Topic 2C Cells and Immune System

Question 1

what are antigens

Answer 1

molecules (usually proteins) that can generate an immune response when detected by the body

Question 2

3 examples of things that can trigger immune responses

Answer 2

-pathogens
-toxins
-abnormal body cells/tumour/cancer cells

Question 3

describe the 5 stages of phagocytosis

Answer 3

• phagocyte detects foreign antigen on a pathogen

-cytoplasm of the phagocyte engulfs the pathogen

-pathogen is now contained in phagocytic vacuole called phagosome

-a lysosome (that contains lysozymes) fuses with the phagosome and breaks it down

-phagocyte then presents the pathogen’s antigens, sticking the antigens on the surface to activate T-cell response

Question 4

how do phagocytes activate T-cells

Answer 4

receptor proteins on the surface of T-cells bind to complementery antigens presented by the phagocyte

this activates the T-cells, and they stimulate response of other immune cells

Question 5

what are the 2 types of T cells

Answer 5

• T-helper cells
• Cytotoxic T cells

Question 6

describe the B-cell response once activated by T-helper cells

Answer 6

-antibody on the B-cell binds to a complementary shaped antigen

• this stimulates clonal selection and