The Immune System And Its Defenses

Question 1

What is a pathogen?

Answer 1

A pathogen is a living microorganism or virus that causes disease.

Question 2

What types of pathogens are there?

Answer 2

Bacteria - Bacteria are one called organisms without a nucleus. Although most bacteria are harmless, some cause diseases.

Fungi - a simple eukaryotic organism that contains one or more cells

Protozoa- one called organisms with a nucleus, making them eukaryotic organisms

Virus- viruses are non - living collections of protein and DNA that must reproduce inside of living cells.

Question 3

What are the 5 ways that pathogens spread?

Answer 3

Food
Water
Sexual contact
Sneezing and coughing
Touching dirty surfaces

Question 4

What are the names of the two types of white blood cells?

Answer 4

Phagocytes

Lymphocytes

Question 5

How does phagocytosis destroy pathogens?

Answer 5

1. The phagocytes’ membrane surrounds the pathogen and the enzymes found inside the cell
2. Then they break down the pathogen in order to kill it.

Question 6

How do lymphocytes help destroy pathogens?

Answer 6

They recognise proteins on the surface of pathogens called antigens

1. A) Lymphocytes detect that both the proteins and pathogens are foreign as they are not naturally occurring within your body, and they produce antibodies. This can take a few days, during which time you may feel ill.

B) the antibodies created by the lymphocytes causes pathogens to stick together, and make it easier for phagocytes to engulf

2. A) some pathogens produce toxins which make you feel ill. Lymphocytes can also produce antitoxins to neutralise these toxins

Question 7

What are physical barriers against infection and how do they work?

Answer 7

Skin- if it is cut or grazed it immediately begins to heal itself often forming a scab which prevents infection as the skin acts as a physical barrier.

Nose- cells in the nose produce mucus that trap pathogens before they can enter the lungs. When the nose is blown, mucus is removed and any pathogens trapped in it.

Question 8

What are chemical barriers and how do they work?

Answer 8

Stomach acid- there is hydrochloride acid in the stomach that is strong enough to destroy any pathogens that have been caught in mucus in the airways or consumed in food and water.

Tears- tears contain enzymes

Question 9

Why do vaccines have dead or altered pathogens?

Answer 9

As antigens are injected in the body, the immune system can safely learn to recognise them as harmful pathogens, produce antibodies and remember them for the future in case they arrive again