Passive And Active Transport

Question 1

What is a facilitative transporter

Answer 1

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)

Question 2

What happens to the rate of transport for facilitative transporters when the concentration of solute is high

Answer 2

The rate of solute transport levels off, it doesn’t keep increasing

Too saturated to keep increasing the rate of trnasporg

Question 3

How many ions per second do ion channels transport

How many molecules for facilitative transporters

Answer 3

Millions

100-1000

Question 4

What is an example of a facilitative transporter

How does it work

Answer 4

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)

Question 5

What are the differences in the
rate of transport,
type of solute,
conformational change, and
direction of transport
for channels and facilitative transporters

Answer 5

REST ON D2L

Conformational: Channels are open of gated (closed) depending on voltage, ligand, mechano
Facilitative transporters change in response to solutes binding

Question 6

Why is active transport needed

Is it selective?

Answer 6

Needed to make steep concentration gradients across the plasma membrane

It is selective, transports specific substrates

Question 7

What does active transport require

How does it get it

Answer 7

Needs energy input to transport

Get through hydrolysis of atp (primary active transport)

Or flow of other solutes down their concentration gradients (secondary)

Question 8

What are the three type of pumps used in primary active transport

Answer 8

P-type pump
V-type pump
ABC transporters

Question 9

What is the p-type ion pump and what is an example of one

Answer 9

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

Question 10

For the sodium potassium pump, whats pumped in and pumped out per 1 atp

Answer 10

3 Na+ pumped out

2 K+ pumped in

Question 11

What happens if there are defects in the sodium potassium pump

Answer 11

There are impacts on endocrine system, hypertension, neuromuscular disorders, seizures, etc.

Question 12

What happens on step 1 of the p type pump

Answer 12

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

Question 13

What happens in step 2 of the p type pump

Answer 13

The na ions are bound to the three sites in the pump, so the pumps closes (occluded) so ions don’t flow back out

Question 14

What is steps 2-3 of p type pump

Answer 14

Atp is hydrolized to give adp and phosphorus on the pump

Pump phosphorylated

Question 15

What is steps 3-4 of the p type pump

Answer 15

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)

Question 16

What are steps 5-6 of the p type pump

Answer 16

When the k ions are bound, the pump closes (occluded E2 state)

The phosphorus falls off (pump is dephospohrylated)

Question 17

What are steps 7-8 of the p type pump

Answer 17

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

Question 18

Is the transport through the p type pump faster than through ion channels?

Answer 18

No, the p type pump does many conformational changes to transport so the rate of transport is much slower

Question 19

What another example of a p type pump

How does it work

Answer 19

H/k atpase

Pumps protons into extracellular space in the stomach

Pumps k in

Question 20

What are vtype ion pumps

Answer 20

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)

Question 21

What are ABC transporters

Answer 21

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

Question 22

What is secondary active transport

Answer 22

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

Question 23

What is a symporter

Answer 23

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

Question 24

What is an anti porter

Answer 24

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

Question 25

Hat is an example of a symport secondary active transporter

Answer 25

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

Question 26

Is the na/glucose symport, what type of transport does na to to make the na gradient in the first place

Answer 26

Primary active, p-type