viruses
DESCRIPTION
Viruses. Characteristics of Viruses. A small, nonliving particle that invades and then reproduces inside a living cell. Nonliving because… Viruses are not cells. Do not use energy to grow or to respond to their surroundings. Cannot make food, take in food, or produce wastes. - PowerPoint PPT PresentationTRANSCRIPT
Viruses
Characteristics of Viruses A small, nonliving particle that invades and then
reproduces inside a living cell. Nonliving because…
Viruses are not cells. Do not use energy to grow or to respond to their
surroundings. Cannot make food, take in food, or produce wastes.
Act as a parasite Obtain energy from host and may cause harm to their
host.
Naming Viruses Don’t use binomial nomenclature (nonliving) Variety of names. Ex. Tobacco mosaic virus, Ebola, Epstein-Barr
Shape & Size of Viruses Viruses vary widely in
shape. Vary greatly in size.
Much smaller than bacteria.
Structure of Viruses
2 ComponentsOuter Coat
Made of proteinsProtects the virusHelps the virus attach to
the surface of the host cell
Inner Core of Genetic Material
Either DNA or RNA
How Viruses Multiply Basic Mechanism
Attachment Virus enters cell Virus’s genetic material takes over the cell’s functions Genetic material directs the cell to produce the virus’s
proteins and genetic material Proteins and genetic materials are then assembled into
new viruses KEY DIFFERENCE: Some viruses take over the
cell’s function immediately while others wait for awhile.
Lytic vs. Lysogenic Viruses Lytic “Active” Virus
Virus immediately takes over cell’s functions and new viruses are rapidly produced
Eventually the cell bursts.
Lysogenic Cycle Instead of going into
action to make more viruses, the virus’s DNA becomes part of the cell’s genetic material.
Does not affect cell’s function for awhile.
After a period of time, the cell will suddenly enter the lytic cycle.
Viral Diseases
Preventing Infectious Diseases
VaccineA substance that stimulates the body to produce
chemicals that destroy viruses or bacteria.May be made from dead or altered viruses or
bacteria.Does not cause the disease but activates the
body’s natural defenses and effectively puts the body “on alert” for possible virus or bacteria invasion.
Summary QuestionsExplain why viruses are considered
nonliving.Describe the basic structure of a virus.Describe how viruses multiply.You have a case of the flu. A friend
recommends a new treatment advertised in a magazine. The ad states that the treatment works by “deactivating the virus’s nucleus so it can’t reproduce.” Could this treatment cure you? Explain.