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?

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

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

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.

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.

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

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

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

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

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

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

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.

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