Download Virus/Bacteria Notes

Biology/O’Connor
Virus/Bacteria Notes
O’Connor
• Viruses are named after the disease
they cause or by what tissue they infect.
Polio
• Viruses are composed of nucleic acids
enclosed in a protein coat (capsid)
Smallpox
Viruses are considered to be nonliving
because:
•
•
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Don’t carry out respiration
Don’t grow
Don’t develop
Smallpox
• They do replicate… however they
require a host cell to carry out
replication.
Viral Structure:
Virus is either RNA or DNA
How does a virus infect a cell?
• Virus recognizes host cell
Attachment to a recognized cell.
• The virus and cell fit like a key and lock
Hepatitis C
• Virus enters cell by injecting nucleic
acid (RNA or DNA) into host cell.
AIDS/HIV
• Replication begins by viral nucleic acid
using the host cell’s equipment.
Ebola Virus
Two Different Cycles of viruses:
• Lytic Cycle
• Lysogenic cycle
Lytic Cycle
1.
2.
3.
4.
5.
Cell dies quickly
Attachment of virus
Nucleic Acid invades host cell
Replication
Assembly of new virus particles
Cell lyses (ruptures) and virus is
released into environment
Lytic Cycle
Lysogenic Cycle
1.
2.
3.
4.
5.
Cell does not die quickly
Attachment of virus
Nucleic Acid invades host cell
Virus becomes part of host
chromosome –(PROVIRUS)
Cell divides splitting chromosomes
and creating new cell with the virus.
Provirus leaves chromosome
cont.
6. Viral Nucleic Acid and proteins are
assembled
7. Cell lyses (ruptures) and virus is
released into environment to infect
other cells.
Lysogenic Cycle
Retroviruses:
•
RNA viruses
1. Viral RNA injected into host cell
2. Host cell’s DNA is used to make viral
DNA from viral RNA
3. Viral RNA uses reverse transcriptase
to make viral DNA
4. Viral DNA becomes a provirus
5. Keeps producing new virus without
killing cell first
• To test for a retrovirus like HIV a blood
test will be done to test for reverse
transcriptase.
Viroids
• RNA strand no protein coat
• Cause diseases in plants
Prions
• Are composed of proteins but have no
nucleic acids to carry genetic information.
• They act like viruses
• Cause diseases such as mad cow disease
& Creutzfeldt-Jakob disease.
Tobacco Mosaic Virus
• First virus to be identified
Archaebacteria & Eubacteria
* (quick review) Prokaryotes are unicellular
organisms that do not have a nucleus or
membrane-bound organelles. They are
classified as two kingdoms archaebacteria
and eubacteria.
Archaebacteria
The extremists
• live mainly in habitats where there is
usually no free oxygen available.
»Three types:
1. methane-producing archaebacteria
2. salt-loving archaebacteria
3. heat & acid loving archaebacteria
Eubacteria
• Prokayotes that live in places more
hospitable than archaebacteria inhabit and
that vary in nutritional needs.
Types:
• Heterotrophic Eubacteria live almost
everywhere.
• Photosynthetic autotrophs- make their own
energy by sunlight, so they live in places
with sunlight.
• Chemosynthetic autotrophs- make their
own energy, but do not require sun.
Bacterium
• Consists of very small cell. A bacterial cell
has all the structures necessary to carry
out its life functions.
Fighting bacteria
• Most bacteria live in hypotonic
environments, where water is always
trying to enter the cell. If you can damage
the cell wall and allow the water in it will
cause the cell to burst.
Penicillin
• Sir Alexander Flemming discovered by
mistake that penicillin would cause the cell
walls of bacteris he was growing to be
damaged.
• Damaged cell wall = burst bacteria cell
Identifying Bacteria
• Gram staining- the stain allows you to
distinguish two groups because of their
difference in the composition of bacteria
cell walls.
• Gram-stain positive turn purple
• Gram-stain negative turn pink
• Positive & negative react to different
antibiotics.
Shape also identifies bacteria
•
•
•
•
Three most common:
Spheres- called cocci
Rods- called bacilli
Spirals – called spirilla
Patterns of Growth
• Bacteria cells often grow in characteristic
patterns.
• Diplo – paired
• Staphylo – resemble grapes
• Strepto - chains
Binary Fission
• Bacteria reproduces asexually & rapidly
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•
•
•
•
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Copies chromosome
They attach
Grow larger
2 chromosomes separate, pull apart
Move to opposite ends of cell
Partition forms and you have 2 similar cells
Sexual Reproduction of Bacteria
• Conjugation- some bacteria can do this.
Transfers DNA through a bridge like
structure called a pilus.
Importance of Bacteria
• Disease causing bacteria are actually few
compared to harmless and beneficial
bacteria.
• They help fertilize fields
• Recycle nutrients on Earth
• Produce foods & medicines.
“Good” Bacteria
• Some bacteria convert N2 into ammonia by
nitrogen fixation and others that convert
the ammonia into nitrites & nitrates which
plants use.
• Swiss cheese, pickles, yogart all made by
bacteria
• Some produce antibiotics, like bacitracin
“Bad” Bacteria
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Can cause diseases like:
Strep throat
Tuberculosis
Tetanus
Lyme disease
Cavities
diptheria