Viruses

Question 1

Why are virus not considered as living

Answer 1

They always require a host cell to reproduce.

Question 2

List 5 feature of viruses?

Answer 2

• Viruses are Obligate parasites
• Cannot exist independantly from the host cell
• Not considered living
• They contain EITHER DNA or RNA, SS or DS
• They instruct the host cell to make the virus

Question 3

Compared to Bacteria and animal cells how big/small are viruses?

Answer 3

Smallest of all types of cells.

Question 4

How do viruses differ from Human cells?

Answer 4

• They have simle cellular organisation
• Cannot reproduce independantly
• Can contin either RNA or DNA

Question 5

What are the basic and then additional structures of a Virus?

Answer 5

All contain a nucleocapsid which contains DNA or RNA surrounded by a protein shell called a Capsid.

Some also have Tails or are enveloped with a membrane.

Question 6

What is the name given to the building blocks that make up the capsid?

Answer 6

Capsomers

Question 7

What is the name given to cells with envelopes and those without envelopes and give examples of each?

Answer 7

• Enveloped = Enveloped Viruses - not seen often in plants. Example - Retrovirus - HIV & Flu
• Non Enveloped = Naked Viruses - Adenovirus - Cold & Conjuctivitsis

Question 8

What are the two different shapes of Capsids?

Answer 8

Helical (rod shaped) and Icosahedral (3D triangular shape)

Question 9

What is are Bacteriophages?

Answer 9

These are viruses which attach themselves to bacteria. (The little space ship shaped viruses).

Question 10

Where does an enveloped virus get it’s envelope from?

Answer 10

When it leaves the inside of its host, it takes a little bit of the cell membrane with it.

The membrane also carries the glycoproteins, which act as recognition spikes meaning the immune system does not recognise it as a pathogen.

Question 11

How do viruses get classified?

Answer 11

1. What genetic material the contain i.e DNA or RNA
2. Their Shape
3. If they have an envelope or not
4. What organisms they attack

Question 12

What are the 5 steps to the Lytic life cycle?

Answer 12

1. Attachment
2. Entry and degeneration
3. Replication of genetic material & creation of new viruses
4. Assembly of new parts
5. Host explodes - releasing new viruses.

Question 13

What is unique about Retroviruses replication and what is the name of the unique ingredient?

Answer 13

• Enveloped ssRNA carry the enzyme REVERSE TRANSCRIPTASE, into the cell along with the RNA.
• The Enzyme then creates DNA from the virus RNA, which amalgamates with the cells DNA.

Question 14

What are the 6 steps to viral infection with a enveloped virus and what is this cycle called?

Answer 14

Lytic cycle

1. Absorption
2. Penetration - Engulfed or envelope fuses with cell membrave
3. Un-coating
4. Synthesis or Replication
5. Assembly
6. Release

Question 15

What are the stages in a Lysoentic life cycle?

Answer 15

• Attachment
• Entry (no degeneration of host DNA)
• Intergration in host DNA
• Replicate via mitosis

Question 16

Name some lytic viruses?

Answer 16

• SARS
• Cold/Flu
• Aids
• Rabies

Question 17

What is lysogenic Cycle?

Answer 17

This is when genetic material combines with the hosts genetic material and lie dormant. Allowing the cell to replicate as normal, until an environmental change occurs, activating the virus and the lytic cycle.

Question 18

Names some lysogenic viruses?

Answer 18

Herpes

HIV

Hep B

Question 19

Name 4 diseases caused by Viruses?

Answer 19

• Aids
• Flu
• Warts
• Measles

Question 20

How are non-enveloped and enveloped viruses released from the host cell?

Answer 20

Non-enveloped lyses or rupture the cell

Enveloped leaves by budding taking some of the cells membrane with them.

Question 21

How can viral disease be prevented and treated?

Answer 21

• Vaccines - contains weaked or killed virus
• Anti viral drugs

Question 22

What are the name of the recognition proteins on an enveloped virus?

Answer 22

glycoproteins