prokaryotes

• cell surface membrane - a double layer of lipids that separates the cell's interior from its exterior environment. regulates substances entering or leaving the cell.
• cell wall - made of peptidoglycan.

  protection = the cell wall protects the cell from osmoticlysis, which can occur when the cell moves from one environment to another.

  shape = the cell wall helps maintain the cell's shape.

  dehydration = the cell wall prevents dehydration.
• ribosomes - smaller than eukaryotic ribosomes but have the same function.
• DNA - DNA is double stranded and circular in structure. found in the nucleoid, a central area of the cell that is not surrounded by a nuclear membrane.
• plasmids - small, circular DNA molecules that exist in some prokaryotic cells. small rings of double stranded extra chromosomal DNA (outside the chromosome) which can provide genetic advantages in specific environments.