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VIRUSES
Biology 11
A. MacAskill
WHAT
IS A VIRUS?

Virus is the Latin word for Poison

A Virus does not fit the six kingdom classification
 They lack the characteristics of living cells

Unlike all true organisms (even the most simple
bacteria) viruses have no cellular structure
 No Cell Membrane
 No organelles
VIRUS
CHARACTERISTICS
 Viruses
have both non-living and living
characteristics:
 Non-living: Alone a virus is life-less
 Living: Capable of reproduction with a
host cell
 Viruses
do not require energy – or carry out
other common life processes such as growth,
respiration and metabolism
BASIC VIRUS STRUCTURE

Very very small - measured in nanometers (nm)

Two main parts:
 Protein coat (a.k.a. capsid)
 Core (contains DNA or RNA)

Viruses can be different shapes

Virus are specific to their host
HELICAL EXAMPLE – TOBACCO MOSAIC
VIRUS
POLYHEDRAL EXAMPLE:
RHINOVIRUS( COMMON COLD)
COMPLEX EXAMPLE:
BACTERIOPHAGE
 Virus
which attacks Bacteria
VIRAL REPLICATION:
LYTIC CYCLE
LYTIC OR LYSOGENIC CYCLE
HOW CAN HUMANS AVOID VIRAL
INFECTIONS?
Vaccines: solutions that are prepared from viral
components or inactivated viruses
 An individual is injected with viral components,
their body creates anti-bodies as if the virus is real.
 These anti-bodies stay with us and as a result, a
vaccinated person is immune to that disease

UNDERSTANDING VIRUSES: VIDEO
During the video, answer the questions which were
given!