biochem 009 fatty acid synthesis part 1(acetyl coa malonyl coa linoleic acid insulin epinephrine
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_____ ____ is the precursor for virtually all fatty acids
how is acetyl CoA exported out of the mitochondrion?
acetyl CoA is transported out of the mitochondria in the form of citrate. Citrate is formed in the mitochondrial matrix by condensation of acetyl CoA with oxaloacetate. This reaction begins the citric acid cycle when energy is required. When the energy needs of the cell have been met, citrate is relocated to the cytoplasm by a transport protein, where it is cleaved by ATP-citrate lyase at the expense of a molecule of ATP to form acetyl CoA.
explain what leptin is
leptin is a hormone made by fat cells which regulates the amount of fat stored in the body. It does this by adjusting both the sensation of hunger, and adjusting energy expenditures. Hunger is inhibited (satiety) when the amount of fat stored reaches a certain level.
how many molecules of NADPH are generated for each molecule of acetyl CoA that is transferred from mitochondria to the cytoplasm?
What are the two pathways that are used to generate NADPH to synthesize fatty acids?
1. the transfer of acetyl CoA to the cytoplasm and the subsequent reactions that it undergoes
2. pentose phosphate pathway
How many NADPH molecules are generated in each of the two pathways that are used to synthesize fatty acids?
- 8 molecules of NADPH are formed when eight molecules of acetyl CoA are transferred to the cytoplasm.
- the additional 6 molecules of NADPH required come from the pentose phosphate pathway
after citrate is broken down into oxaloacetate and acetyl CoA, what is the next thing that happens to the oxaloacetate?
oxaloacetate is reduced to malate by NADH. This reaction is catalyzed by a cytoplasmic malate dehydrogenase.
what happens to malate after it is formed in the reaction between malate dehydrogenase and oxaloacetate?
malate is oxidatively decarboxylated by malic enzyme, forming NADPH and pyruvate in the process
what occurs after malate is converted to pyruvate in fatty acid synthesis?
the pyruvate formed in this reaction readily enters mitochondria, where it is carboxylated to oxaloacetate by pyruvate carboxylase.
what is the difference between acyl CoA and acetyl CoA?
Coenzyme A has a thiol group at one end. Acyl CoA is a generalised thioester group. If it is a methyl, ethyl, propyl, butyl, isobutyl, amyl, pentyl (the list goes on) thioester it is an Acyl CoA. But if it is a methyl thioester, it can be specifically referred to as Acetyl CoA.
what is the enzyme system that catalyzes the synthesis of saturated long-chain fatty acids from acetyl coa, malonyl coa, and NADPH?
fatty acid synthase
mammals lack the enzyme to introduce double bonds at carbon atoms beyond the ____ in the fatty acid chain
some molecules (including certain types of fatty acids and amino acids) are called "essential." What does this mean?
the body cannot produce these molecules and they must be supplied by the diet
what is arachidonate? what is its significance?
it is a 20:4 fatty acid that is the major precursor of several classes of signal molecules: postaglandins, postacyclins, thromboxanes, and leukotrienes.
what are eicosanoids?
signaling molecules that are 20 carbons long
which enzyme catalyzes the committed step of fatty acid synthesis?
acetyl CoA carboxylase
in fatty acid synthesis, acetyl CoA is activated by ____ ___ _______ into ______ ______
acetyl CoA carboxylase, malonyl CoA
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