Viruses and Bacteria

Viruses

• A tiny, non-living particle that enters and then reproduces inside a living cell

• Needs a host, which provides a source of energy

• Parasite– Lives on or in a host and can cause

harm

Shapes

• Round, rod-shaped, bricks, threads, bullets, robot-like shapes

Sizes

• Smaller than cells

• Cannot be seen with school microscopes

• Measured in nanometers– 1 billionth of a meter

Structure

• Two basic parts– Protein coat which protects itself– Inner core

• Genetic material

Surface Proteins

• Can attach to host cells

• Lock and key

• Specific

Multiply

• Inside host cell– Virus’s genetic material takes over many

cell functions– Instructs cell to produce the virus proteins

and genetic material– Make new virus’s

Bacteria

• Anton van Leeuwenhoek (late 1600s)– Scrapings from teeth– Could only see shapes, but not the parts

inside the cells

Bacteria

• Prokaryotes– Genetic material is not contained in a

nucleus (have no nucleus)– Lack some other structures as well

Shapes and Sizes

• Spherical, rodlike, spiral

• Vary in size, average is about 0.5-1 micrometer– 1 millionth of a meter