Exam-style Questions: Immunity

1. a) Explain what is meant by the 'first line of defence'.

b) (i) What are antigens?

(ii) How are antigens used in the first line of defence?

(Marks available: 3)

Answer

Answer outline and marking scheme for question: 1

Give yourself marks for mentioning any of the points below:

a) Physical and chemical barriers to disease. They are non-specific.

(1 mark)

b) (i) Chemical markers on each cell

(ii) Your body recognises the antigens on your cells as your own anything with different antigens to you stimulates an immune response.

(2 marks)

(Marks available: 3)

2.
a) Describe the five stages of phagocytosis of a bacterium by a neutrophil?

b) Explain one weakness of the second line of defence.

(Marks available: 6)

Answer

Answer outline and marking scheme for question: 2

Give yourself marks for mentioning any of the points below:

a) (i) The bacteria is attracted to the membrane of the neutrophil.

(ii) Phagocytosis, the bacteria is engulfed.

(iii) Once in the neutrophil, lysosomes (vesicles containing digestive enzymes) will form and make their way towards the phagosome containing the bacteria.

(iv) The lysosomes fuse with the phagosome

(v) The bacteria is killed and digested by the enzymes.

(5 marks)

b) It can't deal completely with any one particular micro-organism (some pathogens will nearly always survive this attack)

It can not remember past infections

(1 mark)

(Marks available: 6)

3.
a) Describe briefly what a vaccine is made up of.

b) State two measures used to create safe vaccines.

(Marks available: 3)

Answer

Answer outline and marking scheme for question: 3

Give yourself marks for mentioning any of the points below:

a) Small quantities of the antigen attached to the disease causing organism.

(1 mark)

b) The disease cell may be altered, killed or use altered toxins.

(2 marks)

(Marks available: 3)