Unit 2 test

Question 1

Why are viruses not considered living

Answer 1

1. Not made up of cells
2. Only capable of 1 living function ie. reproduction & only with living cell
   - outside the cell, viruses are lifeless chemicals.

Question 2

list the 6 characteristics of living organisms

Answer 2

1. composed of cells
2. growth and development
3. able to reproduce
4. respond and adapt to their environment
5. obtain and use energy
6. produce wastes.

Question 3

What is capsid

Answer 3

Protein coat for protection

Question 4

What is core

Answer 4

Nucleic acid either DNA or RNA

Question 5

What are the spikes that help the virus attach to its specific host cell called

Answer 5

Receptor sites.

Question 6

What is an envelope

Answer 6

In only some viruses- surrounds the capsid and is derived from the host cell as the virus is released.

Question 7

What shapes do viruses come in and give examples

Answer 7

filaments- Ebola
spherical- HIV, COVID, Smallpox, SARS, influenza.
Geometrical-Adenovirus and Bacteriophage T4

Question 8

How are viruses classified as

Answer 8

1. the organisms they infect
   -what type of host cells and the range for ex. HIV infects WBC and the cold infects respitory cells.
2. The structure
   +size and shape of capsid
   + The nucleic acid DNA or RNA
   + If it has envelop or not.

Question 9

Why can’t viruses reproduce by themselves?

Answer 9

• Lack specific enzymes and ribosomes

- They don’t have enough energy needed to synthesise their parts.

Question 10

What happens in the attachment phase of the lytic cycle

Answer 10

• Virus attaches to host cell using its receptor sites

- injects its core (DNA) in the host cell

Question 11

What happens in the synthesis phase of the lytic cycle

Answer 11

• Viral DNA stops host protein synthesis
• Host ribosomes produce viral protein
• Viral DNA is also replicated 100’s of times using cell machinery

Question 12

What happens in the assembly phase of the lytic cycle

Answer 12

• Capsid surrounds viral DNA core

- 100’s of virus particles are put together in the cytoplasm of the host cell

Question 13

What happens in the Release phase of the lytic cycle

Answer 13

• Viruses produce enzymes to burst host cell
• 100’s of viruses are released
• These viruses infect neighbouring cells.

Question 14

What is Virulent

Answer 14

Viruses that reproduce with the lytic cycle are called virulent

Question 15

What is the special enzyme that changes RNA to DNA called

Answer 15

reverse transcriptase

Question 16

What are RNA viruses called

Answer 16

Retroviruses.

Question 17

Why are retroviruses especially lethal.

Answer 17

Because the viral DNA produced by this enzyme can splice into the host chromosome and stay dormant for months or years.

Question 18

What are 3 examples of retroviruses?

Answer 18

AIDS, Genital herpes and cold sores

Question 19

Where did viruses come from

Answer 19

Came from detached fragments of genetic material & proteins from living cells.

Question 20

Why are viral diseases difficult to

Answer 20

1. There is no drug that can kill virus in the body.
2. Some virus might be in a lysogenic cycle and be dormant like HIV
3. some viruses are oncoviruses.-cause cells to become cancerous

Question 21

What are ways to protect from getting the virus in the first place

Answer 21

Vaccines: Only true protection against viruses are vaccines.
-people are given weakend or dead version of the virus, that way your immune system builds up proper antibodies and wbc
Antiviral agents: Drugs given after infection to slow the reproduction of the virus baiscly gives your immune system a head start.

Question 22

What happens in viral vector gene therapy

Answer 22

• viral core is removed & desired human gene is added
• virus is mixed with living cells
• virus attaches to human host cell & injects the human gene.
• oncolytic virus used in targeted cancer treatment.

Question 23

Why can’t AIDS survive outside a body

Answer 23

because glycoprotein membrane around its capsid dries out

Question 24

How can AIDS spread

Answer 24

1. blood to blood
2. secretions
3. breast milk.