Lipid Bilayer/Membrane Proteins

Question 1

speed of lateral diffusion

Answer 1

rapid, entropically favorable (incr disorder), polar heads don’t need to cross HPhob core

Question 2

speed of transverse diffusion

Answer 2

slow, polar heads need to travel across HPhob core

Question 3

flippases purpose

Answer 3

speed up transverse diffusion

Question 4

effects of temperature on diffusion

Answer 4

incr temp promotes fluidity, both lateral and transverse diffusion incr

Question 5

liquid crystal def

Answer 5

describes plasma membrane, substance that flows like a
liquid but has some degree of ordering in the
arrangement of its molecules

Question 6

permeability of molecules

Answer 6

charged molec less likely to pass, small uncharged molec pass easily

Question 7

hydropathy index

Answer 7

graphs free energy deltaG for moving AA from in the membrane (HPhob) to into water,
neg G = wants to leave membrane, not a stable transmembrane

Question 8

Bacteriorhodopsin structure

Answer 8

7 transmembrane helices

binds renitaldehyde w/Schiff base (covalent bond btwn Lys 216 and retinal)

Molecular switch which transforms light energy into a H+ electrochemical gradient w/ H+ pump

Question 9

Bacteriorhodopsin mechanism

Answer 9

H+ on the Schiff base is donated to Asp 85 and Asp 96 reprotonates the Schiff base

Question 10

Bacteriorhodopsin tense to relaxed

Answer 10

Schiff protonated, trans to cis photoisomerization, Schiff based closer to Asp85, Schiff base transfers H+ to Asp 85

Question 11

Porin structure

Answer 11

homotrimeric , each monomer 16 up/down B barrels

Question 12

Porin eyelet structure

Answer 12

loop connecting B5 and B6 extending into central open cavity

Question 13

Porin purpose

Answer 13

specificity for size of solutes that can tranverse the channel

Question 14

Porin aromatic belt

Answer 14

helps stab portein, has polar and HPhob character to interact w/HPhil/HPhob space of membrane , composed of aromatic AA