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Healthcare and Life Sciences

1. Viruses are not strictly considered to be living cells.
– Describe the general structure of viruses.
– Explain why viruses are not considered living cells.
(2.5 marks–LO3)
2. Label the diagram to identify the different steps of generic viral replication in the host cell.
(1.5 mark–LO3)

3. Complete the paragraph by filling in the blanks:
Human immunodeficiency virus (HIV) is especially harmful as it targets…………cells which are lymphocytes that can be differentiated by having the CD4 protein on their cell membrane. When these specific cells are activated by an antigen they release cytokines to help other …. cells, which are responsible for cellular immunity, and …. cells, which are responsible for humoral immunity, to produce immune response.
A person infected with HIV is classified as having acquired immunodeficiency syndrome (AIDS) when……………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………………………………..
(2 marks–LO1).
4. Explain in detail how the viral proteins are synthesised by the host cell, from viral DNA incorporated in the host cell genome (steps 3 & 4 in the diagram). (8 marks–LO1)
5. Antigenic variation is a challenge that faces vaccine development.
– Explain how vaccination prevents a general epidemic of a viral diseases.
– Explain the difference between antigenic drift and antigenic shift.
– Explain why it is difficult to develop vaccines for viruses that are capable of antigenic variation.
(6 marks–LO3)

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