Membrane transport, and the electrical properties of membranes

Question 1

P-type pumps

Answer 1

Use autophosphorylation (phosphorylate themselves) expending ATP to transport ions agains their electrochemical gradient.

Question 2

F-type pumps and V-type pumps

What does the V stand for?

Answer 2

These use the passive diffusion of H+ down it’s concentration gradient in order to fuel the production of ATP. vessicle.

Question 3

ABC transporters (ATP-Binding Cassette)

Answer 3

Use ATP hydrolysis to pump molecules against their electrochemical or concentration gradient.

Question 4

Sarcoplasmic Reticulum Ca2+ ATPase. (SR Ca2+ ATPase

Answer 4

Binds two Ca2+ ions from the cytosol. It then autophosphorylates an aspartic acid, resulting in the transport of 2 Ca2+ into the SR.

Question 5

What amino acid does SR ca2+ autophosphorylate?

Answer 5

Aspartic acid residue.

Question 6

Rheogenic means?

Answer 6

Generates an electric current across the bilayer.

Question 7

Electrogenic means?

Answer 7

Changes the voltage across the bilayer

Question 8

Na+ K+ pump is what pump type? is it Rheogenic? Electrogenic?
Ubiquitous?

Answer 8

P-type pump (autophosphorylates itself)

yes, yes, yes.

Question 9

Around what percentage of are ATP usage goes to Na+ K+ channel system?

Answer 9

~33% of a cells freakin energy…

Question 10

Are there examples of systems where the sodium potassium pump can run in reverse to generate energy?

Answer 10

Yes.

Question 11

Na K pump mechanism.

How does it function in regards to osmotic balance?

Answer 11

Three intracellular Na+ enter the pump, this allows the binding and autophosphorylation of Phosphate onto an aspartic acid residue. TBinding of phosphate alters structure, allowing 2 extracellular K+ to bind. This allows for dephosphorylation, which in turns causes a conformational shift which allows K+ to enter the cell, and prepares for Na+ to enter again.

Question 12

Ouabain does what?

Answer 12

Ouabain, stimulates Na/K ATPase at low level concentrations and blocks the pump at high concentrations.
It is also a naturally occurring hormone.

Question 13

Digitalis does what and comes from where?

Answer 13

Digitalis effects cardiac function by inhibiting the Na+-K+ATPase. This causes depolarization of the cell. It also results in a drop in efficacy of the Na+ Ca2+ exchanger, which results in an inability to properly regulate Ca2+, in a heart cell, which is a problem. Comes from Purple Foxglove.

Question 14

Na+/Ca2+ exchanger.

Answer 14

This is ran by an antiport mechanism which takes Ca2+ out of the cell and places Na+ back into the cell. It runs off of the Na gradient generated by the Na K pumps. So when Digitalis blocks the exchanger using cardiac glycosides like digitoxin and digoxin, problems happen.

Question 15

glycoside define:

Answer 15

A sugar bound to another functional group through a glycosidic bond.

Question 16

What are transport ATPases? (they are in gram negative bacteria)

Answer 16

They are transporter proteins imbedded in the cytosolic membrane of gram- bacteria.

Question 17

What does the ABC in ABC transporters stand for?

Answer 17

ATP binding cassette.

Question 18

What do ABC transporters do for bacteria?

Answer 18

They transport nutrients into the cell.

Question 19

Periplasmic substrate-binding protein is in what type of cell? What does it do there?

Answer 19

Periplasmic substrate-binding protein is in gram- bacteria, it binds specific solutes in the periplasmic space and brings them to the ABC transporter, which in bacteria means it will be transported into the cytosol.

Question 20

What is the periplasmic space?

Answer 20

The space between the two outer membranes of gram- bacteria.

Question 21

What function do ABC transporters serve in eukaryotes?

Answer 21

Transport of small molecules out of the cell. (generally toxic or waste)

Question 22

How much ATP is required to move a single solute through an ABC transporter?

Answer 22

2 ATP -> 2ADP

Question 23

Why are ABC proteins also known as MDR proteins?

Answer 23

MDR stands for multiple drug resistance. It’s because ABC transporters can transport out multiple toxic compounds from the cell, conveying resistance to multiple antibiotics/antifungals.

Question 24

How many transmembrane domains do ABC transporters have? How many alpha helices per transmembrane domain?

Answer 24

2

6

Question 25

Cystic Fibrosis Transmembrane regulator is an ABC protein, What type of mutation causes cystic fibrosis? How?

Answer 25

So the cystic fibrosis transmembrane regulator is an ABC protein which, when in it’s open configuration allow the flow of chloride down it’s electrochemical gradient. (which means it’s kind of evolved as a broken ABC protein, since normally ABC use ATP and active transport). Movement of CL allows for water to follow by osmosis (and Na, increasing osmosis). Both Cl and water are flowing out of epithelial cells on the lungs and accross other mucuos coated regions, the water dilutes the mucus. A single point mutation changes a single amino acid, this one change does not affect the the ability for the protein to work, but it makes it so the protein fails the bodies Ubiquitin protease quality check, the body then destroys the functioning protein, and membranes become covered with a thick mucus. This in the lungs is cystic fibrosis.