Lipids 3 COPY Flashcards
Where do we get fatty acids?
Diet Synthesis from excess carbohydrates, fat and protein components (acetyl co a)
Where does fatty acid synthesis occur?
Liver, lactating mammary gland, adipose tissue
What is fatty acid synthesised from ?
Acetyl co a
What chemicals are needed for FA synthesis?
NADPH and ATP and acetyl co a
Where does fatty acid synthesis take place?
Cytosol
Where is acetly co a formed?
In the mitochondria
How does the acetyl co a pass over the mitochondrial membrane into the cytosol?
Via the citrate shuttle, occurs when citrate concentration in the mitochondria is high. Citrate molecule passes over the mitochondrial matrix
Oxaloacetate plus citrate synthase plus acetyl co a =
Citrate
Citrate plus citrate lyase =
Acetyl co a plus oxaloacetate
Oxaloacetate plus NAD plus malate dehydrogenase=
Malate
Malate plus malate enzyme =
Pyruvate + NADPH
Pyruvate (crosses membrane) plus pyruvate carboxylase =
Oxaloacetate
What enzymes are involved in the synthesis of fatty acids?
Acetyl co a carboxylase (activation / regulation)Fatty acid synthase (multifunctional enzyme)
What is the product of fatty acid synthesis?
Palmitic acid
What enzyme is needed for the formation of malonyl co a ?
Acetyl CoA Carboxylase, committed step in fatty acid synthesis, c-c bond requires much energy supplied indirectly by synthesising malonyl co a
What is the regulatory enzyme?
ACC - Acetyl CoA Carboxylase
How is ACC activated?
By citrate, indicates that Glucose levels are high so makes FA
What de-activates ACC?
Palmitoyl CoA (when enough fatty acid is made)
Insulin?
High levels of plasma insulin cause the dephosphorylation of acetly co a phosphorylase thus promoting the formation of malonyl-CoA from acetyl-CoA, and consequently the conversion of carbohydrates into fatty acids
Glucagon and epinephrine?
Deactivates, glucagon (made in the pancreas) causes the liver to break down glycogen to glucose, therefore is present during low levels of glucose, so no fatty acid synthesis is taking place at this time. Epinephrine is adrenaline - released into the blood during starvation and exercise cause the phosphorylation of acetyl CoA phosphorylase, inhibiting lipogenesis in favour of fatty acid oxidation via beta-oxidation.
What is the overall reaction for palmitate?
8 acetyl CoA + 14 NADPH + 14H+ +7ATP -> Palmitate (C16) + 8CoA + 14 NADP+ 7ADP +7Pi + 7H2O
During elongation which enzyme is responsible for producing Aceto-Acetyl ACP?
Acyl Malonyl ACP
What are the three main reactions involved with fatty acid synthesis (opposite to degradation)?
Reduction, dehydration reduction
What is used instead of NADH and FADH2?
NADPH
