MCB 2000 Lecture Notes - Lecture 5: Signal Transduction, Peptidoglycan, Cell Wall
23 May 2018
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Lecture 5 Notes
• Flagella and bacteria motility
o Bacteria will run and tumble away from toxic chemicals
o Chemotaxis = moving toward something desirable and away from something
undesirable
▪ Most bacteria do not go in a straight line to their desired location
• Go in a zig zag due to run and tumbling
• Bacteria cell walls
o Not all bacteria have a cell wall
o All bacterial cell walls are made of layers of peptidoglycan
▪ Peptidoglycan = NAM + NAG
▪ Peptide bridges connect the layers of peptidoglycan
▪ Gram pos bacteria have 25 layers
▪ Gram neg bacteria have 5 layers
o Gram pos bacteria have techoic acid in their cell wall
o Gram neg bacteria have an outer membrane (an extra layer)
▪ Outer membrane contains LPS (endotoxin) which is toxic to humans
▪ Outer membrane is a second layer of protection for the bacteria—makes
gram neg harder to kill than gram pos
▪ Have porins in their outer membrane
o Cell wall determines morphology (shape)
• Bacteria membrane
o Phospholipid bilayer
o Every cell must have a cell membrane
o The inside of the membrane has the hydrophobic tails and the outsides of the
membrane have the hydrophilic heads
▪ Makes the membrane selectively permeable—only certain things can get
through
▪ Drugs may need to be fat soluble to pass through the membrane
o Proteins are embedded throughout
▪ Carriers
▪ Receptors
▪ Transmembrane gates
▪ Relay information (signal transduction)
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