Composition/structure Flashcards
What are the major lipid components of the cell membrane? What is the most abundant of these?
Glycerophospholipids, sphingolipids, steroids.
Most abundant is glycerophospholipids.
How can the net charge of a phospholipid be determined?
The phosphate group will always have a -1 charge, so just determine the charge of the alcohol head group and sum them.
What is the structure of phospholipids?
Two long chain fatty acids bound to a glycerol backbone via ester bonds on C1 and C2, and a phosphate bound to C3 via an ester linkage.
If a lipid is unsaturated, where will the kinked acyl tail exist?
Most likely on C2
What are the two most common glycerophospholipids?
Phosphatidylethanolamine
Phosphatidylcholine
Together comprise 60% of the membrane lipid composition.
How does a sphingolipid differ from a phosphoglyceride (glycerophospholipid)?
The backbone is sphingosine (-NH- bridge connecting C2 to acyl tail) rather than glycerol (-O- bridge at. C2).
Describe a glycosphingolipid. What is a common one?
Attached to the phosphate, opposite to the spingosine, is a sugar residue. A common one is a GAG with multiple N-acetylneuraminic acid groups within it.
What is the general structure of cholesterol?
A four ring steroid structure with a hydrocarbon tail branching from the five membered ring.
What are the classes of membrane proteins?
Integral (cross membrane 1+ times) and peripheral (attached to an integral, have a short hydrophobic chain stuck in the membrane, or noncovalently bound to a PI inositol head group).
Describe a GPI.
A membrane PI has a glycan bound to its head group that protrudes into the ECM, and binds to a peripheral protein on its other side.
What factors affect membrane fluidity?
- Branchness of the acyl chain (double bonds increase fluidity).
- Acyl chain length (shorter tails are more fluid).
- Cholesterol content (less cholesterol means more fluid).
- Temperature (above Tm membrane is more fluid).
What moves membrane lipids from one side to the other?
Flippase- Outer leaflet to inner.
Floppase- Inner to outer.
Describe a lipid raft.
Enriched with cholesterol and sphingolipids. Acyl tails are also quite long, producing a bulge. This also decreases fluidity within the raft so it stays together.
GPI anchors are common in lipid rafts.
What is a caveolae?
Are lipid rafts containing peripheral protein caveolin on the inner leaflet that lead to invagination within the raft, and recruit/bind cholesterol within the raft too.
