 Maintain homeostasis  Reproduction  Cellular organization  Metabolism (use energy)  Contain genetic information

Viruses are particles of nucleic acid, protein, and in some cases, lipids. Differ widely on shape and size. Viruses are not considered to be living because……… Use the machinery of other cells to produce more viruses.

 A typical virus is composed of a core of DNA or RNA surrounded by a protein coat.  Remind me of the Hershey-Chase experiment….

 A viruses protein coat is called its capsid. › Proteins on the capsid bind to receptors on the surface of a cell; most viruses are highly specific.  Plant virus infect plant cells.  Animal viruses infect only certain related species.  Bacterial viruses only infect certain types of bacteria.

 What is it? › A virus that infects bacteria.

 Lytic Infection- a virus enters a cell, makes copies of itself, and causes the cell to burst.

 Lysogenic infection- virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell’s DNA. › The viral DNA that’s embedded in the host’s DNA is called a prophage.  Does not lyse the cell right away; remains inactive for a period of time.  Eventually the prophage will remove itself from the host cell DNA and will begin synthesizing new virus particles.

 Some viruses contain RNA-> these are known as retroviruses. › When they infect a cell they produce a DNA copy of their RNA.  Why are they called retroviruses?  HIV is an example of a retrovirus.

 The best way to protect against most viral diseases lies in prevention, often by the use of vaccines. › Regarding vaccines…….

 What is a prokaryote? › Single-celled organisms that lack a nucleus.  Bacteria have been divided into two groups, what are they? › Eubacteria and archaebacteria.  Which is larger?  Eubacteria

 Live almost everywhere, including the human intestines. › Escherichia coli (E. coli)  The cell walls of eubacteria contain this: › Peptidoglycan, a carbohydrate.

 Archaebacteria lack the peptidoglycan of eubacteria, and live in extreme environments. › Hot springs › Utah’s Great Salt Lake › Includes methanogens  Where are some methanogens found? What do they produce?

 Shape: › Bacilli, cocci, and spirilla.  Cell Walls: › Gram +/Gram – › Stains the peptidoglycan in the cell walls.  Movement: › Flagella, glide, some are stationary. Proteus vulgaris