Bacteria & Disease Pathogen – a disease causing agent Bacteria are harmful because they damage their host’s tissues by –A direct attack on the host’s tissue –By releasing poisonous toxins
Controlling Bacteria Pasteurization – heating product to a temperature that will kill most bacteria Sanitation Vaccines – a preparation of killed or weakened pathogens introduced into the body to produce immunity Antibiotics – chemical that destroys or inhibits the growth of bacteria
Viruses Virus: “poison” (Latin); infectious particles consisting of a nucleic acid in a protein coat
Viruses Viruses are not cells. They are not alive Reproduce only within a host cell. They do not have –Enzymes for metabolism –Do not have ribosomes –Do not have the equipment to make proteins
Viral structure Basic structure: –Protein coat - capsid –Nucleic acid core (RNA or DNA) –Envelope (second coat – only in enveloped viruses) envelope RNA Protein coat
Lytic Cycle Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell. The viral nucleic acid takes over protein synthesis, creating new viruses. The host cell bursts, lyses, releasing the newly formed viruses.
The Lysogenic Cycle Replication of the viral genome without destroying the host cell. Virus DNA enters host, becomes part of Hosts DNA. Host Cell copies its DNA and Virus DNA and reproduces normally but passes on Virus DNA to all its offspring. Cell with Virus DNA but not active is called a prophage. Prophage can become active and become lytic at anytime
Controlling Viruses Antibiotics don’t work against viruses –Antibiotics work by interfering with cellular processes such as protein synthesis Vaccinations –Help build up your immune system –Work well against viruses that don’t mutate