Topic 2C - Cells and the Immune System

Question 1

What are antigens?

Answer 1

Molecules that can generate an immune response when detected by the body.

Question 2

Where are antigens typically found?

Answer 2

Antigens are typically found on the surface of cells.

Question 3

What are foreign antigens?

Answer 3

Foreign antigens are antigens that aren’t normally found in the body.

Question 4

What are pathogens?

Answer 4

These are organisms that cause disease e.g. bacteria, viruses and fungi. All pathogens have antigens on their surface — these are identified as foreign by immune system cells, which then respond to destroy the pathogen.

Question 5

What are abnormal body cells?

Answer 5

Cancerous or pathogen-infected cells which have abnormal antigens on their surface, which trigger an immune response.

Question 6

What are toxins?

Answer 6

These are molecules that can be produced by bacteria. The immune system can respond to toxins, as well as the pathogens that release them.

Question 7

What are cells from other individuals of the same species?

Answer 7

When you receive cells from another person (e.g. an organ transplant) those cells will have some antigens different to your own. The foreign antigens trigger an immune response. This response leads to the rejection of these cells if drugs aren’t taken to suppress the recipient’s immune system.

Question 8

What are the four stages of the immune response? (4).

Answer 8

1. Phagocytosis
2. T-Cells
3. B-Cells
4. Antibody production

Question 9

What happens during phagocytosis?

Answer 9

• A phagocyte recognises the foreign antigens on a pathogen.
• The cytoplasm of the phagocyte moves around the pathogen, engulfing it.
• The pathogen is now contained in a phagocytic vacuole in the cytoplasm of the phagocyte.
• A lysosome fuses with the phagocytic vacuole. The lysozymes contained in the lysosome break down the pathogen.
• The phagocyte then presents the pathogen’s antigens — it sticks the antigens on its surface to activate other immune system cells. The phagocyte is acting as an antigen-presenting cell.

Question 10

What is a phagocyte?

Answer 10

A type of white blood cell that carry out phagocytosis.

Question 11

Where are phagocytes found in the body?

Answer 11

They are found in the blood and tissues.

Question 12

What are lysozymes?

Answer 12

Enzymes that degrade a pathogen.

Question 13

Where are lysozymes found?

Answer 13

An organelle called a lysosome.