseases that are not caused by pathogens and so are not infectious.

Answer 14

• Scurvy is caused by vitamin C deficiency
• Anaemia is caused by iron deficiency
• Diabetes and cancer are disorders of the body.

Question 15

How is cancer formed?

Answer 15

A cancer happens when cells begin to divide out of control. They form tumours that can sometimes be felt as an unusual lump in the body.

Question 16

Give some examples of a diet and lifestyle that can increase the risk of developing certain cancers.

Answer 16

• Smoking increases the risk of lung cancer
• Using sunscreen reduces the risk of skin cancer
• Eating more fruit and vegetables reduces the risk of bowel cancer.

Question 17

What two types of tumours are there, how does it form and how can you recognise them?

Answer 17

• Benign tumours grow slowly and are usually harmless – warts are benign tumours
• Malignant tumours often grow more quickly and may spread throughout the body.

Question 18

How does the skin help to protect the human body and stop pathogens getting in?

Answer 18

The skin covers the whole body. It protects the body from physical damage, microbe infection and dehydration. Its dry, dead outer cells are difficult for microbes to penetrate, and the sebaceous glands produce oils that help kill microbes.

Question 19

How does stomach acid help to prevent pathogens from getting into the body?

Answer 19

Hydrochloric acid in the stomach kills harmful micro-organisms that might be in the food or drink that we swallow.

Question 20

What do pathogens do once inside the body?

Answer 20

They reproduce.

Question 21

What do viruses do once inside the body?

Answer 21

Viruses reproduce inside cells and damage them, while escaping to infect more cells.

Question 22

What does bacteria do once inside the body?

Answer 22

Bacteria produce toxins - poisons. Cell damage and toxins cause the symptoms of infectious diseases.

Question 23

What helps fight off pathogens and other viruses?

Answer 23

Once pathogens enter the body, the immune system destroys them. White blood cells are important components of the immune system.

Question 24

What do one blood cells do to help kill pathogens?

Answer 24

• Engulf pathogens and destroy them
• Produce antibodies to destroy pathogens
• Produce antitoxins that neutralise the toxins released by pathogens.

Question 25

What foreign chemical do pathogens carry?

Answer 25

Antigens. These are foreign to the body.

Question 26

What are anti-bodies?

Answer 26

These are proteins that have a chemical ‘fit’ to a certain antigen.

Question 27

What happens once you have been infected with a particular pathogen? Why is this? What is this called?

Answer 27

Once you have been infected with a particular pathogen and produced antibodies against it, some of the white blood cells remain.
If you become infected again with the same pathogen, these white blood cells reproduce very rapidly and the pathogen is destroyed.
This is active immunity because you make your own antibodies.

Question 28

What is passive immunity?

Answer 28

Sometimes you may be treated for infection by an injection of certain antibodies from someone else. This is passive immunity because you receive antibodies, rather than make them yourself.