Ion Channels and ECG

Question 1

what molecules can permeate a phospholipid membrane?

Answer 1

gases, small uncharged polar molecules, sometimes water

Question 2

what molecules cannot cross a phospholipid membrane without transporters?

Answer 2

large uncharged polar molecules, ions, charged polar molecules

Question 3

what are some characteristics of protein transporters?

Answer 3

protein is specific for molecule transported
protein binding site/channel may open/close
protein conformational change required

Question 4

what are energy sources for transporters?

Answer 4

ATP or concentration gradient

Question 5

what cells is Na K ATPase present in?

Answer 5

all cells

Question 6

how much of a cells ATP is used by Na K ATPase to establish ion gradients?

Answer 6

1/3

Question 7

what does Na K ATPase transport and where?

Answer 7

Na from cytosol to extracellular space

K from extracellular space to cytosol

Question 8

what are values of Km required to pick up a ligand?

Answer 8

Km lower than ligand conc.

Question 9

what are values of Km required to drop off a ligand?

Answer 9

Km higher than ligand conc.

Question 10

what are the steps of glucose transport from gut lumen through intestinal epithelium to blood?

Answer 10

1. Na K ATPase creates Na gradient so that the cytosol is Na depleted
2. Na glucose transporter allows Na to flow with gradient and drives glucose uptake from gut lumen against its gradient
3. glucose flows with gradient into blood through GLUT2
4. K channel allows K to flow with gradient to leave the cell