Immunity PPQs

Question 1

Give two ways in which pathogens can cause disease. (2)

Answer 1

• releasing toxins

- directly killing the cell

Question 2

Putting bee honey on a cut kills bacteria. Honey contains a high concentration of sugar.

Use your knowledge of water potential to suggest how putting honey on a cut kills bacteria. (3)

Answer 2

• water potential in bacteria higher than in the honey
• water moves out bacteria by osmosis
• kills the cell because water is required as a metabolite (loss of water stops metabolic reactions)

Question 3

Describe how bacteria are destroyed by phagocytes. (3)

Answer 3

• phagocyte engulfs bacteria to form phagocyte
• lysosome empties contents into vacuole
• releasing lytic enzymes that hydrolyse the bacteria

Question 4

Give two structures a bacterial cell may have that a white blood cell does not have. (2)

Answer 4

• circular DNA

- cell wall

Question 5

What is an antigen? (2)

Answer 5

a foreign protein that stimulates an immune response and the production of antibodies

Question 6

What is an antibody? (2)

Answer 6

a protein specific to an antigen that is produced by B cells or secreted by plasma cells

Question 7

How do you calculate percentage change?

Answer 7

change/original x 100

Question 8

Explain the differences between the mean concentrations of antibodies in blood samples 1, 2 and 3. (4)

Answer 8

• sample 1 is before the vaccination so no antibodies released yet because the patient hasn’t encountered the virus yet
• sample 2 is the primary response where there’s been clonal expansion of B cells into plasma cells which then secrete antibodies
• sample 3 is a secondary response where the memory cells have produced the antibodies more quickly