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What are transporters used for?
to get nutrients into the cell
How does water pass through the membrane?
Water can freely pass the membrane in both directions because it is small and weakly polar
What is facilitated diffusion>
Can only transport solutes down a gradient
What is active transport?
Can transport sollutes against the electrochemical gradient, uses energy (ATP)
If a substrate is uncharged, how is the gradient determined?
By the concentration gradient alone, not the electrochemical gradient
What is the main difference between transport and diffusion?
Transporters are saturable, so their rate has an upper limit based on how many transporters are in the membrane
How do multicellular organisms acquire nutrients?
In multicellular organisms, nutrients can be acquired by means of diffusion or facilitated diffusion
How are nutrients acquired in unicellular organisms, including prokaryotes?
In unicellular organisms, including prokaryotes, nutrients are usually acquired by active transport
Are transport systems specific?
Transport systems are highly specidic; a single molecules or a class of closely related molecules
How does facilitated diffusion work?
- The binding of the substrate on one side of the membrane induce a conformation change in the carrier in such a way that the carrier open to the other side. The concentration of te substrate is lower there
- The substrates is released and diffuse away from teh carrier
What are the 2 types of facilitated diffusion?
What are the 2 conformations of carriers?
Open in, or open out
What is the difference between carriers and chanels?
Carriers are substrate specific
How does active transport work?
When the protein is open to the side with the higher concentration of substrate, a phosphate binds to it and changes the shape, this pushes the substrate out of the protein, and allows something else to bind to it
What is a uniporter?
Transports one molecule at a time
What is an antiporter?
1 molecule in and 1 molecule out at the same time
What is a Symporter?
2 molecules in the same direction at the same time
What type of active transport is pmf-dependent?
What are the three types of active transporters in prokaryotes?
- Simple transport
- Group translocation
- ABC transport
What s simple transport?
Driven by the energy of the proton motive force
What is group translocation?
Cjemical modification of the transported substance driven by phosphoenolpyruvate
What is ABC transporter?
Periplasmic binding proteins are involved and energy comes from ATP
How is Simple transport done when respiration is possible?
ETC pushes protons out, a terminal electron acceptor is present, proton motive force is generated
How is simpe transport done when respiration is not possible?
- ATPases can be used to generate the pmt, ATPases work in reverse
- pmf-dependant transporter are smporter or antiporter that use the proton gradient
- Pmf can be used to generate a gradient of Na+ that is used by some transporters as a soure of energy
Where is a sodium gradient found and used?
Sodium gradient is apparent in sea water and is used by bacterias in the sea
What is an ABC transporter?
- ATP-binding cassette, 3 components:
- A membrane spanning protein, the active transport carrier (not a channel)
- An ATP-hydrolyzing proteins that provide the energy for active transport
- A substrate-specific binding proteins that has very high affinity for a specific substrate (or a class of substrtes)
Why is the high affinity important in the ABC transporter?
High affinity allows it to bind in very low concentration
Where is the binding protien for ABC transporter found in gram-negative bacteria?
In the periplasm
Where is the binding protein for ABC transporter foundin the gram positive bacterias?
Anchored in the cytoplasmic membrane
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