Polvi lec #5 Flashcards
In what movement (concentration gradient wise) does a facilitative transporter move mclcs?
It moves molecules from high conc to low conc still, as it’s still passive transport
How does a facilitative transporter move solute?
The binding of the solute triggers a conformational change in the transmembrane protein which then exposes the solute to the other side
What types of kinetics does facilitative transport exhibit? What does this mean? How does this make facilitative transporters different from ion channels?
They exhibit saturation type kinetics, this means that they plateau in their rate of solute movement when the solute concentration is high.
This makes their rate of transport slower than ion channels at (100-1000 mlcs per sec) compared to ion channels one million
What is GLUT4?
is a facilitative transporter, glucose binds to it, this triggers a conformational change, and glucose gets released into the cell.
How is continuous diffusion of glucose through GLUT4 possible?
Because the glucose is phosphorylated which makes the conc of glucose inside the cell low and allows conc outside of cell to be high.
How are facilitative transporters bidirectional?
Can move inside and can move outside of cell, just depends on conc gradient
What are the two types of active transport?
Primary transport and secondary transport
Why is active transport important for concentration gradients?
It’s required to create the steep concentration gradients across the plasma membrane that passive transport utilizes
What kind of proteins are involved in active transport?
Selective transmembrane proteins which undergo a change in conformation
What kind of energy input does primary transport need? What about secondary transport?
primary transport- needs breakdown of atp
secondary transport- needs the flow of other substances down their own conc gradient to provide energy for it’s own work
What are the three types of primary active transport?
P-type pump
V-type pump
ABC transporter
How does a P type pump work?
it moves solute through getting phosphorylated
What is a Na+/K+ pump? How does it work?
Is a p type ion pump, per atp molecule it uses it pumps out 3 Na+ and pumps in 2 K+
How it works:
Step 1- ion binding sites are open to inside of cell (transmembrane protein is in E1 confirmation), sodium enters transmembrane and atp binds
Step 2- The proteins becomes closed (occluded E1 state) when ions bind
Step 2-3- The bound ATP gets broken up and pump is phosphorylated (P still bound and ADP still bound)
Step 3-4- ADP gets released and protein open to outside of cell (E2 form of protein), gains K+ ions and releases Na ones
Step 5-6- K+ ions bind, the protein closes (occluded state) and the phosphate falls off
Step 7-8- ATP binds, proteins return to E1 confirmation and K+ gets released.
What is H+/K+ pump? Hows it work?
Is a P-type ion pump, is found in the lining of the stomach in cytoplasmic vesicle, when activated through food the vesicles fuse to the membrane and release H+ into stomach.
What are V-type ion pumps? How do they work? What are they responsible for?
V-type ion pumps are primary active pumps utilize ATP energy without becoming phosphorylated, they transport H ions in vacuoles and organelles, and are found in the plasma membrane of some cells.
They maintain the low ph of lysosomes, and have roles in maintaining the acid-base balance in kidney tubules
