Flashcards in Membrane transport of small molecules, and the electrical properties of membranes Deck (31):
What is the intracellular concentration of Na+?
What is the extracellular concentration of Na+?
What is the intracellular concentration of K+?
What is the extracellular concentration of K+?
What is the intracellular concentration of Mg2+?
What is the extracellular concentration of Mg2+?
What is the intracellular concentration of Ca2+?
What is the extracellular concentration of Ca2+?
What is the intracellular concentration of H+?
What is the extracellular concentration of H+?
What is the intracellular concentration of Cl-?
What is the extracellular concentration of Cl-?
How does size effect a molecules chance of getting through the membrane?
The smaller the molecule the more easily it can pass through the membrane.
How does electrical charge effect a molecules chance of getting through the membrane?
It causes association with water, water crowds around the charge, it makes it so the membrane is basically completely impermeable to charged molecules due to water association.
How does lipid-solubility/polar vs non polar effect a molecules chance of getting through the membrane?
Non polar molecules travel easily through the membrane. Even large nonpolar entities can cross the membrane.
Rearrange in order of highest permeability to lowest. Polar small, ions, polar large, nonpolar (large and small).
Small and large nonpolar (all can cross), small polar, large polar, ions (none will cross).
How do ions cross a membrane?
Through membrane proteins.
How do channel proteins work?
They have a pore in their center which is shielded from the nonpolar nature of the membrane. This pore, sometimes made by incomplete alpha helices, provides a point water can enter, it also allows for the transport of ions through at a quick rate.
What are the units of flux rate (flux rate in its use of ions crossing through a single membrane protein)?
What is the flux rate of a channel protein?
10^7or8 ions per second. It has the fastest rate, since a channel protein has unrestricted flow through it's aqueous pore.
Transporter proteins, how do they work?
They bind with a higher affinity, to the substrate. They then toggle positions. So if the protein translated Ca2+ out of the cell, it would start open to the interior of the cell, calcium would come in and bind, It would shift to being closed to both the extra and intracellular space, then the extracellular space. Once in the extracellular formation the Ca2+ would no longer have the same affinity for the binding site (since the protein has shifted) it would leave allowing the protein to shift back the open to intracellular position.
What is a transporter enzymes average flux rate?
Differentiate between passive and active transport.
Passive requires no energy, movement is down concentration gradient. Active requires energy. Movement is against concentration gradient.
Primary active transport: (go for it)
Primary active transport is the process through which ATP is used to cause movement of Ions against their concentration gradients. An example is the Na+/K+ ATPase pump system.
When does simple diffusion become predominant over transport mediated?
Transport mediated will have a Km Vmax plot. While transport mediated will have this Vmax cut of point, passive diffusion will not, it will just be based on the magnitude of the concentration gradient.
-uniport (non coupled)
Uniport: one molecule is moved out or in
Symport: two different molecules are moved into the cell or out of the cell at the same time
Antiport: Two molecules are moved opposite directions at the same time.
Secondary active transport
Secondary active transport involves a non-ATP mediated energy source to drive transport against the membrane. This could be a coupled symport receptor where one molecule is being moved down its concentration gradient and the other is being moved against its concentration gradient. This could also be a light driven pump, go photosynthesis.
How is differential localization of transport proteins achieved?
Tight junctions: the protein will have segments that bind completely with each other, stopping movement of proteins through tight junction regions, and creating protein localization.
What is FRAP?
Fluorescence Recovery After Photobleaching
How does FRAP work?
You attach a Fluorescent dye to the proteins, you then with a laser bleach a segment of this dye (so it is no longer returning fluorescence). You measure the rate at which the fluoresced dye comes back to this bleached segment and the rate at which the bleached molecules spread out into the nonbleached. Basically we will see a gradual return of fluorescence to this location. We can measure that change and equate it to the rate at which these proteins diffuse through the membrane. Assuming we have already taken into account corrals.