Lecture 14 - Membrane structure Flashcards
what are membranes composed of?
lipids and proteins
True or False:
Membranes vary in their lipid:protein ratio
True
What’s the lipid:protein ratio of the plasma membrane?
equal
What type are most lipids?
glycerophospholipids
What are glycerophospholipids made of?
1) glycerol 3-P (simple carb)
2) 2 fatty acid acyl chains (with acyl gps)
3) extra gp attached to phosphate gp
1) What’s an acyl gp?
2) What’s the purpose of the extra gp?
3) which part is hydrophobic, non-polar?
4) which part is hydrophilic, polar?
1) FA without its hydroxyl gp at its carboxyl terminal
2) gives it it’s special character; unique
3) tail
4) head
What is a cardiolipin?
two glycerophospholipids bridged together at the top by another glycerol gp
What is the name of one of the most important lipids as far as metabolic regulation?
What does it have to make it unique?
What is it used in in relation to metabolism?
Phosphatidylinositol
Insoitol ring at the top bonded to P gp –> inositol ring can be phosphorylated
used metabolically in signaling processes
Name the major FA in membrane lipids = # of Cs, if its saturated or unsaturated and # of dbl bonds
1) Palmitic acid = C16, saturated
2) Stearic acid = C18, saturated
3) Oleic acid = C18, cis unsaturated, 1 dbl bond
4) Linoleic acid = C18, cis unsaturated, 2 dbl bonds
5) Linolenic acid = C18, cis unsaturated, 3 dbl bonds
6) Arachidonic acid = C20, cis unsaturated, 4 dbl bonds
True or False:
Lipids are stationary rigid structures.
False
Lipids are wobbling around, rotating around
What do double bonds do for the FA
Name the two forms
give the FA additional structure
Cis dbl bond - puts kink in structure
Trans dbl bond - makes more rigid
What is a sphingosine?
What is it made of?
one of the special gps that can be attached to a FA
top gp with a long non-polar FA tail; add gps to sphingosine to make shingolipids
What’s a sphingolipid
What’s a ceramide?
What’s a sphingomyelin?
What’s a glycosphingolipid?
What’s a cerebroside?
Sphingosine with an additional FA gp
a sphingolipid
sphingolipid with a choline gp attached at the top to the phosphate gp
sphingolipid with a sugar attached at top
a glycophingolipid with specifically a galactose attached at the top –> interact with water better; signaling
Describe cholesterol and its relation to membrane structure
1) Cholesterol has lots of hydrophobic parts that point down
2) has a hydroxyl gp that sticks out which makes it polar and is also the attachment site for other functional gps/mols; it also adds character to the mol
3) Cholesterol is incorporated into the membrane
Describe lipid compositio in membranes
1) varied lipid composition in different membranes
2) mainly glycerophospholipids
3) individual phospholipid categories - mainlyphosphatidylcholine
Describe phospholipid distribution btw inner and outer layers of phospholipid bilayer
Name three enzymes involved with the phospholipid bilayer and thir function
Lipids on outer leaflet have a different composition that lipids on inner leaflet (cytoplasm)
Flippase, Floppase, Scramblase - responsible for generating and maintaining composition of bilayer
Name and describe membrane proteins
1) Integral membrane/transmembrane proteins - proteins that pass through entire membrane
2) Peripheral membrane proteins - connected to one side of lipid bilayer –> associate through charges (AA side chains, polar head gps) or some sort of lipid
*interact with other membrane proteins
True or False:
transmembrane alpha helixes predicted by side change hydrophobicity
True
where there’s more hydrophobic AAs –> more likely to form transmembrane proteins
What’s an aquaporin?
membrane protein that allows water to pass through the membrane; in center is the core that allows water to pass
Name the three different ways a peripheral membrane protein can attach to the membrane
1) By a oligossacharide - COOH gp
2) by covalent bond between N of protein and C of lipid
3) by a cysteine side chain - sulfhydril bond
Explain how temperature can affect membrane lipid motion
Explain affect of dbl bonds on nmotion
1) Above transition temperature - swinging around very rapidly
2) below transition temperature - motions cease
3) nature of tails influence motion (presence of cis/trans dbl bonds)
4) more trans dbl bonds = less motion; more cis dbl bonds = more motion
5) proteins are the structures doing the functions –> must maintain that motion to function effectively
1) define membrane fluidity
2) Discuss membrane fluidity
3) What are the primary factors
4) what does increased membrane cholesterol content affect?
5) what does altering membrane fluidity affect?
1) indicates the relative rates of motion of the lipid constituents
2) it is a function of the composition of the membrane
3) FA chain length, extent of saturation and cholesterol content are primary factors
4) increased membrane cholesterol content during disease affects fluidity
* so can presence of foreign mols like ethanol
*so can lipid peroxidation
5) altering membrane fluidity in turn can alter the function of the proteins embedded in the membrane
What are microdomains?
What’s another name?
What are they made of?
certain proteins attract certain types of membrane constituents
rafts –> lipid rafts attracted to particular proteins (float around)
cholesterol and sphingolipids
