Transport of Molecules Aross Membranes: Transporters & Ion Channels Flashcards
How do Transporters / Carriers transport molecules?
Through cycles of conformational changes
Do Transporters / Carriers have a high or low rate of transport?
Low
Do Uniporters transport molecules UP or DOWN their concentration gradients?
Down
How do Symporters and Antiporters transport molecules?
Couple the transport of one type of molecule UP its concentration gradient to the transport of another molecule(s) DOWN an electrochemical gradient
What is an example of a Uniporter?
GLUT1
* glucose transporter
What is an example of a Symporter?
Two-Na+ / One-Glucose Symporter
* transports Na+ DOWN its concentration gradient
* transports Glucose UP its concentration gradient
Why are TWO Na+ ions used in the Two-Na+ / One-Glucose Symporter?
- Transport of 2 Na+ provides twice as much energy
- Allows symporter to transport Glucose against a much steeper concentration gradient
What is an example of a Uniporter and Symporter working together?
2-Na+ / 1-Glucose Symporter + GLUT2 glucose uniporter
* work together to take up glucose from the gut
* 2-Na+ / 1-Glucose symporter in the microvilli transports glucose UP its concentration gradient from intestine into cells
* Glucose uniporter transports glucose into blood by facillitated diffusion
What are THREE Antiporters involved in regulating cellular pH?
- Na+ / H+ antiporter
- Na+ HCO3- / Cl- antiporter
- Cl- / HCO3- antiporter
How does the Na+ / H+ antiporter regulate cellular pH?
Exports H+ which Raises pH
How does the Na+ HCO3- / Cl- antiporter regulate cellular pH?
Imports HCO3- which Raises pH
How does the Cl- / HCO3- antiporter regulate cellular pH?
Exports HCO3- which Lowers pH
How is the opening/closing of Resting (Non-Gated) Ion Channels regulated?
Not regulated by any external factors
- open probability is an intrinsic property of the channel
How is the opening/closing of Voltage Gated Ion Channels regulated?
Regulated by the electrical potential across the membrane
* open probability depends on Vm (voltage across membrane)
How is the opening/closing of Ligand Gated Ion Channels regulated?
Regulated by binding of one or more ligands to channel
* open probability depends on ligand