Membrane Transport Flashcards
What percentage of membrane proteins are transport proteins?
15-30%
What sort of molecules need to use membrane transport proteins to permeate the membrane?
charged and partially charged molecules
What sort of molecules diffuse rapidly?
small, nonpolar molecules like O2 and CO2
what sort of molecules diffuse slowly?
small, polar molecules like urea and H2O
what prevents ions from diffusing through the membrane?
the degree of hydration and their charge
Ions and polar molecules diffuse through the hydrophobic portion of the membrane how?
membrane transport proteins
Are membrane transport proteins single or multi-pass?
multipass
What is a transporter?
AKA carriers or permeases, these membrane transport proteins bind to the specific solute, and change their shape to alternately expose one side of the membrane then the other to allow the ion to pass through
What is a channel?
form continuous pores that extend through the lipid bilayer which allows polar or charged molecules to diffuse down their concentration gradient
Which facilitates a faster rate o diffusion, channels or transporters?
channels
Why does active transport require energy from ATP?
because it moves molecules against their concentration gradients
what drives passive transport?
the molecule’s concentration gradient
What 3 things are true, regarding cations and anions, if the cell is negatively charged?
- the entry of cations is favorable
- the entry of anions is not
- the efflux of cations is not
What is the membrane potential?
a solutes concentration gradient and electrical potential difference across the membrane, forming the electrochemical gradient
what is voltage
electrical potential
which ions have a higher concentration outside the cell?
Na+, Mg2+, Ca2, and Cl-
which ions have a larger concentration inside the cell?
K+ and H+
What are the three Conformational orientations of the transporter proteins?
outward-open, occluded, inward-open
What are the three ways cells perform active transport?
coupled transport, ATP driven pumps, light-driven pumps
What is a is the difference between a antiport and a symport transporter?
A symporter brings the target molecules in the same direction (i.e. in or out of the membrane)
What is the key similarity between antiporters and symporters?
They use the concentration gradient of one molecule/ion to drive another molecule/ion against its concentration gradient.
At what ratio do Na-K pumps drive out Na+ ions to K+ ions?
3:2
Is the cell more acidic or less acidic than the extracellular environment?
slightly more acidic
How do cells generally regulate pH?
Na+-H+ exchangers
