2.2.1 - Prokaryotic cells Flashcards
List some structures of a prokaryotic cell.
Cell membrane
Plasmids
70S ribosomes
Slime capsule
Nucleoid (circular strand of DNA)
Differences between prokaryotic cells and eukaryotic cells?
No membrane bound organelles
DNA found in cytoplasm
70S ribosomes - not 80S
Have plasmids
What part of a bacterial cell allow it to attach to surfaces?
Pili
What is the function of lipid droplets and glycogen granules?
Act as nutrient stores
What is the name given to the infoldings of the cell membrane in a bacterial cell?
Mesosome
What is peptidoglycan made from?
Polysaccharide chains
Feature of a bacterial cell wall?
Hypertonic meaning water can move in by osmosis.
What is significant about a gram positive bacteria cell wall?
Thick peptidoglycan layer
What is significant about a gram negative bacteria cell wall?
Thin peptidoglycan layer
What is the method of testing between gran positive and gram negative bacterial cell walls?
Stain with crystal violet/iodine
Wash with alcohol
Add red safranin stain
What are the colours of gram positive and gram negative bacteria after being tested with stains?
Gram positive = purple/blue
Gram negative = Red
Why does gram positive bacteria turn purple/blue when tested with stains?
Crystal violet/iodine gets stuck in peptidoglycan layer.
Resists being decolourised with alcohol.
So don’t pick up red safranin stain.
Why does gram negative bacteria turn red when tested with stains?
Crystal violet/ iodine doesn’t get stuck in peptidoglycan layer when washed with alcohol.
So turns red when stained with red safranin stain.
What part of bacterial cells do antibiotics target?
Cell walls and ribosomes.
What do beta lactam antibiotics do?
Inhibit formation of peptidoglycan cell wall.
What do glycopeptide antibiotics do?
Polar molecules which work against gram positive as they can’t penetrate cell wall.
What do polypeptide antibiotics do?
Work against gram negative bacteria as they interact with phospholipids.
How can antibiotic treatment identify type of bacterium?
If antibiotics work, the bacteria is gram positive.
Gram positive have a thick peptidoglycan layer in cell wall.
Therefore larger target site for antibodies.
What are obligate anaerobes?
Bacteria that are destroyed by normal oxygen concentrations.
What are obligate aerobes?
Bacteria that require oxygen to survive.
What are facultative anaerobes?
Bacteria that can live in the presence of oxygen but don’t need it.
Some antibiotics affect the enzymes involved in the growth of bacteria.
(i) Explain why Gram positive bacteria and Gram negative bacteria react differently to some antibiotics.
Gram positive bacteria have a thick layer of peptidoglycan in their cell wall.
Some antibiotics inhibit the enzymes involved in the formation of peptidoglycan so are effective against gram positive bacteria.
Some antibiotics are not able to cross the peptidoglycan layer so they are only effective against gram negative bacteria.
