Biochemistry - Fatty Acid Synthesis Flashcards
Which molecule can leak out of the mitochondria into the cytoplasm, inhibiting glycolysis and activating FA synthesis?
Citrate.
Which molecule is the building block for FA synthesis? What enzyme makes this molecule from citrate? What are the byproducts of this reaction?
Citrate lyase makes acetyl coA and oxaloacetate from citrate.
Where does the NADPH come from that is used for FA synthesis?
PP shunt and from malic enzyme reaction (malate to pyruvate)
What is ChREBP?
It is a transcription factor involved in acetyl coA carboxylase and fatty acid synthase transcription.
How is ChREBP regulated?
When unphosphorylated, it can enter the nucleus to increase ACC and FAS transcription. Glucagon and epinephrine phosphorylate it to block FA synthesis. Insulin and glucose catabolism molecules (G6P, X5P) promote unphosphorylated form.
What is the major regulated step in FA synthesis?
acetyl coA to malonyl coA with acetyl coA carboxylase.
Does acetyl coA carboxylase require a cofactor?
Yes, Biotin!
Is the phosphorylated form of acetyl coA carboxylase active or inactive?
It is in the inactive monomer form.
What molecules regulate acetyl coA carboxylase?
Palmitoyl coA, malonyl coA, glucagon, epinephrine phosphorylate ACC to inactivate.
Citrate, insulin dephosphorylate ACC to promote polymerization and activation.
What is the energy efficiency of carbohydrate conversion to fatty acids?
81%
What is NASH?
Non-alcoholic steatohepatitis. Fatty liver + inflammation. Major cause of transplants in the U.S.
What enzyme in ketone body metabolism is present in the brain but not in the liver? Why?
3-keto-acyl coA transferase is not in the liver to prevent futile cycling.
How does ketoacidosis occur in type 1 (insulin dependent) diabetics?
The body doesn’t know that it has glucose, so the liver thinks it needs to make ketone bodies for the brain. The brain has glucose, though, and prefers to use glucose over ketone bodies. Ketone bodies build up and are put into the urine, pulling Na+ and K+ counterions. Loss of these ions reduces blood buffering ability and causes acidosis.
What do hydroxylases do to FA’s?
They add -OH to the alpha carbon of some FA’s used in nervous tissues.
What is the smallest omega number where human desaturases can add a double bond?
7 (so really delta-9)
