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Published byJean Caldwell Modified over 7 years ago
Viruses & Bacteria Chapter 19
I. Viruses Q: 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 virus Retrovirus
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
Which is potentially more dangerous – lytic or lysogenic viruses? Lysogenic viruses! Can spread w/o knowing it
Fighting Viral Infections 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 AIDS 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 Bacteria 1. DNA (circular, not in a nucleus) 2. Cytoplasm 4. Cell wall 3. Cell membrane
How do bacteria reproduce? 1. Binary fission –bacterium copies itself & divides into two asexual reproduction makes identical bacteria
Fighting Bacterial Infections 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 antibiotic 2. Vaccination 3. Sterilization – using high heat to kill bacteria
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