Prokaryotic Cells

Question 1

How big are prokaryotes?

Answer 1

0.1-10 micrometers long

They are single celled organisms

Question 2

What are the components of a prokaryotic cell?

Answer 2

Flagellum
Nucleoid (circular DNA)
Plasmid
Cell surface membrane (innermost layer)
Peptidoglycan Cell wall (middle layer)
Capsule (outermost layer)
Ribosomes (70S)

Question 3

What are the differences between eukaryotes and prokaryotes?

Answer 3

Prokaryotes
- nucleoid
- DNA isn’t associated with protein
- circular DNA
- plasmids present
- no membrane bound organelles
- 70S ribosomes
- peptidoglycan cell wall
- may have capsule

Eukaryotes
- nucleus
- DNA associated with histone proteins
- linear DNA
- no plasmids
- membrane bound organelles
- 80S ribosomes
- cellulose cell wall (or chitin in fungi)
- no capsule

Question 4

Explain the process of binary fission

Answer 4

1) circular DNA and plasmids undergo semiconservative replication. Circular is only replicated once but plasmids replicate loads of times
2) cell gets bigger and the circular DNA move to opposite ‘poles’ of the cell
3) cytoplasm begins to divide (new cell wall forms)
4) cytoplasm divides and two daughter cells are produced

Each daughter cell has one copy of circular DNA but a variable number of copies of the plasmids

Question 5

What is one way antibiotics work?

Answer 5

Prevents bacteria from making normal cell walls.

E.g. Penicillin Inhibits certain enzymes required for the synthesis and assembly of the peptide cross linkages (chemical bonds) in bacterial cell walls. This weakens the walls making them unable to withstand pressure. As water enters by osmosis the cell then bursts and the bacterium dies