viruses & bacteria chapter 19. i. viruses q: is a virus living or nonliving? viruses have: dna...
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Viruses & Bacteria
Chapter 19
I. VirusesQ: Is a virus living or nonliving?Viruses HAVE:
• DNA or RNA• Reproduce (only in living cells)
Viruses DO NOT HAVE:• Growth/development• Cells• Response to stimuli• Energy use
VIRUS = a NONLIVING particle of nucleic acid & a protein coat (capsid)
Viruses grouped based on…1) Shape
2) Having either RNA or DNA 3) The organism it infects
T4 virusRetrovirus
Chicken pox
Viral Reproduction• To reproduce, it needs a HOST CELL (a living cell) to infect.• Viruses only attach to certain cells – not all!
•Have 2 cycles: lytic & lysogenic
http://www.ptpleasantbch.k12.nj.us/bridge/genbio/microbiology.html
http://www.ptpleasantbch.k12.nj.us/bridge/genbio/microbiology.html
Which is potentially more dangerous – lytic or lysogenic viruses?
•Lysogenic viruses!
• Can spread w/o knowing it
Fighting Viral Fighting Viral InfectionsInfections
1. Vaccination • made from “dead”/weakened/altered pathogens• stimulates immune system to protect against that virus
2. Antibodies = proteins that help block/destroy pathogens
• made by white blood cells• creates memory to attack future virus exposure
HIV and HIV and AIDSAIDS
HIV = Human Immunodeficiency Virus
AIDS = Acquired Immune Deficiency Syndrome * HIV = virus that causes AIDS.
HIV & AIDS Info:• HIV is LYSOGENIC
• >42 mil. have died with HIV/AIDS
• 40,000 new infections found every year in U.S.; 50% in ages 25 or younger
• Most don’t die from AIDS – they die from another disease the immune system can’t fight off.
• HIV attacks & weakens immune system (kills helper T-cells) - unable to fight off certain infections.
Bacteria• Single-celled prokaryotes
•Living cells
•Many shapes and sizes
Structure of Bacteria1. DNA (circular, not in a nucleus)
2. Cytoplasm
4. Cell wall
3. Cell membrane
http://www.sirinet.net/~jgjohnso/typicalbacteria.html
How do bacteria reproduce?1. Binary fission –bacterium copies itself & divides into two
• asexual reproduction• makes identical bacteria
http://www.anselm.edu/homepage/jpitocch/genbio/binfission.JPG
Fighting Bacterial Fighting Bacterial InfectionsInfections
1. Antibiotics - compounds that block growth & reproduction of bacteria• If stop taking too
soon, not all bacteria get destroyed
• Antibiotic Resistance = remaining bacteria mutates & is unaffected by antibiotic2. Vaccination
3. Sterilization – using high heat to kill bacteria