Bacteria, Viruses And Eukaryotes

Question 1

Why are viruses not classed as alive

Answer 1

Viruses aren’t classed as alive because they cannot reproduce independently, to do this they need a host cell.

Question 2

How big are bacteria and viruses

Answer 2

Bacteria are between 1-5um and viruses range from 1nm to 100nm.

Question 3

What are good bacteria examples

Answer 3

Good bacteria examples are
Gut bacteria (E.coli make vitamin K)
Lactobacillus (bacteria in yoghurts/cheese)

Question 4

What is the basic structure of virus

Answer 4

Basic structure of viruses is protein coat and nuclei acid on inside. Some viruses have DNA, some have RNA and contain enzymes e,g reverse transcriptase (viral protein) when they infect host cells.

Question 5

What are characteristics of viruses

Answer 5

Characteristics of viruses are
General structure (Capsid, which is a protein shell )some have envelope (stolen from host cell)
Have DNA or RNA genetic material
Linear arrangement of DNA
Not free living 
20nm average size 
No membrane bound organelles
No ribosomes

Question 6

What is capsid

Answer 6

Capsid is nucleic acid surrounded by protein shell

Question 7

Compare eukaryotic cells and viruses

Answer 7

General structure of eukaryotic cell is cell membrane and organelles whereas virus has capsid (some have envelope)
Eukaryotic cell’s have DNA, viruses have DNA or RNA
linear arrangement/chromosomes in eukaryotic cells viruses have linear arrangement NO CHROMOSOMES
Eukaryotic cells are free living, viruses aren’t
Eukaryotes larger
Eukaryotic cells have membrane bound organelles viruses don’t
Eukaryotes have ribosomes, viruses don’t

Question 8

Compare prokaryotic cells and viruses

Answer 8

Prokaryotic cells are larger than viruses
Prokaryotic cells always have DNA and some have plasmids viruses have DNA or RNA.
Prokaryotic cells have looped arrangement of DNA viruses have linear arrangement.
Prokaryotes are free living, viruses aren’t
Neither have membrane bound organelles
Ribosomes are in prokaryotic cells but not viruses

Question 9

What is lysis and what does it cause

Answer 9

Lysis is when, after reproducing in host cell, virus particles burst from cell, splitting it open.
Lysis causes cell contents being released into surrounding tissues, many enzymes and chemicals released can damage neighbouring cells. These processes cause disease symptoms produced by viral infection

Question 10

What is outer envelope of virus (only some viruses have it)

Answer 10

Outer envelope of virus is taken from host cells cell membrane, so envelope contains lipids and proteins