Answers to questions on Antiviral medications

1. Although there are many different types of virus they are much smaller than bacteria. Unlike bacteria they have no nucleus or cytoplasm and are not cellular. They have a central core of DNA (or RNA) surrounded by a capsid (coat) of regularly packed protein units. Viruses cannot feed, excrete or grow. They can only reproduce inside the cells of living organisms by using material
provided by the host cell.

2. (i) Viruses multiply rapidly so by the time the disease is identified the viruses are so numerous that antiviral drugs may have little effect.

(ii) Viruses are regularly mutating so may develop ways of combating antiviral drugs.

3. They may alter the cells’ genetic material so the virus cannot use it to multiply. For example, acyclovir and ganciclovir have structures similar to deoxyguanosine so they ‘trick’ the viral enzymes into using it as a building block for the viral DNA. Other antiviral drugs may also stop the virus from multiplying by interfering with enzyme activity within the host cell. For example, both oselatamivir and zanamivir used to treat influenza, prevents the newly formed viruses from leaving the host by inhibiting the active site of an enzyme called neuraminidase which is required by the virus to stick to the host cell as it leaves.

4. A: carboxamide (amide)
B: ether (strictly it is a cyclic ether)
C. hydroxyl

5. (a) oseltamivir

(b) oseltamivir

(c) zanamivir

(d) zanamivir

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