12 BIC - Viruses
●​ Viruses are not part of any classification system because they are not formed from
cells and are not considered living things.
●​ They do not carry out the seven life processes for themselves; instead, they take
over a host cell’s metabolic pathways to make multiple copies of themselves.
●​ Virus structure contains only
genetic material / nucleic acids
(RNA or DNA) inside a protein coat.
●​ Example of virus structure below
●​ (Note - no organelles or ribosomes)
●​ smaller than bacteria
e.g. HIV is only ~0.1 μm across
Nucleic acid
Viruses contain a core genetic material made up of either DNA or RNA. Viruses are
classified according to the type of nucleic acid they contain.
Capsid (nucleocapsid)
This is a protein coat that surrounds the core of the virus.
Envelope protein (attachment protein)
These are also referred to as attachment proteins and they stick out from the edge to let
the virus cling to a suitable host cell.
Adenosine triphosphate (ATP)
●​ ATP is the energy-carrying molecule found in all living cells and is often known as the
universal energy carrier.
●​ ATP needs to be broken down to liberate its energy. This is done by an enzyme,
ATPase.
Uses of ATP
A vast array of functions within all living organisms including: muscle contraction, active
transport, synthesis of macromolecules such as proteins, stimulates the breakdown of
substrates to make even more ATP for other uses.