Unit 1: “Get a Life” Chapters 7 and 19 Bacteria and Viruses Unit 1: “Get a Life” Chapters 7 and 19

Bacteria

Prokaryote Characteristics Prokaryotes can be identified by the following characteristics: No nucleus or organelles Cell shape Way they move Way they obtain energy

Bacteria Unicellular prokaryotes (no nucleus) Found everywhere Use just about anything for energy. Move using whip-like structures called flagella or oozing a slime layer.

Bacterium with Flagella

Bacteria Bacteria also come in different shapes Rod-shaped are called bacilli Round are called cocci Spiral

E. coli Bacterium

Role of Bacteria in the Environment There are many helpful bacteria, such as the bacteria found in your intestines. Some Bacteria: Carry out photosynthesis Recycle Nutrients Carry out nitrogen fixation (for plants)

Bacteria Reproduce by fission. (They split in two.) Bacterial infections can be treated medically using antibiotics, which will target the living prokaryotic cells. The growth rate of most bacteria will be slowed at low temperatures. Most bacteria die at high temperatures (above 100oF).

Viruses A virus is NOT a “true” cell. It is not considered living. Viruses exist for one purpose: to reproduce! They cannot reproduce on their own. Viruses MUST have a host cell copy their DNA for them.

Viruses All viruses are made of proteins and nucleic acids. Viruses have two parts: Protein coat = capsid DNA or RNA that contains the instructions for replication

Viral Reproduction A virus will attach itself to a host cell. It then injects its DNA into the cell. The cell copies the DNA, which makes more of the virus.

Viral Reproduction Eventually, the cell will burst releasing all the new viruses. Viruses cause infections by entering body cells and replicating.

Viral Infections Antibiotics are an ineffective treatment. Viruses can be prevented using a vaccine. A vaccine contains an inactive or weak version of the virus. It exposes your immune system to the virus so that the body can build up defenses.

Bacteria vs. Viruses Prokaryote Not living 1000x smaller than eukaryotes Reproduces by fission Treated using antibiotics Not living Much smaller than a bacterium Must have a host copy its DNA Vaccines used for prevention