Fatty Acids - created from Mind Map

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Fatty Acid Biosynthesis

Occurs in the cytoplasm

Occurs in the liver, kidney, brain, lungs, mammary and adipose tissue

Acetyl coA myst first be converted into malonyl CoA by acetyl CoA carboxylase.

Remaining reactions take place on a multifunctional protein called fatty acid synthetase (FAS)

Formation of malonyl CoA involves covalent binding of CO2 to biotin using ATP hydrolysis.

Using the same enzyme, CO2 is then tranferred to acetyl CoA, producing malonyl-CoA

Initial condensation involves an acetyl group and a malonyl group.

Acetyl group and malonyl group must be transferred from their CoA derivatives to a condensing enzyme and ACP.

Four reactions - condensation, reduction, dehydration and then another reduction.

Lipolysis

TAG is formed from acyl CoA and glycerol-3-phosphate in the adipose tissue.

Glucose entry into the adipocytes is facilitated by GLU4 transporter

When glucose levels are high, a large proportion is converted to acetyl CoA and then to LCFA or goes into the TCA cycle.

Insulin also activates lipoprotein lipase (LPL) resulting in the hydrolysis of TAG contained in the chylomicrons.

Regulation

As glucose runs out, it is directed to the formation of glycerol 3-phosphate and TAG.

Provides FA for esterfication with G-3-P inside adipose tissue.

Adrenalin act rapidly in promoting lipolysis by stimulating membrane bound adenyl cyclase, thus increasing levels of cAMP

Increasing levels of cAMP are responsible for converting inactive HSL into its active phosphorylated form thus promoting lipolysis

Glucocorticoids promote lipolysis through a cAMP-independent pathway.

Intracellular cAMP levels are reduced through the activity of cAMP dependent phosphodiesterase which is activated by insulin.

They promote gene transcription and so increase HSL biosynthesis.

Acetyl CoA carboxylase is allosterically activated by citrate and isocitrate and inhibited by palmitoyl CoA negative feedback.

Insulin stimulates acetyl CoA carboxylase activity.

Glucagon and adrenalin inhibit it by increasing intracellular levels of cAMP.

Catalysed by acetyl transacetylase (ATP) and malonyl transacetylase (MT)

GLUT 4 - Translocated from the Golgi complex to the plasma membrane in the presence of insulin.

cAMP stimulates cAMP-dependent protein kinase (PKa)

Fatty Acids

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