Prokaryotic cells and viruses

Question 1

Plasmids

Prokaryotic cells and viruses

Answer 1

Small loops of DNA that aren’t part of main circular DNA molecule
Contain genes for things like antibiotic resistance and can be passed between prokaryotes
Not always present, some have several

Question 2

Circular DNA

Prokaryotic cells and viruses

Answer 2

No nucleus present
One long coiled-up strand and not attached to histone proteins

Question 3

Capsule

Prokaryotic cells and viruses

Answer 3

Not present in all
Made up of secreted slime
Helps to protect the bacteria from attack by cells of immune system

Question 4

Flagellum

Prokaryotic cells and viruses

Answer 4

Long hair-like structure that rotates to make prokaryotic cell move
Not present in all, some have multiple

Question 5

Binary fission

Prokaryotic cells and viruses

Answer 5

1. Circular DNA and plasmids replicate - main loop is only replicated once by plasmids can be replicated loads of times
2. Cell gets bigger and DNA loops move to opposite poles
3. Cytoplasm begins to divide and new cell walls begin to form
4. Cytoplasm divides and 2 daughter cells are produced - each daughter cell has one copy of the circular DNA but can have variable number of copies of plasmids

Question 6

Structure of viruses

Prokaryotic cells and viruses

Answer 6

Acellular - not cells
Nucleic acids surrounded by protein - they’re not even alive
Examples: HIV, influenza & rhinoviruses
No cell-surface membrane, no cytoplasm and no ribosomes
Have a protein coat called a capsid wuth attachment proteins stick out from it - let virus cling onto a suitable host cell
Viruses even smaller than bacteria

Question 7

Viral replication

Prokaryotic cells and viruses

Answer 7

Inject DNA or RNA into host cell
Hijacked cell uses its own machinery to do virus’s dirty work and replicate the viral particles
To inject their DNA or RNA, viruses have to attach to host cell surface
They use their attachment proteins to bind to complementary receptor proteins on membrane of host cell
Diff viruses have diff attachment proteins and therefore require diff receptor proteins on host cells
As result, some viruses can only infect one type of cell while others can infect lots of diff cells (influenza)