Transcript Introduction to Viruses 1


Viruses
Biology 11
McCallum
Mr.
GCO/SCO
 GCO: How are living things organized into groups for
ease of study

SCO: Describe and apply classification systems and
nomenclatures used in species (214-1)
 GCO: Introduction to the diversity present among living
things


SCO: Describe the anatomy and physiology of a
representative organism from each kingdom, including a
representative virus (316-6)
SCO: Analyze and explain the life cycle of a representative
organism from each kingdom, including a representative
virus (313-1)
Introduction
 Virus is Latin for poison
 Do not fit the 6 kingdom model
 Have both living and non-living qualities
 Unlike all true organisms (even the most simple bacteria), viruses
have no cellular structure
 No cell membrane
 No organelles (including ribosomes)
 Very small (measured in nm) relative to the size of a living cell
 Limits the amount of “information” they can carry
 5000 influenza viruses can fit on the head of a pin
Introduction (continued)
 Do not require energy – or carry out other common life processes
such as growth, respiration, and metabolism
 Cannot “survive” on their own
 Lifeless outside of cell, carrying out no functions.
 Need a living cell in order to replicate copies of itself (require host cell
machinery)
 Once within cell – replicates (using RNA/DNA information it carries).
 Highly selective and specific
 Antibiotics do not harm viruses
 Why we don’t treat the flu (Influenza virus)
 Resistance
Examples
Measles
Cold Sores
Common Cold
Influenza
Polio
The Mumps
Smallpox
What does a virus look like?
 Made up of proteins, genetic material, and sometimes lipids.
 Capsid: Protein coat (outer shell) that surrounds/encloses the
genetic material (RNA or DNA – single or double stranded).
 95% of virus make-up
 Dictates shape
 Core: Nucleic acid core under the capsid surrounding the
genetic material.
 Envelope: An additional covering on the outside of
some viruses.
 Lipid bilayer with embedded proteins
 i.e. HIV (AIDS)
Classification
 Usually classified by the type of organism they infect
a) Tobacco mosaic virus
– infects plants
b) Adenoviruses – infect
animals
c) Influenza Viruses –
infect animals
d) Bacteriophages –
infect bacteria