Teddies Talks Biology - Issue 9

Ayesha Nurjahan & Emma Somers—LVI

A virus can be defined as an obligate intracellular parasite. Each virion, or viral particle, con- sists of a single nucleic acid (RNA or DNA) encoding the viral genome, surrounded by a protein coat, and is capable of replication only within the living cells of bacteria, animals or plants. Influenza The virus family Orthomyxoviridae consists of the genera Influenza virus A, B and C. Major epidemics are caused by A and B, and it is usually these two varieties that cause the flu. They have a diameter of about 100 nanometres, making them a medium sized virus.

The influenza virus is roughly spherical. It is an enveloped virus, with an outer layer that is a lipid membrane which is taken from the host cell in which the virus multiplies.

Inserted into the lipid membrane are ‘ spikes ’, which are glycoproteins, because they consist of protein linked to sugars also known as hemagglutinin (HA) and neuraminidase (NA). These are the proteins that determine the subtype of influenza virus. The HA and NA are important in the immune response against the virus: antibodies against these spikes may protect against infection. The NA protein is the target of the antiviral drugs Relenza and Tamiflu.

The Covid - 19 Virus Particle or Virion

Teddies Talks Biology I Issue 9 I June 2021

4