VirusesFor EOC Review

IV. Preventing Bacterial Disease

1. Vaccine- A preparation of a weakened or killed pathogen, such as a bacterium or virus. Body produces antibodies.

2. Antibiotics- compounds that block the growth and reproduction of bacteria.

1. A substance, such as penicillin, that is capable of destroying or weakening certain microorganisms, especially bacteria or fungi, that cause infections or infectious diseases. Antibiotics are usually produced by or synthesized from other microorganisms, such as molds.

V. Viruses

1. Structurea) Composed of Nucleic Acids

DNA or RNA– not bothb) Surrounded by a capsid (protein coat)c) Fibers/ Proteins for attachment to host celld) Can be seen with electron microscope only

V. Virusesd) Varies greatly in size & can only be seen with electron microscope

V. Viruses2. Reproduction- Must infect a host in order to

reproducea) Attach to host cellb) Insert DNA or RNAc) Use machinery and resources of host cell to

produce more virus copiesd) Highly specific

Virus types only can infect certain hosts Ex: bacteriophage only can

infect bacteria

VI. Types of Virus Replication1. Lytic Cycle

a) Infection/ attachment• Injects DNA or RNA into host

b) Growth• Virus DNA shuts down normal cell activities

to make copies of itselfc) Replication

• Uses resources of host to make copiesd) Cell lysis

• Infected host cell bursts and releases new virus copies to that will infect other cells

What is happening in each step?

VI. Types of Virus Replication

2. Lysogenic Cyclea) Virus integrates DNA into host

• Virus remains inactive• Does not lyse host cell immediately

b) Prophage- viral DNA embedded into host DNAc) When conditions change virus can switch to lytic

infection

Are viruses alive??