Lecture 17-18: Membrane Transport Proteins Flashcards
P type ATPase quick description/examples
Self phosphorylates
SERCA
Na/K pump
ABC transporter examples
ATP binding cassette
- MDR protein - monomer
- MsbA - homodimer
V type pump
Uses ATP
F type pump
Makes ATP
A/Actuator domain
Links the cytosolic domains to the transmembrane domains
N/Nucleotide binding domain
Binds ATP
P/Phosphorylation domain
Accepts the phosphate from ATP
SERCA steps
- E1 state, unphosphorylated, calcium ions bound
- ATP binds, calcium ions trapped
- ATP hydrolysis, self phosphorylation
- Eversion to E2 (open outside), Ca released
- Release of phosphate
- Eversion back to E1
Na/K steps
E1, Na ions bound, ATP bound Na ions trapped ATP hydrolysis, self phosphorylation Eversion to E2, Na ions released Binding of K K ions trapped, release of Pi, ATP rebinding Eversion to E1 Release of K
ABC transporter steps
- Empty transporter
- Small molecule binds and is trapped, ATP binding site affinity increases
- 2 ATPs bind causing eversion
- Small molecule is released
- ATP hydrolysis and release
What type of transport does the Na/Glucose cotransporter use
Secondary active transport
T or F: All secondary transporters are symporters
True
Steps of lactose permease and type of transport
Secondary active transport
- Empty carrier, H+ binds and increases affinity for lactose
- Lactose binds
- Eversion
- Lactose released
- Deprotonation
- Eversion
Factors effecting diffusion rates
Magnitude of concentration gradient Size of molecule Surface area/volume ratio (shape) Temperature Density of solvent Solubility of solute Distance to destination
What happens to speed of diffusion if surface area/volume ratio is higher
Faster
What does the movement in bacterial K+ channel result from
Electrostatic repulsion
3 ways to gate a channel
Voltage
Ligand
Stress
Do gap junctions have a specificity channel
No
2 Important pieces of ion channels
Selectivity filter
Gate
How do digitalis and ouabain work
They block the dephosphorylation event in the Na/K pump when the pump is in E2 conformation
How are sodium ions unable to enter K+ transporter even though they are smaller
The energy needed to strip the water molecules from Na+ is too great. There are favorable bonds that will form when K+ is stripped of its water molecules but unfavorable with Na+
How do potassium ions travel so quickly through their transporters
Because of electrostatic repulsion. The positive charge of each new K+ ion pushes the previous one out
What causes gap junctions to close
High concentrations of Ca+ ions or low pH
