lecture 13

Question 1

What is lateral diffusion?

Answer 1

the horizontal movement of lipids or proteins across the membrane

Question 2

What is transverse diffusion?

Answer 2

the flip flopping of lipids or proteins across the membrane surface

Question 3

What is the FRAP experiment?

Answer 3

fluorescence recovery after photobleaching
1. lipids/proteins are labelled with fluorescent molecules
2. black fluorescence in a defined area with laser
3. monitor recovery within bleach

Question 4

What is a flippase?

Answer 4

lipid transporter protein that moves unidirectional, hydrolyzing ATP
P ATPase(outside to inside)

Question 5

What is a floppase?

Answer 5

ABC transporter (inside to outside)
requires 2 ATP
unidirectional

Question 6

What is a scramblase?

Answer 6

no energy required, driven by concentration gradients

Question 7

what is the difference between integral and peripheral membrane proteins?

Answer 7

integral proteins span the entire membrane and make contact witubtxe hydrophobic region the bilayer, they can be released with strong detergents.
Peripheral proteins are intact with the exposed surfaces and can be dissociated by high salt or change on PH

Question 8

What is an annular lipid?

Answer 8

bind/stick to membrane proteins, acyl side chains and lipid polar head to form salt bridges/HB w protein residues, provide smooth surface for bulk lipids and are self sealing

Question 9

What is a lipid raft?

Answer 9

cholesterol and sphingolipids that form micro domains on plasmas membrane, allow for cell signaling and membrane budding

Question 10

What is the structure, property and localization of fatty acylated proteins?

Answer 10

myrisate: linked to GLY on protein N-term, found on cytoplasmic side
palmitate: thirster linkage to CYs, protein head with thirster and ketone
Important for raft association of integral membrane proteins

Question 11

What is the structure, property and localization of prenylated proteins?

Answer 11

farnesyl or geranyl thioester linkage to cis near C term
protein attached to sulfur then chain
in inner leaflet, no raft

Question 12

What is the structure, property and localization of GPI anchored proteins?

Answer 12

phosphoethanolalmine head connected to phosphate, tetrasaccharide and a phosphatidyl inositol
outer leaflet of plasma membrane, form raft

Question 13

What is caveolin?

Answer 13

associates with lipid rafts and promotes plasma membrane curvature
forms dimer, multi palmitoylated, binds cholesterol, promotes membrane curvature

Question 14

What are the properties of the cytoskeleton?

Answer 14

spectrin and actin form long filaments on cytosolic side if membrane that anchor specific membrane protein
increase surface area to allow rapid diffusion of O2 across membrane to Hb
biconcave disk

Question 15

How does the membrane composition impact the membrane fluidity?

Answer 15

more shorter, unsaturated chains is more fluid and decrease melting temp
more long, saturated chains are less fluid and have a high melting point

Question 16

What are the four types of integral membrane protein

Answer 16

1 strand-polar backbones expose din hydrophobic environment
1-a helix:hydrophobic sidehchain to hydrophobic side
multiple a helices
B-barrel: in outer membrane of bacteria, chloroplast and mitochondria

Question 17

What are properties of the two asymmetric bilayers