Exam 3 Review Zaidi Flashcards
Where does fatty acid synthesis take place?
Primarily in the liver, but also occurs in adipose tissue, brain, kidneys and lactating mammary glands
What does fatty acid synthesis require?
Coordination between cytosolic and mitochondrial reactions
What is the end product of fatty acid synthesis?
Palmitic acid
What is the precursor of fatty acid synthesis?
Acetyl CoA
What is the first phase of fatty acid synthesis?
Cytosolic entry of acetyl CoA
What is the second phase of fatty acid synthesis?
Generation of Malonyl CoA (rate limiting reaction)
What is the third phase of fatty acid synthesis?
Fatty acid chain formation (enzyme fatty acid synthase catalyzes 7 reactions that incorporate acetyl CoA, Malonyl CoA into palmitate (a C16 fatty acid))
What is the shuttle system that moves reactants into the cytosol?
Citrate Shuttle which moves citrate to the cytosol where it is formed to oxalocetate by ATP citrate lyase where acetyl CoA is a byproduct
What is used as a co-factor in the conversion of acetyl CoA to Malonyl CoA?
Biotin
What is the function of Malonyl CoA?
Regulator that inhibits carnitine acyltransferase
Prevents fatty acid synthesis and degradation from occurring simultaneously
Where does fatty acid synthesis take place?
Fatty Acid Synthase complex
What is fatty acid synthase composed of?
2 identical dimers, 7 enzyme activities and an acyl carrier protein
What is the formula for fatty acid synthesis?
1 Acetyl CoA+7 Malonyl CoA+14 NADPH+14 H+
What is the order of cycles of fatty acid synthase?
Condensation, reduction, dehydration, reduction performed 7 times before product release
What are the points of regulation for fatty acid synthesis?
ATP citrate lyase Phase 1
Acetyl CoA carboxylase Phase 2 (rate limiting step)
Fatty acid synthase Phase 3
How is ATP citrate lyase regulated?
Stimulated by phosphorylation
Expression induced by glucose/insulin
Induction of gene expression counteracted by PUFAs and leptin
How is acetyl CoA carboxylase regulated?
Allosterics
Phosphorylation and dephosphorylation
Induction
How is FAS regulated?
Allosterics- presence of phosphorylated sugars increase activity
Induction and repression at genetic level
How is fatty acids elongated?
Occurs in mitochondria or SER Lengthened 2 carbons at a time NADPH used as reducing power SER uses malonyl CoA as carbon donor Mito uses acetyl CoA as carbon donor
What is desaturation?
Introduction of double bonds in fatty acids
Where does desaturation occur?
SER using NADPH or NADH and oxygen catalyzed by acyl CoA desaturases
How many desaturases do humans have and where do they induce double bonds
4
Between carbons 4-5, 5-6, 6-7, 9-10
Can fatty acids with double bonds beyond C9 and 10 be synthesized in humans?
No, must be consumed in diet, known as essential fatty acids ie Omega 3 and Omega 6
What is the precursor that must be ingested to form arachidonic acid?
Linoleic acid, used to make eicosanoids
