3.2.1.2 Structure of prokaryotic cells and of viruses

Question 1

What is binary fission in bacteria?

Answer 1

1. Circular chromosomes and plasmids replicate - 2 chromosomes present
2. Each chromosome move to opposite side of the cell and attaches to the cell membrane
   Cell grows and elongates
3. Membrane starts to pinch in from the top and bottom towards the middle
4. When cytoplasm and cell membrane is divided into two, cell wall starts growing into the gap
5. Two new daughter cells are formed

Question 2

What organelles are present in prokaryotic cells, but not eukaryotic cells?

Answer 2

Plamids
Capsule (slime layer)
Flagella

Question 3

How do the same organelle differ between prokaryotic and eukaryotic cells

Answer 3

No membrane-bound organelles in the cytoplasm
70S ribosomes instead of 80S
No nucleus, instead have circular DNA
Cell wall made of murien (glycoprotein)

Question 4

What is the structure of virus?

Answer 4

Nucleic acids (core of genetic material - DNA/RNA) surrounded by a protein coat - capsid with attachment proteins sticking out from it

Attachment proteins let virus cling into a suitable host cell

Have no cell-surface membrane, cytoplasm or ribosomes

Question 5

How do virus replicate?

Answer 5

1. Virus attaches to host cell receptor proteins (complementary to proteins on its membrane)
2. Genetic material is released into host cell (RNA and Reverse Transcriptase)
3. Viral RNA is turned back into DNA using RT

4.Genetic material and proteins are replicated by host cell’s machinery (enzymes / ribosomes), with addition of viral DNA

5. Viral components assemble
6. Replicated viruses released from host cell