Passive And Active Transport Flashcards
What is a facilitative transporter
A transmembrane protein that changes its shape when the solute binds to it
It then exposes the solute to the other side (where there’s less concentration of solute)
What happens to the rate of transport for facilitative transporters when the concentration of solute is high
The rate of solute transport levels off, it doesn’t keep increasing
Too saturated to keep increasing the rate of trnasporg
How many ions per second do ion channels transport
How many molecules for facilitative transporters
Millions
100-1000
What is an example of a facilitative transporter
How does it work
The glucose transporter GLUT4
The glucose is continuously diffused into the cell because it’s phosphorylated
It’s bidirectional (it transports into and out of cell based on solute concentration)
What are the differences in the
rate of transport,
type of solute,
conformational change, and
direction of transport
for channels and facilitative transporters
REST ON D2L
Conformational: Channels are open of gated (closed) depending on voltage, ligand, mechano
Facilitative transporters change in response to solutes binding
Why is active transport needed
Is it selective?
Needed to make steep concentration gradients across the plasma membrane
It is selective, transports specific substrates
What does active transport require
How does it get it
Needs energy input to transport
Get through hydrolysis of atp (primary active transport)
Or flow of other solutes down their concentration gradients (secondary)
What are the three type of pumps used in primary active transport
P-type pump
V-type pump
ABC transporters
What is the p-type ion pump and what is an example of one
It becomes phosphoylated during active transport
Na/K-ATPase is an example (sodium potassium pump, ATPase turns ATP to ADP)
It helps maintain the membrane potential (voltage) in cells
For the sodium potassium pump, whats pumped in and pumped out per 1 atp
3 Na+ pumped out
2 K+ pumped in
What happens if there are defects in the sodium potassium pump
There are impacts on endocrine system, hypertension, neuromuscular disorders, seizures, etc.
What happens on step 1 of the p type pump
The pump is in the E1 conformation (it’s binding sites are open to the inside of the cell)
It has a high affinity for NA ions, has three binding sites for them
Atp is bound to the pump
What happens in step 2 of the p type pump
The na ions are bound to the three sites in the pump, so the pumps closes (occluded) so ions don’t flow back out
What is steps 2-3 of p type pump
Atp is hydrolized to give adp and phosphorus on the pump
Pump phosphorylated
What is steps 3-4 of the p type pump
Adp is released from the pump and the pump chafe to E2 conformation with P still on it
The ion binding sites are accessible on the outside of membrane
It loses affinity for NA and now wants K (has 2 binding sites for it)
What are steps 5-6 of the p type pump
When the k ions are bound, the pump closes (occluded E2 state)
The phosphorus falls off (pump is dephospohrylated)
What are steps 7-8 of the p type pump
Atp binds to the pump and the protien goes back to E1 conformation
Realeased k ion into cell
Now has low affinity for k ions and high for na
Is the transport through the p type pump faster than through ion channels?
No, the p type pump does many conformational changes to transport so the rate of transport is much slower
What another example of a p type pump
How does it work
H/k atpase
Pumps protons into extracellular space in the stomach
Pumps k in
What are vtype ion pumps
They use atp energy to transfer solutes but they don’t get phosphorylated
They transport hydrogen ions across organelles and vacuoles (this helps in keeping the low ph of lysosomes)
Found in the plasma membrane of some cells (play roles in keeping acid base balance in kidney tubules)
What are ABC transporters
ATP-Binding cassette transporters
Have a similar atp binding domain to the p type ion pump
These help transport ions, lipids, peptides, and nucleosides in mammals
What is secondary active transport
Doesn’t use atp directly as energy source, it uses the potential energy from concentration gradients
The concentration gradient across the memebrane is a form of stored (potential) energy
What is a symporter
A type of secondary active transport where two substances are moved in the same direction
Also called cotransporter
In this , one substance moves with is concentration gradients which gives the energy for the other to move against is gradient in the same direction
What is an anti porter
Type of secondary active transport where two substances are moved in the opposite direction
Also called exchanger
In this , one substance moves with is concentration gradients which gives the energy for the other to move against is gradient in the opposite direction
Hat is an example of a symport secondary active transporter
The na/glucose transporter
It moves glucose from the intestinal lumen into the epithelial cells. The concentration of glucose in the cell is already high so this is against the gradient
Na ions are moved into the cells as well but the concentration of na in cells is low so this is with its gradient
This an transport makes the energy for glucose to be transported
Is the na/glucose symport, what type of transport does na to to make the na gradient in the first place
Primary active, p-type
