Flashcards in Fatty Acid and TAG Synthesis Deck (35):
Needed in diet
Linoleic acid 18:2(9,12)
Linolenic acid 18:3(9,12,15)
If Linoeic isn't around arachadonic is essential
Major sites of Fatty acid synth
Liver, lactating mammary gland
Minor sites of Fatty acid synth
Coenzymes needed for FA Synth?
Acetyl CoA (pantothenic acid) ATP NADPH CO2
Where in the cell does FA synth take place?
How does acetyl CoA get to the cytoplasm
When does FA synth take place?
When ATP is high and inhibits isocitrate dehydrogenase
How is citrate made from acetyl CoA?
Addition to oxaloacetate by citrate synthase
What enzyme catalyzes the rate limiting step of FA synth?
Acetyl CoA carboxylase (requires biotin) and 1 ATP per malonyl CoA formed
How is the active ACC different from the inactive?
Active is polymer
Inactive is dimer
Name one positive and one negative allosteric modifier of ACC.
+=citrate (substrate activation)
-=palmitoyl CoA (product inhibition)
How is ACC regulated hormonally?
Inactivated by phosphorylation (by glucagon, epinephrine, norepinephrine)
What effect does a high fat diet have on ACC? (Same as fasting and glucagon)
Down regulation, decreased synthesis of FA
What effect does a high carb fat free diet have on ACC?
Up regulated, more FA made
Acetyl CoA added to cysteine of condensing arm of FA synthase
Malonyl CoA added to ACP sulfhydryl group
(Takes 2 to tango; second substrate Added to A
Acetyl condensing group adds to malonyl acyl Carrier
Keto group is reduced (adds a hydroxyl group)
Dehydrated to make trans monounsaturated fatty acyl group
NADPH is used to reduce the double bond, leaving a saturated fatty acyl group to be transferred to the condensing enzyme SH
Mnemonic for FA synthase steps
Aaron Makes Terrible Remembering Devices...Not!
What enzyme releases palmitoyl-ACP from the FA synthase?
Where does FA chain elongation occur?
What double bonds can be formed by the three human fatty acid desaturases?
What 3 things does the fatty acid desaturase system need?
NADPH-cytochrome b5 reductase
TAG synthesis step one makes....
Lysophosphatidic acid (glycerol phosphate with 1 FA added)
Step 2 of TAG synthesis makes....
Phosphatidic acid (glycerol phosphate plus two FAs)
Step 3 of TAG synthesis makes....
DAG (by removing the phosphate to make room for a third FA to be added next)
Step 4 of TAG synthesis makes...
What enzyme catalyzes each step of TAG synthesis?
1, 2, & 4 = acylytransferase
Where are chylomicrons made?
What is the cellular location of citrate lyase? What irreversible reaction does it catalyze?
Citrate + ATP ➡️ oxaloacetate+ Ac-CoA + ADP + Pi
What is the cellular location and reaction catalyzes by the malic enzyme?
Malate + NADP ➡️ Pyruvate + CO2 + NADPH