Viruses

Question 1

Why aren’t viruses classified as living organisms?

Answer 1

Because they lack a metabolism of their own

Question 2

What does a virus’s replication depend on?

Answer 2

The metabolism of the cells they infect

Question 3

What are three things all viruses have?

Answer 3

Nucleic acid core
Capsid protein coat
Some may have external envelope of membranes made of lipids and proteins

Question 4

In what ways can viral infections be treated?

Answer 4

Using antivirals to inhibit replication

Question 5

How are viruses classified?

Answer 5

How they replicate their nucleic core, nature of their capsid, shape and the organisms they infect

Question 6

What host does lamda bacteriophage have?

Answer 6

Bacteria

Question 7

What is the nature of the nucleic acid core of bacteriophages?

Answer 7

Double stranded DNA

Question 8

What does the lambda bacteriophage look like?

Answer 8

Like a spider?? Has a head and tail tube then tail fibres

Question 9

How is the nucleic core copied in lambda bacteriophage?

Answer 9

DNA transcribed to mRNA

Question 10

What host does the tobacco mosaic virus have?

Answer 10

Plants

Question 11

What does the tobacco mosaic virus look like?

Answer 11

Canal containing RNA surrounded by capsid of polypeptide building blocks (like a car wash)

Question 12

What is the nature of the nucleic acid core of tobacco mosaic virus?

Answer 12

Single stranded RNA

Question 13

How is the nucleic acid core copied in tobacco mosaic viruses?

Answer 13

RNA copied directly to mRNA

Question 14

What is the host of the ebola virus?

Answer 14

Humans

Question 15

What does the ebola virus look like?

Answer 15

Kinda like a worm - RNA strand inside surrounded by protein coat

Question 16

What is the nucleic acid in ebola?

Answer 16

Single stranded RNA

Question 17

How is nucleic acid copied in ebola?

Answer 17

RNA directly copied to form mRNA

Question 18

What is the host of HIV?

Answer 18

T-cells

Question 19

What does the HIV virus look like?

Answer 19

Circular with glycoproteins on the capsule and enzymes inside

Question 20

What nucleic acid is in HIV?

Answer 20

RNA

Question 21

(briefly) How is nucleic acid copied in HIV?

Answer 21

RNA reverse transcribed into DNA and then incorporated into the host DNA then transcribed into mRNA

Question 22

What is latency?

Answer 22

When a pathogenic virus remains dormant. The virus/its nucleic acid are in the cell but they aren’t controlling its activities

Question 23

What is episomal latency?

Answer 23

When the viral nucleic acid remains inactive but free in the cytoplasm or nucleus of the infected cell

Question 24

What is proviral latency?

Answer 24

When the viral nucleic acid becomes incorporated into the DNA of the infected host cell

Question 25

If a virus can't be treated with antivirals, what should be done?

Answer 25

Focus on prevention of spread

Question 26

How can you prevent the spread of a virus?

Answer 26

``` Put patients in quarantine Isolate affected areas Promote good hand-washing Use antibacterials Wear protective equipment Dispose of waste carefully ```

Question 27

How does the drug trial process differ in emergencies?

Answer 27

Drugs can be fast-tracked Rather than going through pre-clinical, phase I, II, III then review, the drugs going into circulation after phase I if found to be safe

Question 28

What are the ethics of using untested drugs?

Answer 28

May have unknown side effects

Question 29

Give an example of an incident where emergency drugs were needed

Answer 29

Ebola outbreak in 2014

Question 30

Name the stages of the lytic cycle

Answer 30

``` Attachment Penetration Synthesis Assembly Lysis ```

Question 31

Explain the lytic cycle

Answer 31

Virus cell attaches to the cell surface receptors of the host cell Injects its RNA/DNA Interrupts host cell replication and its own proteins are synthesised using host cell enzymes and nucleotides Proteins are assembled Repeats until lysis occurs and cell dies

Question 32

What does virulent mean?

Answer 32

Disease causing

Question 33

Which cycle causes virulent viruses?

Answer 33

Lytic cycle

Question 34

What is the difference between the lytic cycle and lysogenic cycle?

Answer 34

Lytic - viral DNA replicates independently of the host DNA. Leads to the death of the cell by lysis Lysogenic - Viral DNA incorporated into cell DNA and replicates as the cell replicates

Question 35

Explain the retrovirus cycle

Answer 35

Glycoproteins on the surface of HIV attach to CD4 receptors on T-cell Viral capsid fuses with the T-cell membrane and injects its RNA RNA --> DNA using reverse transcriptage DNA incorporated into host DNA with integrase DNA is then latent Read by host cell ribosomes and HIV proteins made using host cell nucleotides and enzymes Proteases cut it up and combine with RNA to make viruses Leaves cell by exocytosis New cells infect other T-cells.

Question 36

How can HIV cause death?

Answer 36

Causes either the lysis of T-cells or causes them to be killed by T-killer cells Immune system weakened B cells can't be activated Opportunistic diseases enter and cause death e.g. TB

Question 37

What's the difference between the genetic info in viruses and bacteria?

Answer 37

In viruses it can be RNA or DNA, in bacteria it's always DNA DNA is circular in bacterium, RNA is linear in viruses Plasmids in bacteria, no plasmids in viruses

Question 38

Why is unbroken skin a good barrier to HIV?

Answer 38

Keratin in skin surface | Forms impermeable barrier