Viruses: Dead or Alive?

Viral Structure Viruses are not cells Basic Structure: Protein Coat surrounding a Nucleic Acid Core (either DNA or RNA)

Virus Size Very, very small About 100 times smaller than a bacteria About inches long Most can only be seen with electron microscopes

Virus Categories DNA viruses Stable, do not mutate rapidly Single-stranded or double- stranded Smallpox, Hepatitis B

RNA viruses Mutate rapidly, unstable Single-stranded or double- stranded HIV, Rhinovirus

Are Viruses Alive? Only 1 characteristic of life: reproduction Can only reproduce inside a host cell No growth, no metabolism, no homeostasis.

Discovery of Viruses 1935-Wendell Stanley discovered that a chemical was poisoning tobacco plants. The chemical was made of RNA and a protein—the first discovered virus. Virus = Poison in Latin

Viral Reproduction Two Processes Lytic Cycle 1. Lytic Cycle-active cycle, causing disease Viruses in the Lytic Cycle are called pathogens Lysogenic Cycle 2. Lysogenic Cycle-inactive cycle, no disease symptoms Viruses in the Lysogenic Cycle are called proviruses.

Lytic Cycle 1.Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell. 2.The viral nucleic acid takes over protein synthesis, creating new viruses. 3.The host cell bursts (lyses), releasing the newly formed viruses.

Lysogenic Cycle (pt 1) 1.Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell. 2.The cell will continue to reproduce as normal, replicating the virus’s genetic material along with its own. There is no damage to the cell yet.

Lysogenic Cycle (pt 2) 3.A change in the cell’s environment can cause the virus to activate. 4.Once activated, the virus enters the Lytic Cycle.

In humans, all viruses stay in nerve cells during the lysogenic cycle. We all have about: 10 trillion cells 100 trillion bacterial cells 1000 trillion viruses

Prions and Viroids Prions -- protein particles that cause problems with a cell’s natural protein formation. Cell can’t work right without the right proteins. Viroid – single strands of RNA that can affect plants

Viral Diseases Common cold, the flu, rubella, mumps and measles, smallpox, hepatitis, polio, AIDS, some cancers and rabies Treatments: Best: Immunizations and vaccinations Next Best: Avoidance Anti-virals for some diseases Can treat symptoms for some

Bacteria: Classification and Structure

Bacteria are Prokaryotes Pro – before Karyon – nucleus The simplest forms of life Earth’s first cells were prokaryotes

Earth’s most abundant life forms They can survive in many environments They can get energy from many different sources

Two Kingdoms of Bacteria ArchaebacteriaEubacteria

Archaebacteria Live in extreme locations: Oxygen-free environments Concentrated salt-water Hot, acidic water

Differences between two kingdoms 1.Different structure of cell wall and cell membrane Archaebacteria is more closely related to eukaryotes than to eubacteria! 2.Archaebacteria can only live in extreme environments—extinct everywhere else 3.Archaebacteria evolved first— oldest organisms on the Earth

Common things between kingdoms 1.Unicellular 2.Prokaryotic 3.Asexual Reproduction 4.Heterotrophic or Autotrophic 5.Motile or Sessile

Pili—used to attach bacteria to other cells

Structure of Bacteria Two parts to Bacteria Structure: Arrangement Shape

Arrangement Paired: diplo Grape-like clusters: staphylo Chains: strepto

Shape Rod: bacillus Spheres: coccus Spirals: spirillum

Examples Streptococcus: chains of spheres Staphylospirillum: clusters of spirals Diplobacillus: Pairs of rods

Getting Energy 1.Photosynthetic—get energy from Sun 2.Chemosynthetic—get energy from chemicals in the environment 3.Heterotrophic—get energy from other things; mainly decomposers

Bacterial Diseases Bubonic plague, cholera, cavities, dysentary, lyme disease, typhoid fever, MRSA, acne Treatment: Best: Avoidance Next Best: Antiboitics-kill bacteria, but not viruses. Some bacteria have developed immunity

Gram-staining Depending on the type of proteins in the bacteria’s cell membrane, they can either be stained by a dye or not. Since the proteins control what goes in and out of the bacteria, that tells us what antibiotics to use.

Positive! Negative!

Good Bacteria Escherichia coli — helps digest our food Fermentation – allows us to make pickles, cheese, vinegar and beer Industrial uses – acetone and butane; sulfur-processing, cleaning up oil spills