L26- Membrane Lipids Flashcards
What is the structural difference between phospholipids and glycolipids?
Phospholipids have a charged phosphate group attached to their backbone whereas glycolipids contain an O-linked sugar.
Which molecule(s) make up the backbone of phospholipids?
Either glycerol or sphingosine.
Which molecule(s) make up the backbone of glycolipids?
Sphingosine.
The phosphate group in glycerophospholipids is bound in what type of bond?
Phosphodiester bond.
What are the five alcohol head groups of glycerophospholipids?
Serine, choline, ethanolamine, inositol and glycerol.
In glycerophospholipids, the glycerol backbone is typically linked to fatty acids in what type of bond?
Ester bond.
What is the name of the glycerophospholipid that contains a phosphate on its third carbon but no alcohol head group?
Phosphatidic acid (PA).
What is the structural difference between a membrane phospholipid such as lecithin and lung surfactant (dipalmitoyl phosphatidyl choline)?
Lecithin has a saturated fatty acid at C1 and an unsaturated fatty acid at C2, which is important for membrane fluidity. Surfactant has a saturated fatty acid at both C1 and C2. This makes surfactant more rigid than lecithin, allowing it to hold lung alveoli open (by reducing surface tension at the air-water interface).
What is respiratory distress syndrome?
The absence of lung surfactant in premature infants (typically infants born before 28 weeks of gestation).
In order to add a third fatty acid to phosphatidic acid, what molecule is required to activate either the hydroxyl of a head alcohol group or the hydroxyl on C3 of glycerol?
CTP (note that two phosphate are released in this activation, resulting in the attachment of CMP to phosphatidic acid).
Formation of glycerophospholipids requires activation of either glycerol or the alcohol head group. Which glycerophospholipids are synthesized by activating the OH group on glycerol?
Phosphatidyl inositol (PI), phosphatidyl glycerol (PG), and cardiolipin.
Formation of glycerophospholipids requires activation of either glycerol or the alcohol head group. Which glycerophospholipids are synthesized by activating the OH on the alcohol head group?
Phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE).
Which glycerophospholipid is a prominent component of mitochondrial inner membranes?
Cardiolipin.
How is the structure of cardiolipin different than that of other glycerophospholipids?
While most glyerophospholipids have fatty acids linked to C1 and C2 of glycerol via ester linkage, cardiolipin has phospholipids linked to C1 and C3 of glycerol via phosphodiester linkage.
Phosphatidyl serine (PS) cannot be directly synthesized from activation of either the serine head group or the C3 hydroxyl of glycerol. How is PS synthesized?
Ethanolamine on PE is enzymatically interconverted with a serine to form PS. Note that this is the only pathway for the formation of PS in mammals.
Triple methylation of phosphatidyl ethanolamine (PE) by S-adenosyl mathionine (SAM) yields which glycerophospholipid?
Phosphatidyl choline (PC).
Decarboxylation of phosphatidyl serine (PS) yields which glycerophospholipid?
Phosphatidyl ethanolamine (PE).
True or False. Phosphatidyl ethanolamine (PE) can be formed by condensing CDP-ethanolamine to either phosphatidic acid (PA) or diacylglycerol (DAG).
True.
Name two physiologically important ether-linked glycolipids.
Platelet activating factor (PAF) and plasmalogens.
Which enzyme hydrolyzes the fatty acid on C1 of glycerophospholipids?
Phospholipase A1.
Which enzyme hydrolyzes the fatty acid on C2 of glycerophospholipids?
Phospholipase A2.
Which bond in glycerophospholipids is hydrolyzed by phospholipase C?
The phosphodiester bond on the glycerol side of the molecule.
Which phospholipase plays an important role in the generation of intracellular secondary signaling molecules?
Phospholipase C.
Which phospholipase regenerates phosphatidic acid (PA) by removing the free alcohol head group?
Phospholipase D.
