VIRUSES Biology 11

A. MacAskill

WHAT IS A VIRUS? Virus is the Latin word for Poison

A Virus does not fit the six kingdom classificationThey lack the characteristics of living cells

Unlike all true organisms (even the most simple bacteria) viruses have no cellular structureNo Cell MembraneNo organelles

VIRUS CHARACTERISTICS Viruses have both non-living and

living characteristics:Non-living: Alone a virus is life-lessLiving: 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!