3.4 Prokaryotic Cells

3.4. Know the ultrastructure of prokaryotic cells, including cell wall, capsule, plasmid, flagellum, pili, ribosomes, mesosomes and circular DNA.

Ultrastructure components prokaryotic cells

• no membrane bound organelles

• 70S ribosomes

• circular DNA

• cell wall containing the glycoprotein murein

some may contain:

• plasmids (loops of DNA)

• capsules

• flagella

• pili

• cell membrane that contains folds known as mesosomes

Plasmids structure

• small loops of DNA

• not present in all prokaryotes

Plasmids function

• contain genes that can be passed between prokaryotes (e.g. genes for antibiotic resistance)

Capsule structure

• some prokaryotes are surrounded by a final outer layer known as a capsule

• not present in all prokaryotes

Capsule function

• helps protect bacteria from drying out and from attack by cells of the immune system of the host organism

Flagella structure

• long, hair-like structure that rotates

• not present in all prokaryotes

Flagella function

• enables the prokaryote to move

Pili structure

• thread like structures on the surface of some bacteria

Pili function

• enable the bacteria to attach to other cells or surfaces

Mesosomes

• infolded regions in the plasma membrane of some prokaryotic cells

Mesosomes function

• functions include: aerobic respiration, cell wall formation & DNA replication

Circular DNA structure

• genetic material of prokaryotic cells is not contained in a membrane bound nucleus

Circular DNA function

• genetic material

The area in the prokaryotic cell where the circular DNA is located is known as the…

nucleoid

Ribosomes size

• 70S (smaller than eukaryotic cells)

Ribosomes function

site of protein synthesis

Diagram of prokaryotic cells

Comparison table eukaryotes vs prokaryotes