BIOL 2004 Lecture Notes - Lecture 1: Electric Motor, Multiprotein Complex, Electrochemical Gradient
3 May 2018
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Department
Course
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Prokaryote Cell Organisation
March 1, 2016
- Basic structure of prokaryotes
- Cell membrane
External Projections
- Usually made from protein – must be secreted to form extracellular structure
- Usually anchored to cell membrane or outer membrane (or both)
- Motor proteins are attached to cell membrane in gram-negative
- Examples
o Bacterial flagella
▪ Consists on thin, flexible helical filaments (5-20 um long; ~15 nm thick
*thinner than a single microtubule in eukaryotes)
▪ Present in many bacterial groups – often only expressed under certain
conditions
▪ Function: swimming locomotion
▪ Monotrichous = cell with one flagellum
• Still use run and tumble behaviour for chemotaxis *turns flagella
on/off
▪ Peritrichous = many flagella *more common
o Ex. Escherichia coli
▪ *see function and structure below
o Fimbriae and pili
▪ Many different kinds *look like small hairs
▪ Thin rods/ tubes of Protein
▪ 3-6 nm thick ; ~1 um long
▪ Typical roles:
• Adhesion (e.g. genetic exchange/ pathogenesis)
• Locomotion (on surfaces) *gliding movement
▪ Sex pili = bring cells undergoing genetic exchange together
Flagellum Structure:
- Multiprotein complex
- Basal body = ring like structure of motor proteins in cell membrane surrounding rotor
- A series of intrinsic proteins surround basal body
- Filament – of flagellin protein
- A rotary motor is powered by a proton motive force (PMF) *through the membrane down
the proton gradient
Flagellum Function:
- Can rotate clockwise or counter-clockwise *different motility effects
- In some peritrichous cells:
o If all are counter-clockwise – flagellar bundle forms; straight-line “run”
o If 1+ are clockwise – no bundle; random “tumble”; cell will spin in place
- Swimming
o Alternating runs and random tumbles random walk through space
find more resources at oneclass.com
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Document Summary
Usually made from protein must be secreted to form extracellular structure. Usually anchored to cell membrane or outer membrane (or both) Motor proteins are attached to cell membrane in gram-negative. Examples: bacterial flagella, consists on thin, flexible helical filaments (5-20 um long; ~15 nm thick. Basal body = ring like structure of motor proteins in cell membrane surrounding rotor. A series of intrinsic proteins surround basal body. A rotary motor is powered by a proton motive force (pmf) *through the membrane down the proton gradient. Can rotate clockwise or counter-clockwise *different motility effects. In some peritrichous cells: if all are counter-clockwise flagellar bundle forms; straight-line run , if 1+ are clockwise no bundle; random tumble ; cell will spin in place. Swimming: alternating runs and random tumbles random walk through space, random walk can be biased by altering the frequency of random tumbles in response to a cue, e. g.
