BCH 4024 Exam 3 Content Chapter 23 (Ketones and Fatty Acid Synthesis)

ketone bodies

small, transportable forms of acetate that are great at delivering acetate or acetyl-CoA in times of energy or glucose deficiency

where does ketogenesis occur?

mitochondria of liver cells

-what is Step 1 of ketogenesis?

-what enzyme is involved in this step?

-two molecules of acetyl-CoA join to form acetoacetyl-CoA by releasing CoA-SH

-thiolase

-what is Step 2 of ketogenesis?

-what enzyme is involved in this step?

-acetoacetyl-CoA combined with H₂O and another molecule of acetyl-CoA to form CoA-SH and

-HMG-CoA synthase

-what is Step 3 of ketogenesis?

-what enzyme is involved in this step?

-HMG-CoA is broken down to acetoacetate and acetyl-CoA

-HMG-CoA lyase

what is acetoacetate produced from ketogenesis converted to?

-acetone or D-ß-hydroxybutryrate

what is the mechanism by which acetone is produced from acetoacetate?

acetoacetate uses acetoacetate decarboxylase to release CO₂ and produce acetone

what is the mechanism by which D-ß-hydroxybutyrate is produced from acetoacetate?

acetoacetate uses D-ß-hydroxybutyrate dehydrogenase to oxidize NADH into NAD⁺ and produce D-ß-hydroxybutyrate

what is the fate of acetate produced by ketogenesis in the liver?

exhaled through the breath

what is the fate of acetoacetate and D-ß-hydroxybutyrate produced by ketogenesis in the liver?

it is exported to hepatic tissue from the liver mitochondria to prepare for the citric acid cycle

how is D-ß-hydroxybutyrate converted back to acetyl-CoA in extrahepatic tissue?

-D-ß-hydroxybutyrate is converted to acetoacetate

-acetoacetate is converted to acetoacetyl-CoA by using ß-ketoacyl-CoA transferase to convert succinyl-CoA to succinate

-acetoacetyl-CoA is converted to 2 molecules of acetyl-CoA by using thiolase to add CoA-SH to the molecule

what must acetyl-CoA be converted to for fatty acid synthesis?

malonyl-CoA

how does acetyl-CoA produce malonyl-CoA?

acetyl-CoA carboxylase (ACC) uses HCO₃⁻ and ATP to produce ADP, Pi, and malonyl-CoA

acetyl-CoA carboxylase is __________(regulated, unregulated), and __________(does, does not) require biotin?

regulated; does

how is the fatty acid synthase complex activated?

acetyl-CoA binds to the thiol group of the synthase (KS) end of the complex, while malonyl-CoA binds to the thiol group of the ACP transferase end, forming an acetyl and malonyl group

-what is Step 1 of fatty acid synthesis?

-what enzyme is involved in this step?

-the acetyl and malonyl group undergo condensation, resulting in the loss of CO₂ and production of ß-ketobutyryl-ACP

-ß-ketoacyl-ACP synthase (KS) of fatty acid synthase complex

-what is Step 2 of fatty acid synthesis?

-what enzyme is involved in this step?

-the ketobutyryl-ACP is reduced to hydroxybutyryl-ACP through the oxidation of NADPH to NADP⁺

-ß-ketoacyl-ACP reductase (KR) of the fatty acid synthase complex

-what is Step 3 of fatty acid synthesis?

-what enzyme is involved in this step?

-hydroxybutyryl-ACP is dehydrated to trans-∆²-butenoyl-ACP by releasing water

-ß-hydroxyacyl-ACP dehydratase (DH) of the fatty acid synthase complex

-what is Step 4 of fatty acid synthesis?

-what enzyme is involved in this step?

-trans-∆²-butenoyl-ACP is reduced to butyryl-ACP through the reduction of NADPH to NADP⁺

-enoyl-ACP reductase (ER) of the fatty acid synthase complex

-what is Step 5 of fatty acid synthesis?

-the fatty acid chain is translocated from the ACP to the synthase (KS), freeing up ACP to pick up more malonyl-CoA

where does fatty acid synthesis occur?

cytosol

of the following, __________ (glycolysis, gluconeogenesis, lipolysis, lipogenesis) occur in cell cytosols, while __________ (glycolysis, gluconeogenesis, lipolysis, lipogenesis) occur in cell mitochondria

glycolysis, lipogenesis; gluconeogenesis, lipolysis

how is acetyl-CoA transported to the cytosol for fatty acid synthesis?

it is converted to citrate using oxaloacetate catalyzed by citrate synthase, then goes through the citrate transporter and is converted back to acetyl-CoA using citrate lyase

which enzyme converts malate to pyruvate to be transported to the mitochondria and produce oxaloacetate?

the malic enzyme

which enzyme catalyzes the conversion of a 16-carbon fatty acid to an 18-carbon fatty acid?

elongase

which enzyme catalyzes the creation of a cis unsaturated fatty acid from a saturated fatty acid?

desaturase

what is the allosteric activator of fatty acid synthesis?

citrate

what are the allosteric inhibitors of fatty acid synthesis?

glucagon, epinephrine, high AMP, and palmitoyl-CoA