Chp 21 Flashcards
What are the main classes of lipid biosynthesis?
Fatty Acid Biosynthesis, Phospholipid Biosynthesis, Eicosanoid Biosynthesis, Ether Lipid Biosynthesis, Sphingolipid Biosynthesis, Cholesterol Biosynthesis.
What is the main substrate for fatty acid biosynthesis?
Malonyl-ACP (a 3-carbon source).
What enzyme catalyzes the steps in fatty acid biosynthesis?
Fatty acid synthase.
How is chain elongation terminated in fatty acid biosynthesis?
Once the acyl group reaches 16-18 carbons, thioesterase hydrolyzes the acyl-ACP thioester, releasing palmitate (C16).
What is the starting compound for phospholipid biosynthesis?
Glycerol 3-phosphate, which is converted to phosphatidate.
What enzyme initiates the biosynthesis of prostacyclins, prostaglandins, and thromboxanes?
Prostaglandin H synthase (COX).
What is the starting molecule for ether lipid biosynthesis?
Dihydroxyacetone phosphate (DHAP).
What is the backbone used in sphingolipid biosynthesis?
Serine.
What is the precursor for cholesterol biosynthesis?
Acetyl-CoA.
What are the three stages of fatty acid biosynthesis?
Initiation, Chain Elongation, Termination.
What is the role of acetyl-CoA carboxylase in fatty acid biosynthesis?
It catalyzes the carboxylation of acetyl-CoA to form malonyl-CoA.
What enzyme converts malonyl-CoA to malonyl-ACP?
Malonyl CoA:ACPtransacylase.
What enzyme catalyzes the condensation of malonyl-ACP and acetyl-CoA/ACP?
3-Ketoacyl ACP synthase (KAS).
What coenzyme is used in the reduction reactions during elongation?
NADPH.
What happens when the acyl group reaches 16-18 carbons?
Thioesterase hydrolyzes the acyl-ACP thioester, releasing palmitate (C16).
What are the three main modifications fatty acids undergo after release from ACP?
Elongation (by elongases), Desaturation (by desaturases), Activation (by Acyl-CoA synthetase).
How are double bonds introduced into fatty acids?
By desaturases, using O₂ as an oxidant and regenerating the enzyme via NADH oxidation.
