Synthesis of Fatty Acidy, Triacylglycerols and Phospholipids II Flashcards
Which enzyme is present in the liver that allows it to synthsize triacylglcerols from glycerol?
What product does this enzyme form?
Glycerol kinase
Glycerol 3-phosphate
What compound is reduced by adiose to produce glycerol-3-phosphate?
What does that tell us about when it is able to produce triacylglycerols?
DHAP
Adipose is only able to make triacylglycerols when glycolysis is active
Describe the process of triacylglycerol synthesis from glycerol-3-phosphate.
What are the 2 destinations for triacylglycerol?
- Glycerol-3-phosphate combines with 2 FattyCoA to form phosphatidic acid
- A phosphate is released to yield diacylglycerol
- a third FattyCoA is producign triacyl CoA
- Blood VLDL
- Adipose stores
Triacylglycerol is packed with which other structures to form VLDL?
What ist he major protein asosciated with VLDL?
cholesterol, phospholipids and proteins
major protein: apolipoprotein B-100 (apoB-100)
Draw this pathway
What are the 4 steps of synthesis, processing and secreting VLDL?
- Proteins are synthesized on RER
- Proteins are packages with triacylglycerols in the SER and Golgi Complex to form VLDL
- VLDL are transported to the cell membrane in vesicles
- VLDL are secreted via exocytosis
When do adipose cells produce lipoprotein lipase (LPL)? What does it do?
After a meal
digests triacylglyerols in chylomicrons and VLDL
What hormone stimulates both the transport of glucose into adipose cells and the synthesis and secretion of LDL?
insulin
What would be the effect of a defecivve LDL?
High blood triacylglycerl levels (from VLDL and chilomicrons)
During fasting, the decerase in insulin and the increase in glucagon cause which cellular regulator to increase?
Which does this stimulate within adipose tissue?
cAMP
stimulating lipolysis
Describe how cAMP stimulates lipolysis.
- increasing levels of cAMP stimulate PKA
- PKA phosphorylates hormons sensitive lipase (HSL) to its active form
- Adipose triglyceride lipase (ATGL) catalyzes the conversion of triglyceride to diglyceride + FA
- Activated HSL converts diglyceride to monoacylglycerol + FA
- monoglyceride lipase converts monoacylglycerol to glyerol + FA
- fatty acids and glycerol are released to the blood
Synthesis of glycerophospholipids
- Glycerol 3-P reacts with 2 activated fatty acids to produce phosphatidic acid
- Phosphatidic acid can then take 1 of 2 paths
-
Phosphatidic acid
- cleaved by a phosphatase to produce diacylglycerol
- diacylglycerol reacts with activated head group (CDP-choline/CDP-ethanolamine) to add the head group to the glycerol backbone
- produceing phosphatidylcholine or phosphatidylethanolamine
- *phosphatidylethanolamine can act with serine to produce phosphatidylserine
- *phosphatidylethanolamine can be methylated to produce phosphtidylchoine
-
Phosphatidic acid
- reacts with CTP to form CDP-diacylglycerol
-
CDP-diacylglycerol can react with two different substances
- inosatol to produce phosphatidylinosatol
- phosphatidylglycerol to produce cardiolipin (inner mitochondrial membrane)
Synthesis of plasmalogen (ether glycerolipid)
Where does this synthesis take place?
- Fatty Acyl-CoA reacts with DHAP
- The ester in this product is there replaced with a fatty alcohol
- The keto group on carbon 2 is reduced to an alcohol
- Carbon 2 is then esterfied to a fatty acid, and carbon 3 is dephosphorylated, replaced with an alcohol group
- CDP-ethanolamine is added
- The alkyl group is oxidized into an alkenyl group, producing ethanolamine plasmalogen
Takes place in peroxisomes
Which disease is characterized by the inablility to produce plasmalogen? What is the possible outcome of this disease? What is ethanolamine plasmalogen used to produce?
Zellweger disease
can lead to death at an early age
ethanolamine plasmogen is used to produce myelin– impacts brian and CNS
Phospholipases degrade glycerophospholipids.
What is the specific role of phospholipase A1, A2, C, and D?
Where are phospholipases found?
- A1
- removes fatty acyl group on carbon 1 of glycerol moiety
- A2
- removes fatty acid on carbon 2
- usually unsaturated (arachidonic acid)– removed in response to signals for synthesis of eicosanoids
- C
- cleaves the bond joining the glycerol moiety to the phosphate
- D
- cleaves the bond between the phosphate and the and the phosphate
Found in cell membranes or lysosomes
Which molecule must principally be formed in the production of sphingolipids?
Describe this synthesis.
Ceramide
- serine and palmitoyl CoA condense to form a product that is then reduced
- a long chain fatty acid (usually 22 carbons) is added and forms an amide with the amino group
- a double bond is generated, and ceramide is formed
