Day 8) Viruses & Bacteria - Life Science 11 - Joanna Peng

Parasites

Parasites live in or on other living organisms, causing them harm.

All viruses are parasites; all viruses require a host; all parasites are organisms. Viruses are not affected by any known antibiotic. Antibiotic kill bacteria.

Host

The living organism the parasites live on.

Viruses

Tiny non-living particles that invade and then replicate inside a host cell. Viruses are not affected by any known antibiotic. Antibiotics kill bacteria; however, viruses are not bacteria.

Envelope virus

Virus is spherical, surrounded by a membrane envelope. Virus is somewhat regular in shape.

Helical virus

Virus is a hollow tube filled with amino acids. Virus is somewhat regular in shape.

Icosahedral virus

Virus is made of triangles fused together in a sphere. Virus is geometric in shape.

Bacteriophage

Virus is icosahedral with a tail, infects bacteria. Virus is geometric in shape.

What are the main structures of a virus?

• Protein coat: protects the virus

• Capsid: contains the genetic material

• Surface proteins act like keys that fit specific receptors (locks) on host cells. If the key fits the lock, the virus can attach to and infect that cell.

• Some virus may also have an outer membrane called an envelope.

• The virus cannot infect every cell in your body because not every cell has the correct receptor.

How do viruses get energy?

From the host cell.

How do viruses reproduce? Active

Virus attaches to the cell. The viral genetic material takes over and begins to replicate immediately.

How do viruses reproduce? Hidden.

The virus’s genetic material joins/combines or remains inside the host cell’s genetic material and stays inactive/dormant until something causes it to become active and reproduce.

What characteristic do viruses share with living things?

1) They can reproduce but only inside a living cell

2) They can mutate or change

3) They have DNA or RNA

Why are viruses considered non-living/which characteristics of living things do viruses not have)?

1) Not made of cells

2) No metabolism/don’t need food or energy

3) Can be crystallized, dehydrated, and stored indefinitely. They can come to “life” (are active) only when injected inside a living cell.