3.2.1.2 Prokaryotic Cells + Viruses

prokaryotic cells

DNA is free in the cytoplasm and has no membrane-bound organelles, means ‘before nucleus’

DIFFERENCES with eukaryotic cells

-smaller cells

-lacks membrane-bound organelles

-smaller ribosomes (70S)

-no nucleus - instead has circular DNA that is free

-has a murein cell wall

other features of prokaryotes

-plasmids: small ring of DNA that has genes which help the survival of bacteria e.g. enzymes against antibiotics

-capsule: used as protection - sticks groups of cells together

-flagella: rotating tail propels organism

structures found in ALL bacteria not in plant cells

-circular DNA

-murein cell wall

-smaller ribosomes

viruses

-are ‘particles’ - acellular = no cell membrane, non-living = no metabolism

-need host cells to replicate

STRUCTURE of viruses

-genetic material (RNA) - can also have reverse transcriptase e.g. AIDS

-capsid: a protein coat which protects nucleic acid

-attachment proteins: allows virus to identify and attach to host cell