Microbiology Flashcards
Draw and label the structure of a prokaryotic cell
Flagellum Pilus Circular DNA Plasma Membrane 70s Ribosome Peptidoglycan Cell Wall Slime Capsule Plasmid
What is the function of the plasma membrane in a prokaryote?
- barrier between the environment and the cytoplasm
- controls entry and exit of substances into and out of the cell
What is the function of the peptidoglycan cell wall in a prokaryote?
- prevents osmotic lysis
- rigidity and cell structure
What is the function of the slime capsule in a prokaryote?
- protect against other cell attack
- prevents cell drying out
What is the function of pili in a prokaryote?
Transferring plasmids (genetic information) by conjugation
What is the function of the flagellum in a prokaryote?
For mobility
What is the function of the plasmid in a prokaryote?
- contains extra bacterial genes, e.g. bacterial resistance
- can be exchanged between bacteria during conjugation allowing spread of resistance
What are the 3 bacterial shapes?
- Bacillus (Rod)
- Coccus (sphere)
- Spirillum (Spiral)
What are prokaryotes?
- no membrane bound nucleus
- no membrane bound organelles
- small ribosomes (70s)
- cell wall made up of peptidoglycan
- small cells, 0.5-5um
- reproduce by binary fission
What is the structure of gram positive bacteria?
- cell wall has a thick layer of peptidoglycan and a plasma membrane
What happens to gram positive bacterium in the Gram stain?
- peptidoglycan holds onto crystal violet dye
- dye is not washed out by ethanol and therefore appears purple in the Gram stain
What is the structure of Gram negative bacterium?
- thick outer layer of lipopolysaccharides with a thin layer of peptidoglycan
- plasma membrane beneath
What happens to Gram negative bacterium in the Gram stain?
- crystal violet dye is removed when rinsed with ethanol (dissolves the stained lipopolysaccharide layer)
- peptidoglycan is stained with the counter-stain and therefore appears pink in the gram stain test
What antibiotics interfere with Gram positive bacterium?
- Penicillin
- prevents bonds interlinking peptidoglycan forming
- when the bacteria divide, the cell walls are weak and collapse
- water uptake by osmosis bursts the cell
What antibiotics interfere with Gram negative bacterium?
- Require antibiotics that interfere with the cell’s metabolism/protein synthesis
- e.g. vancomycin
- penicillin is not effective as the outer layer protects the peptidoglycan