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MMG Transport and Motility


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What are 4 concentration dependent transport mechanisms?
1) Osmosis
2) Simple diffusion
3) Facilitated diffusion
4) Active transport
What is simple diffusion?
-molecule moves from high concentration to low concentration
-no energy required
-concetration reaches equilibrium
What is facilitated diffusion?
-channel protein (permease) binds to molecule causing a conformational change
-no energy required
-concentration reaches equilibrium
What is active transport?
-molecule moves against the conc gradient (for more in cell usually)
-energy required
-NO equilibrium
What are three types of active transport mechanisms?
-simple transport
-group translocation
-ABC transport
What is simple transport (not diffusion)?
-molecule is not altered
-energy required in form of protonmotive force
What is group translocation?
-molecule is chemically altered during transport
-ATP required when a phosphate froup is added
What is ABC transport?
-ATP-binding cassette is located in the periplasm of Gram- bacteria
-requires binding protein and energy ATP
How many alpha helices do transmembrane proteins contain?
What are three types of simple transporters (the actual proteins)
How does a Uniporter transport molecules?
-one molecule in one direction
-co-transports two molecules in opposite directions at same time
-co-transports two molecules in same direction at same time
Where did transporters evolve from? What evidence is there of this?
-all evolved from one possible common transporter
-they all show similar similarities in structure even though there are hundreds of them!
What happens during group translocation?
-molecule is chemically altered during transport
*The transported molecule is altered during the process, so the cell in not fighting a conc gradient!
Give a common example of group translocation.
-phosphotransferase system: transports some sugars (glucose, mannose, fructose). Requires ATP as source of added phosphate group
What is ABC transport stand for?
How does it get its energy?
ATP-Binding Cassette Transport
-Coupled to ATP hydrolysis as energy source
In Gram- bacteria, where are transporting proteins located?
How about Gram+?
-in periplasmic space
-anchored to cytoplasmic membrane
What happens during ABC transport?
-transported molecule binds to a transporting protein
-this interacts with a membrane-spanning protein
How do prokaryotes move?
How about microbial eukaryotes?
-pseudopod, cilia, flagella
What is flagellum?
-a long filamentous structure attached to the cytoplasmic membrane
Where are flagella located on the bacterium?
What is each type known as?
1) monotrichous (polar): at one end of cell
2) amphitrichous: both ends of cell
3) lophotrichous: many (tuft) at one end of cell
4) peritrichous: around entire periphery of cell
What are the three parts of a bacterial flagellum?
1) filament
2) hook
3) basal body
How do flagella grow?
-flagellin molecules pass through channel in filament and incorporated at terminus, thus growing from tip
Describe the filament part of a flagella.
-rigid, helically-shaped polymer of identical protein subunits known as flagellin
Describe the hook of the flagella.
-a different protein that connects the filament to the motor portion (basal body)
Describe the basal body
composed of a rod that passes through two (G+) or four (G-) rings that anchor flagellum to membrane
-surrounding the inner ring are the motor (mot) proteins and the switch (Fli) proteins
How do flagellum move bacteria?
-they spin like a propeller
-increasing or decreasing rate of rotation affects speed and direction
-CCW is a run, CW is a tumble
Where does energy for teh basal body "motor" come from?
-derived from protonmotive force
What are eukaryotic flagella composed of?
-microtubules (bundles of tubulin)
-dynein (motor)
How does the flagella move a eukaryote?
-in a whip-like motion caused by microtubule sliding
How does cilia work?
-since it's shorter and more numerous than flagella, they beat like oars

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