Ion Channels and ECG Flashcards
what molecules can permeate a phospholipid membrane?
gases, small uncharged polar molecules, sometimes water
what molecules cannot cross a phospholipid membrane without transporters?
large uncharged polar molecules, ions, charged polar molecules
what are some characteristics of protein transporters?
protein is specific for molecule transported
protein binding site/channel may open/close
protein conformational change required
what are energy sources for transporters?
ATP or concentration gradient
what cells is Na K ATPase present in?
all cells
how much of a cells ATP is used by Na K ATPase to establish ion gradients?
1/3
what does Na K ATPase transport and where?
Na from cytosol to extracellular space
K from extracellular space to cytosol
what are values of Km required to pick up a ligand?
Km lower than ligand conc.
what are values of Km required to drop off a ligand?
Km higher than ligand conc.
what are the steps of glucose transport from gut lumen through intestinal epithelium to blood?
- Na K ATPase creates Na gradient so that the cytosol is Na depleted
- Na glucose transporter allows Na to flow with gradient and drives glucose uptake from gut lumen against its gradient
- glucose flows with gradient into blood through GLUT2
- K channel allows K to flow with gradient to leave the cell