Lecture 2.4: Membrane Transport Proteins Flashcards
What is the order of permeability for molecules?
ions, small hydrophobic, large uncharged polar, small uncharged polar
Most to least:
1. small hydrophobic (benzene, O2, CO2)
2. small uncharged polar (urea, glycerol, indole, H2O)
3. large uncharged polar molecules (glucose, amino acid tryptophan)
4. ions (Na+, K+, Cl-)
Molecules move [–] because energy is [–] as disorder [–]
spontaneously, released, increases
small hydrophobic molecules diffuse across the lipid bilayer from [–] to [–] concentration
high to low
simple diffusion (passive)
how do polar molecules cross the membrane?
hydration shell (solvation)
facilitated transport
ion dehydration is [–] and creates a [–] barrier
highly unfavorable and creates a kinetic barrier
Passive Transport
no external energy required
facilitated diffusion of molecules down a concentration gradient
active transport
external energy required
transport of molecules against a cocentration gradient
Channel Transporters
semi-selective
diffusion-controlled limit
no-saturation
carrier transporters
high specificity: binding & conformation change
slower than diffussion
saturation (max at high solute concentration)
What does the graph of [solute] vs translation rate look like for
Facillitated diffusion through a channel (passive)
linear
What does the graph of [solute] vs translation rate look like for
Facilitated diffusion through a carrier (passive)
hyperbolic
What does the graph of [solute] vs translation rate look like for
Active transport through a carrier
hyperbolic
if C(final) < C(initial) –> ∆G = [–] and is [–]
negative, exergonic, spontaneous
passive transport
if C(final) > C(initial) –> ∆G = [–] and is [–]
positive, endergoinc, nonspontaneous
active transport
amphipathic alpha-helices come together to form a [–] cavity in the membrane
hydrophilic
