Lipids 3 Flashcards
What are fatty acids synthesised from?
Acetyl CoA - a derivative of carbohydrate and protein. using ATP and NADPH.
Where is acetyl CoA and Fatty acid synthesised?
Acetyl Coa synthsised in the mitochondria and the Fatty Acid in the cytosol.
How is Acetyl CoA transported form the mitochondria to the cytosol for fatty acid synthesis?
The citrate shuttle
What compounds move in and out of the mitochondria during the citrate shuttle?
Citrate moves out carrying acetyl CoA
Pyruvate moves back in
What are the 2 reactions of the citrate shuttle within the mitochondria and their enzymes?
Pyruvate -> oxaloacetate (pyruvate carboxylase)
Oxaloacetate + Acetyl CoA -> Citrate (Citrate synthase)
What are the 3 main reactions of the citrate shuttle in the cytosol and their enzymes>?
Citrate -> oxaloacetate + Acetyle-CoA (Citrate Lyase)
Oxaloacetate + NADH -> Malate (Malate dehydrogenase)
Malate -> Pyruvate + NADPH (malate enzyme)
When does the citrate shuttle occur?
When citrate concentration in the mitochondria is high.
What is the first committed step of Fatty acid synthesis?
Acetyl CoA + HCO3 + ATP -> Malonyl-CoA +ADP + Pi + H+ (Acetyl-CoA carboxylase)
What Stimulates Acetyl-Coa Carboxylase?
Citrate signals thers enough glucose so Acetyl-CoA should be stored as FA.
Insulin
What deactivates Acetyl-CoA carboxylase?
Palmitoyl CoA signals theres enouh FA so halt synthesis
Glucagon
Epinephrine
What two groups are condensed in the first stage of FA synthesis?
Activated Acyl Group and Activated Malonyl group.
What are the 4 reactions from acyl and malonyl groups to an acyl group 2 carbons longer? (one cycle of FA synthesis)
Condensation
Reduction
Dehydration
Reduction
what is the overall equation for the first cycle of FA synthesis?
2 Acetyl CoA + 2 NADPH + 2 H+ + 1 ATP -> Acyl group (2 carbons longer) + 2 NADP + ADP + Pi + H2O.
(Every cycle after the first only used one acetyl CoA to make malonyl-CoA and the extended Acyl group from the last cycle)
What carrier protein is used in FA synthesis?
ACP (Acyl Carrier Protein)
What happens when a synthesised FA reaches its desired length?
The FA (Palmityl-CoA) is cleaved from the carrier protein ACP by a thioesterase.
What enzyme is used in most of FA synthesis?
Multifunctional Fatty Acid Synthase
What electron acceptor is used in FA synthesis?
NADP+ (NADPH)
How much NADPH is needed for FA synthesis and where does it come from?
14 NADPH molecules are needed to produce a molecule of Palmityl-CoA.
8 come from the malate -> Pyruvate reaction in the citrate shuttle
6 comes from the Pentose Phosphate Pathway (PPP)
What FA is produced in basic FA synthesis?
Palmityl-CoA (16C)
Where does further modification of teh Palmityl-CoA occur?
Mitochondria and ER
What is FA used for if not energy?
Storage as adipose tissue?
How does FA become Adipose tissue?
FATTY ACID + glycerol -> TAG + protein + phospholipid + cholesterol -> VLDL -> ADIPOSE TISSUE.
Where do FA synthesis and Degradation occure?
Synthesis occurs in the cytosol and degradation in the mitochondrial matrix
What carier protein is involved in synthesis and which in deggradation?
ACP (Acyl carrier protein) is used in synthesis while CoA is used in Degradation
