Answer

The diagram below is of the Human Immunodeficiency Virus. Some components have been labelled.

(i) ON THE DIAGRAM, identify structures A, B & C. [ 3 ]

A - Capsid / Protein coat

B - RNA / Nucleic acid

C - Enzyme / Reverse transcriptase

(ii) What is an antigen?

molecule / part of molecule / protein / glycoprotein / named molecule;

that stimulates an immune response / eq;

[ 2 ]

(iii) Suggest which labelled component of the diagram above is likely to act as an antigen. Give a reason for your answer.

glycoprotein AND

different shape to body proteins / RNA and reverse transcriptase inside virus /

phospholipids same as body's / on the surface of the virus

[ 1 ]

(iv) The cells that the virus infects are 15mm in diameter. Calculate how much larger the infected cell is than the virus. You must show your working.

187.5;; Accept 187 - 188

Allow 1 mark for HIV = 80nm;

[ 2 ]

(v) Explain why people with the Human Immunodeficiency Virus may develop AIDs.

HIV destroys, T helper / T4 cells / T lymphocytes ;

HIV replicates and increases in numbers / number of T helper cells decrease ;

immune response weakened / body can't fight disease ;

opportunistic infections / named infection(s);

body cannot destroy cancer cells / named cancer ;

AVP ; e.g. detail of action of T helper cells

[ 3 ]

[ Total: 11 ]

Log in