Biochemistry - Membrane Lipids Flashcards
Are sphingolipids amphiphatic?
Yes.
Describe the basic structure of glycerophospholipids.
Glycerol backbone usually with a saturated FA on C1, and unsaturated FA on C2, and an alcohol group on C3 via a phosphodiester linkage.
What is cardiolipin and where is it found?
It is a glycerophospholipid with two phosphate groups and is commonly found on mitochondrial membranes.
Which membrane (outer vs. inner) is phosphatidyl choline (PC) usually found?
Outer.
Which membrane (outer vs. inner) is phosphatidyl ethanolamine (PE) usually found?
Inner.
Which membrane (outer vs. inner) is phosphatidyl serine (PS) usually found?
Inner.
Which glycerophospholipid, when found on the outer membrane, is a potent signal for apoptosis?
Phosphatidyl serine (PS)
What is unique about glycerophospholipids found in lung alveoli?
The C2 FA is saturated to prevent alveolar collapse.
Which glycerophospholipids can be interconverted?
- PE to PS (only way in humans to make PS).
2. PE to PC via methylation
What is a plasmalogen? What are two important functions of these molecules?
A glycerophospholipid with a fatty alcohol in an ETHER linkage at C1.
Functions:
- Platelet-activating factor is a plasmanyl (no double bonds vs plasmenyl has 2x bond)
- Found on the mitochondrial inner membrane because they are resistant to oxidative damage that could potentially hydrolyze ester bonds.
What do phospholipases do?
They cleave bonds of glycerophospholipids to create signaling molecules.
What do PLA2s do?
Cleave PUFAs off glycerophospholipids. The PUFAs are then acted upon by oxygenases to create intercellular signaling molecules.
Are PLAs found in venom? What cells do they mess with?
Yeah. They act as hemolytic detergents against RBCs.
Name an important FA that is involved in intercellular signaling via phospholipase A2s.
Arachidonic acid.
What enzyme acts upon arachidonic acid to generate prostaglandins?
Cyclooxygenase
What two important chemical changes occur when arachidonic acid is reacted to form prostaglandins by cycloxygenase?
Double bonds are lost and a cyclic molecule is the result.
What does the “2” in prostaglandin G2 indicate?
It indicates the remaining number of double bonds (arachidonic acid, its precursor, has 4 double bonds)
What do lipooxygenases do? What chemical change occurs?
Make leukotrienes from arachidonic acid. Peroxide is added (note: no change in double bonds)
What does the “5” in 5-lipooxygenase mean?
It indicates which carbon will have the peroxide added.
What are the three places lipooxygenases can add peroxides to arachidonic acid?
5, 12, 15
Are leukotrienes linear molecules?
Yes.
How are PIPs created?
Phosphorylation (by a kinase) of phosphatidyl-inositol.
What do PLCs do?
They cleave IPs (inositol phosphates) off phosphatidyl inositol WITH the phosphate group.
What does IP3 do?
It is a second messenger molecule that results in release of Ca2+ from the ER, activating protein kinase C and calmodulin kinase.
