Triacylglycerides and Phospholipids Flashcards
what is the structure of a TAG?
glycerol esterified to 3 FAs. The FAs are generally not the same, the first FA is usually saturated and the second FA is unsaturated and the third can be either
describe the storage of TAG
they are hydrophobic and cannot form micelles so instead the form oily, anhydrous droplets in adipocytes
glycerol phosphate is the initial precursor for TAGs, where does it come from?
2 pathways: 1) the liver and adipose tissue using reactions of glycolysis, glucose is converted into DHAP and glycerol phosphate dehydrogenase converts DHAP into gylcerol phosphate 2) only in the liver glycerol kinase converts free glycerol into glycerol phosphate
describe the synthesis of TAG from fatty acids and glycerol
2 steps: 1) generation of FA-CoA from FA and the enzyme FA-CoA synthetase uses CoA and ATP to form FA-CoA. 2) a series of 4 reactions occurs: first the addition of fatty acyl-CoA and second the addition of fatty acyl-CoA removal of the phosphate group and third the addition of fatty acyl-CoA
describe the different fates of TAG in the liver, intestine, and adipose
adipose: clustered in anhydrous droplets within the cytosol where it serves as a fat depot
liver: liver does not store fat, it secretes it with cholesteryl esters, cholesterol, phospholipids, and proteins such as apolipoprotein B100 in the form of VLDL, which go into the blood and deliver endogenous lipids
intestines: package lipids in chylomicrons
what are the two classes of phospholipids?
glyercophospholipids (glycerol backbone), sphingolipids (contain sphingosine)
discuss the structure of glycerolphospholipids
all contain phosphatidic acid (diacylglycerol with phosphate group) different units especially alcohols can bind the phosphate group to create different relevant products
cardiolipin
constructed in the mitocondria and contains two molecules of phosphatidic acid which are esterified to a common glycerol through their phosphtate groups. it forms an important part of the inner mitochondrial matrix and it is the only glycerophospholipid known to be antigenic, as Abs against syphylilis will react with cardiolipin
how is phosphatidic acid formed?
phosphatidic acid is formed through the same pathway as TAG, except without the removal of the third phosphate group for another acyl ester
describe the synthesis of glycerophospholipids
2 pathways result in the combination of a diacyglycerol with an alcohol, the two mechanisms separate which reactant is bound to CDP, which becomes activated intermediate, when they combine and release CMP, synthesis occurs in the smooth ER and are sent to the Golgi
what is sphingomyelin
sphingomyelin is a 3 carbon backbone alcohol and fatty acid attached to 1C amine group with a fatty acid attached to middle C phosphorylcholine group attached to the last C part of the PM with high affinity for cholesterol and an important part of myelin
what is ceramide?
ceramide is part of sphingomyelin (without the phosphorylcholine) and there are 2 fates: 1) it can become sphingomyelin vai attachment of phosphorylcholine 2) C3 alcohol links with glucose or galactose and becomes precursors for phospholipids
describe the degradation of phosphoglycerides
done by phospohlipases destroying the ester bonds removal of the FA from C1 or C2 creates a lysophophoglyceride, which are substrates for lysophospholipaseses, phospholipases can cuase the release of messengers (DAG and IP3) and also can selectively remove specific FA for replacement with another FA via a transferase
describe the degradation of sphingomyelin
done by spingomyelinases to form ceramide, which is degraded by cermidase into a FA and sphingosine
describe Niemann-Pick Disease
NPC disease is a lack of sphingomyelinase, which means it cannot be broken down, there is enlargement of the spleen and uncontrolled sphingomyelin deposits placed in the CNS which cause infant death with Type1, Type2 affects the spleen, liver, lungs, and bone marrow more frequently
