Viruses

Question 1

What is a virus?

Answer 1

A biological entity that has no organelles or ribosomes so needs other living cells to reproduce

Question 2

What is a vrius structure?

Answer 2

It’s a microbe with a capsid made of protein and nucleic acid

Question 3

What is the role of a capsid with a virus?

Answer 3

To protect nucleic acids and allow for recognition of host cells.

Question 4

Name 6 types of viruses?

Answer 4

Filamentous, isometric and enveloped

Bacteriophages, viroids and archeal viruses

Question 5

What are filamentous viruses?

Answer 5

Look like rods/filaments due to cylindrical protein structure around the nucleic acids

Question 6

What are Isometric viruses?

Answer 6

3D hexagons with nucleic acids in the centre

Question 7

What are enveloped viruses?

Answer 7

These are isometric viruses covered in a lipid membrane contains envelope proteins

Question 8

3 main origin theories of bacteria?

Answer 8

Regressive theory, escape theory and ancient theory

Question 9

What is the regressive virus theory?

Answer 9

Theory that viruses descended from free living organisms becoming parasitic and losing functions

Question 10

What is the virus escape theory?

Answer 10

Viruses originate from genetic material escaping from larger genomes- doesn’t explain structure

Question 11

What is the virus ancient theory?

Answer 11

Viruses have their origin in self replicating molecules in precellular world- explains difference of viruses and cellular life

Question 12

How are viruses classified?

Answer 12

Through structural traits such as capsid structure, nucleic acids and envelope structure

Question 13

What are the 7 pillars of life?

Answer 13

Organisation, metabolism, response to stimuli homeostasis, growth, reproduction and evolution.

Question 14

Viruses only have 3 pillars of life?

Answer 14

Organisation reproduction and evolution

Question 15

What are 5 stages to viral replication?

Answer 15

1) attachment
2) penetration
3) synthesis or nucleic acids and protein
4) assembly and packing
5) release/ lysis

Question 16

What is attachment of a virus?

Answer 16

The binding of a virus to receptor on the cell surface ( protein, sugars, lipids or complex)

Question 17

How does HIV attach to cells?

Answer 17

Binds a low affinity receptor and moves over cell till it binds a high affinity receptor (CD4) then it binds to co-receptor (CCR5/CXCR4) to pull virus closer then envelope fuses with the membrane.

Question 18

How do viruses penetrate cells?

Answer 18

They can move in by endocytosis if non-enveloped or by fusion if they are.
Bacteriophages use tail fibres and a needle to inject DNA into the cell

Question 19

How does a bacteriophage cause penetration?

Answer 19

Tail fibres bind then flex, tail pin then binds, tail sheath contracts and core pin is pushed through - leading to nucleic acid injection

Question 20

How does synthesis of viruses occur ?

Answer 20

Viruses use host cell to produce proteins all is regulated by virus nucleic acids

Question 21

How does synthesis occur in RNA viruses?

Answer 21

They synthesise RNA polymerase and some have RNA that can work directly as mRNA

Question 22

How does synthesis occur in ReTroviruses?

Answer 22

They contain ssRNA so need to use reverse transcriptase

Question 23

What happens at virus assembly?

Answer 23

All parts of the virus are assembled seperately and then joined

Question 24

What happens at virus release?

Answer 24

Viruses can either bud off or lyse the cell to be released budding off leads to lysis once all the membrane is used up

Question 25

What is vertical gene transfer?

Answer 25

Transfer from parents to offspring

Question 26

What is horizontal gene transfer?

Answer 26

Transfer from one lineage to another

Question 27

Examples of viruses that infect amoeba ?

Answer 27

Mimivirus, mamavirus and megavirus.

Also have Sputnik virus but must be inside of a mimi virus or mamavirus