Membrane and Gas Transport Flashcards
What kind of molecules can pass directly through the phospholipid bilayer?
Lipid soluble molecules
What molecules have to be transported across the phospholipid bilayer?
Charged, polar molecules or large molecules
What are the three main types of membrane transport?
Simple diffusion, facilitated diffusion, and active transport
simple diffusion
Diffusion of molecules through the cell membrane or through an open channel. Goes down the concentration gradient until system reached equilibrium.
In general, what is Fick’s law?
Fick’s law is an equation that describes the rate at which a substance can flow down its gradient. (I.e., how quickly it move from one compartment to another or how easily a solute can pass through a membrane).
What factors can influence net flux?
Electrical gradient, temperate, surface area, mass, and membrane permeability.
What kind of relationship does Fick’s law represent?
A linear relationship. As the permeability of the membrane increases, the flux increases.
Partition Coefficient
relates how well a substance will partition itself between two I miscible substances. Basically, will it stay between them or does it prefer water or lipid?
How do you calculate the partition coefficient?
Concentration of substance in oil/concentration of substance in water
Partition coefficient=1
Exists equally in water and oil
Partition coefficient>1
Lipophilic (soluble in oil) and can pass easily through the membrane.
Partition coefficient
Only soluble in water and will not easily pass through the membrane
Pore
Non gated transmembrane protein channel that is always open. Transports according to the concentration gradient.
Channel
Gates transmembrane protein that can open and close
Transporter
Transmembrane protein that undergoes a conformational change and facilitates the transport of a “packet of substrate across the membrane.
What do ion channels do?
They increase the permeability of the membrane for that ion species.
What are the three types of ion channels?
Ligand gated-activated with a specific molecules binds to the binding site causing a conformational change.
Voltage gated-a change in the membrane potential causes the molecules to move within the channel.
Mechanosensitve-whole stretch of the membrane that may affect the channel conformation by either opening or closing the channel.
What are the four major factors that determine the rate of transport across a membrane?
Saturation of transporter
Number of transports
Conformational change (takes time to change shape)
Gradient
Facilitated Diffusion
Solute is moved across a membrane down its electrochemical gradient. Transporters are specific for a substrate.
Active Transport
requires an energy source to move a solute against its electrochemical gradient (which can generate voltage). that energy source is usually ATP
what is the difference between primary active transport and secondary active transport?
In primary, the concentration gradient is used to move a solute against its own gradient, n secondary it moves another solute against its concentration gradient.
Co-transporter
In secondary active transport in which both substrates are moved in the same direction
Exchanger
In secondary active transport in which the two substrates move in opposite directions.
Anti porters
Another name for secondary active exchangers, these utilize the electrochemical gradient of one substrate to drive another substrate in the opposite direction.
