Virus Structure and Method of Invasion

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Slide 1

Virus Structure and Method of Invasion

Higher Biology

Slide 2

Introduction to viruses

Obligate parasites

Specific to type of cells they target

-poliomylelitis virus attacks nerve cells

-hepatitis virus attacks liver cells

Reproduction is their only true characteristic of being alive

Much smaller than bacteria (20-300nm)

Slide 3

Viral Structure

Not a cell!

DNA or RNA (retrovirus)

Surrounded by protective protein coat (capsid)

Genetic material carries information for multiplication

Hijacks biochemical machinery of host cell to carry these processes out

Slide 4

Bacteriophage

Slide 5

Invasion of a cell by a virus

Virus can lie dormant for many years until it comes into contact with a suitable host cell

Binds with molecules on surface of host cell

Herpes

-whole virus enters cell

Bacteriophage

-viral DNA injected via hollow tail

Slide 6

Alteration of Cell Instruction

Virus takes control of cell machinery

Depends on host for

-ATP

-supply of free nucleotides

Virus suppresses cell’s normal nucleic acid replication and protein synthesis

Manufactures many identical copies of viral nucleic acid and protein coats

Slide 7

New viral particles become assembled and become released by:

Lysis

-viral nucleic acid used to synthesise lysis enzymes

-bursting of host cell to release viral particles

OR

2. Buds contaning virus are formed

Slide 8

Slide 9

Retrovirus

Contains RNA

No DNA to transcribe into mRNA

Reverse transcriptase injected into cell by virus with RNA

-enzyme reverses normal transcription

-Produces viral DNA from RNA

-Virus uses DNA to replicate

Slide 10

Some video clips

Bacteriophage entering a cell

HIV replication