Channelopathies and Cell-to-Cell Communication Flashcards
How is equilibrium determined in terms of concentration of K+ and impermeable anions (M-) relative to extracellular fluid?
Equilibrium is determined by two opposing forces: a chemical gradient causes an ion (K+) to move down its concentration gradient, but this simulataneously creates an electrical gradient that opposes any further movement of the ion. This prevents any NET movement of ions.
What does active transport do? Where would you find active transport?
It moves substances against their electrochemical gradient.
In many cells, but especially in cells that need a lot of energy such as muscle and brain cells.
True or False: Cell membranes are phospholipid bilayers.
True.
What does a channel do as a functional type of membrane protein?
It allows diffusion through the membrane
What does a receptor doas a functional type of membrane protein?
It binds noncovalently with specific molecules initiating a change in membrane permeability or cell metabolism
What can a mutation in ion channel genes do? Give an example.
It can cause a loss or gain of a channel function.
Example: When the transmembrane conductance regulator (CFTR) is mutated in a condition known as Cystic Fibrosis, the protein functions as a channel for the movement of Cl- in/out of cells
What are the organs affected by cystic fibrosis?
Sinuses, lungs, skin, liver, pancreas, intestines and reproductive organs. Anything with epithelium.
What do carrier proteins do?
They never form an open channel between the two sides of the membrane, but instead, work like a rotating door. Facilitated diffusion.
Facilitated diffusion or active transport - which occurs and when?
It depends on the specific needs of a cell. Facilitated diffusion occurs across membranes of RBCs (for glucose concentration), while glucose is transported by active transport from the gut into intestinal epithelial cells.
What bacterium causes Cholera, and how does it kill?
It is caused by Vibrio cholerae and it kills by dehydrating the body (converts membrane osmolatiy to release more H2O)
How does cholera lead to dehydration?
It dehydrates due to the the movement of ions into the lumen. Cl- moves out of cells, drawing Na+ and H2O - ADP binds to G-proteins and creates a permanately active state, so it sends a never-ending signal to keep transporting out.
Describe the course of cholera.
- Purges Cl-
- Na+ doesn’t leak back into the cell.
- H2O rushes out of cells due to osmosis
- Death due to dehydration
What are sodium-dependent glucose cotransporters?
A family of glucose transporter found in the intestinal mucosa of the small intestine and the proximal tubule of the nephron (PCT of kidney)
How does glucose move into epithelial cells?
Na+ glucose transporters faciliate diffusion of glucose against concentration gradient. Add glucose to the solution. Na+ by itself cannot be taken into the intestinal cells, so adding glucose allows sodium-dependent glucose cotransporters (SGLT) to get Na+ into the cells.
What is the fight or flight response signaled by?
Epinephrine
