Fatty acid and Triacylglycerol synthesis Flashcards
What is required to produced phospholipids and TAGS
Production of FA, glycerol and phosphate (for PL)
Where do we get the building blocks for production of PL and TAGs
Diet, glucose is main source of C,H and O
What is glycolysis
Sequential breakdown (10 steps) of glucose to produce energy, including addition of phosphate in steps 1-4
How is the glycerol component produced
Enzyme glycerol 3-phosphate dehydrogenase catalyses reaction for dihydroxyacetone phosphate to glycerol 3-phosphate
How do we make a fatty acid
Production of pyruvate in glycolysis (3C), pyruvate moves into the mitochondria and is converted to acetyl CoA (2C) by pyruvate dehydrogenase (PDH)
Acetyl CoA of the basic building block of FA synthesis but cannot leave mitochondria so citrate formed inTCA/krebs cycle using acetyl CoA used as form to exit mitochondria, acetyl CoA regenerated outside mitochondria
Acetyl CoA carboxylase (ACC) catalyses production Malonyl CoA from ACoA (requires ATP)
Fatty acid synthase adds 2 C from MCoA to growing FA chain (starting with 2C from excess acetyl CoA) until complete (up to 16 carbons)
What is the final fatty acid product in humans (C16:0)/ the only fatty acid we can make from scratch
Palmitate
Why must acetyl CoA be converted to citrate to leave the mitochondria
Too large to leave and fatty acid synthesis occurs in the cytoplasm
What is the TCA cycle
Tricarboxylic acid cycle (Krebs cycle) which is a pathway for complete oxidation of the carbon derived in glycolysis with an output of NAHD and FADH required for oxidative phosphorylation
What promotes the activity of Acetyl CoA carboxylase
Citrate and insulin
What supresses the activity of Acetyl CoA carboxylase
Glucagon and long chain FA
What is the function of pyruvate dehydrogenase (PDH) in fatty acid synthesis
Conversion of pyruvate to acetyl CoA in mitochondria
What is the function of acetyl CoA carboxylase in fatty acid synthesis
Conversion of acetyl CoA (2C) to Malonyl CoA (3C) in the cytoplasm
What is the function of fatty acid synthase
Addition of 2 carbons from malonyl CoA sequentially to a growing fatty acid chain
What is malonyl CoA
3 carbon substrate for fatty acid synthesis
What happens if further elongation of the fatty acid chain is required beyond 16 C
Further elongation is performed on the smooth endoplasmic reticulum via a series of enzymes that add 2C from malonyl CoA as before depending on cell type (>/=22C)
What is desaturation
Desaturases perform desaturation on only cis conformation FA up to C10 on the SER
What are eicosanoid hormones
LCFA (C20:4) that are derived from linoleate and are a major precursor for signalling molecules e.g. arachidonate which is used to produce prostaglandin
How does aspirin work
Blocks the conversion of arachiodonate (eicosanoid hormone) into prostaglandin (PGH2)
What is the rate controlling step for FA synthesis
Acetyl CoA carboxylase
Where can all the components to make a TAG come from
Glycolysis
What is the function of dihydroxyacetone phosphate in lipid synthesis
Converted to glycerol 3-phosphate in glycolysis to produce glycerol and phosphate complement for phospholipid synthesis
How are TAGs and PLs generated
By stepwise addition of FA/head groups to glycerol phosphate
Describe the pathway TAG and PL synthesis
Activation of fatty acid produced by addition on CoA (Acyl-CoA/LCFA CoA)
Addition of 2 Acyl (LCFA) from acyl CoA to glycerol 3-phosphate (from glycolysis) via glycerol phosphate acyltransferase to produce phosphatidate
Phosphatidate is precursor for TAG (using triacylglycerol synthase complex enzymes to replace phosphate with another FA) and PL synthesis (by addition of head groups)
What is phosphatidate
Precursor that provides substrate for TAG and PL
