6. Reactions, IC localization and energy balance of the biosynthesis of simple and complex lipids, and ketone bodies

common pathway for biosynthesis of simple and complex lipids?

in order to synthesize lipids, both complex and simple, we need two common substrates: glycerol-3-P and fatty-acyl-CoA

for synthesis of complex lipid we need an additional head-group

synthesis of lipids occur in adipose tissue and liver, on the surface of the smooth ER and the inner mitochondrial membrane

Sources of glycerol 3-P?

the main way to obtain glycerol-3-P is through the glycolytic intermediate dihydroxyacetone phosphate

DHAP is then converted to glycerol-3-P by the cytosolic, NAD+-linked glycerol-3-P dehydrogenase

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another way is by phosphorylation of glycerol, by glycerol kinase

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last way: glycerogenesis

formation of phosphatidic acid?

acyl transferase will catalyze the acylation of the two free hydroxyl groups of the glycerol-3-P forming diacylglycerol-3-P, aka phosphatidic acid

formation of TAG?

phosphatidic acid → phosphate group is removed by hydrolyzing of phosphatidic phosphatese

now the 1,2-DAG is acylated by acyl-transferase, finishing of TAG

formation of complex lipids?

the polar head of the complex lipids are attached through a phosphodiester bond at C3

CDP, a nucleotide is essential in the formation of complex lipids

either the polar head group, or the phosphatidic acid is activated by cytidine diphosphate

synthesis of phosphatidylserine and phosphatidylethanolsamide?

synthesis of phosphatidylcholine

synthesis of cardiolipin

synthesis of phosphatidyl inositol?

Ketone body synthesis?

acetyl-CoA derived from the oxidation of fatty acid can be synthetized in ketone bodies in the liver

the ketone bodies are acetone, acetoacetate and β-hydroxybutyrate

the entire process takes place in the mitochondrial matrix

ketone body synthesis, reactions and enzymes?

thiolase

HMA-CoA synthase

HMA-CoA lyase

acetoacetate carboxylase / β-hydroxybutyrate DH

how can we utilize ketone bodies?

why can’t the liver utilize ketone bodies?

because the liver lacks the β-ketoacyl-CoA transferase enzyme, so it can’t break down ketone bodies