1. Big Idea: Are all microbes that make us sick made of living cells?
Chapter 20- Viruses
Big Idea: Are all microbes that make us sick made of living cells?

2. 20.1 Viruses
How do viruses reproduce?
Viruses are not considered “alive”, and are made up of proteins, nucleic acids, and sometimes lipids.
Viruses can reproduce only by infecting living cells

3. Viruses vary widely in structure and size.
All viruses have surrounding coat made of protein called a capsid.
-Viruses can have a few to
hundreds of genes depending
on their complexity
Viruses attach to host and insert
their genetic material

4. Most viruses only infect a specific type of cell (plant viruses infect plant cells, animal viruses infect certain animal cells.
Bacteriophages- viruses that infect bacterial cells
Inside living cells, viruses use their genetic information to make multiple copies of themselves. Some do this immediately, while others wait.

5. Lytic infection- is when a virus enters a bacterial cell and causes it to rupture, or lyse. This releases hundreds of virus particles.
Lysogenic infection is when a host cell is not immediately taken over, but all daughter cells produced will have the virus.

7. A prophage is when a bacteriophage’s DNA becomes imbedded in the bacterial host’s DNA.
About 70% of viruses infect RNA instead of DNA. These viruses range from the common cold to HIV.
HIV is a sample of a retrovirus- and RNA virus copies RNA into DNA

8. Viruses vs. Cells Viruses Cells Need a host to survive
Do not grow/develop
Do not respond to environment
Do not obtain/use energy
DO evolve over time
Independent cell division
Grow/ develop
Obtain/use energy
Respond to environment
Change over time

9. 20.3 Diseases Caused by Bacteria and Viruses
Pathogens are disease-causing agents.
Bacteria can cause disease by destroying living cells or by releasing chemicals that upset homeostasis
Ex that damages host- tuberculosis
Ex of releasing toxins- diptheria

10. Pathogen defense Physical removal Disinfectants Food Storage
Food processing
Sterilization by heat
Washing hands and surfaces, chemical solutions to kill bacteria, low temps slow bacterial growth, boiling and frying sterilize foods, high temps cook bacteria out in meats, autoclaving

11. Antibodies block the growth and reproduction of bacteria
Vaccines are weakened or killed preparations of pathogens or inactivated toxins.
Your body has it’s own natural anti-bodies to fight off diseases and infections, but antibodies are also sold as a drug to attack bacteria.
Antibodies block the growth and reproduction of bacteria
Viruses cause disease by directly destroying living cells or by affecting cellular processes in ways that upset homeostasis
Vaccines- when injected into the body they prompt the body to produce immunity to that specific disease
Bacteria and viruses disrupts the body’s homeostasis
Viruses can attack.destroy certain cells, or can cause healthy cells to change their pattern of growth and development, which may sometimes lead to cancer

12. Virus and bacterial infection prevention= good hygiene, vaccination, limiting contact with sick individuals
Unlike bacterial infections, viruses cannot be treated with antibiotics.
Some anti-viral medications are out there and they help speed up recovery

13. Emerging diseases are diseases that appear in the population for the first time, or are old diseases that suddenly becomes harder to control
Emerging diseases are particularly threatening b/c human populations have little to no resistance to them yet.
Over time viruses mutate and evolve, which means new antibiotics and vaccines must be developed
Can become resitant to drugs/antibiotics, even multiple drugs/ antibiotics. The speed at which viruses replicate causes them to be able to evolve very quickly. This is a reason that they can sometimes be passed between species, as well as why there must be a new flu shot developed every year.

14. Prions are small protein-particles that can cause disease.
Prions can mis-fold proteins, which can damage cell function