Y1S2 006 I Biochem Glycolysis, Fat Oxidation, and Ketogenesis
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Questions and Answers

What is the result of high rates of fatty acid oxidation in the liver?

  • Increased TCA cycle activity
  • Enhanced protein synthesis
  • Synthesis of Ketone Bodies (correct)
  • Increased glycogen synthesis

    • What is the term that refers to three biosynthetically related products?

  • Metabolic Paths
  • Glycolysis
  • Ketone Bodies (correct)
  • Fat Oxidation

    • What is the role of hormone-sensitive lipase in fatty acid metabolism?

  • It phosphorylates adenylate cyclase
  • It hydrolyzes FA from triacylglycerols and diacylglycerols (correct)
  • It synthesizes Ketone Bodies
  • It activates PKA

    • Where are Ketone Bodies formed?

    <p>Liver Mitochondria</p> Signup and view all the answers

    What is the purpose of Ketone Bodies in the body?

    <p>To provide an alternative source of metabolic energy</p> Signup and view all the answers

    What is the effect of epinephrine binding to its receptor in fatty acid metabolism?

    <p>It increases cAMP, which then activates PKA</p> Signup and view all the answers

    What is the primary fate of the small amount of acetone formed in the body?

    <p>It is exhaled through the lungs</p> Signup and view all the answers

    What is the purpose of oxaloacetate in the liver during carbohydrate starvation?

    <p>It is used for gluconeogenesis</p> Signup and view all the answers

    What is the enzyme responsible for the formation of β-hydroxy-β-methylglutaryl-CoA (HMG-CoA)?

    <p>HMG-CoA synthase</p> Signup and view all the answers

    What is the result of the condensation of two acetyl-CoA molecules?

    <p>Acetoacetyl-CoA</p> Signup and view all the answers

    What is the enzyme responsible for the interconversion of acetoacetate and β-hydroxybutyrate?

    <p>β-Hydroxybutyrate Dehydrogenase</p> Signup and view all the answers

    What is the precursor to ketone bodies in the liver?

    <p>Acetyl-CoA</p> Signup and view all the answers

    What is the product of the spontaneous decarboxylation of acetoacetate?

    <p>Acetone</p> Signup and view all the answers

    Where does the reaction between acetoacetate and succinyl-CoA occur?

    <p>In the mitochondria</p> Signup and view all the answers

    What is the result of the absence of ketoacyl-CoA-transferase in the liver?

    <p>The liver is unable to utilize ketone bodies</p> Signup and view all the answers

    What is the result of a high level of glucagon on the production of β-hydroxybutyrate?

    <p>It increases</p> Signup and view all the answers

    What is the direct regulator of ketogenesis in the liver?

    <p>The release of free fatty acids from adipose tissue</p> Signup and view all the answers

    What happens to acetyl-CoA when the demand for ATP is high?

    <p>It is further oxidized to CO2</p> Signup and view all the answers

    What is the primary source of fuel for the heart and skeletal muscle in the early stages of starvation?

    <p>Ketone bodies</p> Signup and view all the answers

    What is the fate of fats in the liver if there is sufficient glycerol-3-phosphate?

    <p>They are esterified to glycerol in the production of triacylglycerols</p> Signup and view all the answers

    What is the substrate for the biosynthesis of neonatal cerebral lipids?

    <p>Acetoacetate and β-hydroxybutyrate</p> Signup and view all the answers

    What is the effect of insulin on ACC?

    <p>It inhibits ACC</p> Signup and view all the answers

    How do extrahepatic tissues utilize ketone bodies?

    <p>By converting β-hydroxybutyrate to acetoacetate and then to acetoacetyl-CoA</p> Signup and view all the answers

    What is the name of the enzyme that is present in all tissues except the liver?

    <p>Ketoacyl-CoA-transferase</p> Signup and view all the answers

    What is the main cause of diabetic ketoacidosis in untreated insulin-dependent diabetes mellitus?

    <p>Reduced supply of glucose and increased fatty acid oxidation</p> Signup and view all the answers

    What is the effect of acidification of the blood in diabetic ketoacidosis?

    <p>It impairs the ability of hemoglobin to bind oxygen</p> Signup and view all the answers

    What is a warning sign of diabetic ketoacidosis?

    <p>Presence of ketones in urine</p> Signup and view all the answers

    What is the typical progression of diabetic ketoacidosis?

    <p>It develops progressively over time</p> Signup and view all the answers

    What is the primary source of energy for the body during healthy regular life?

    <p>Glucose breakdown</p> Signup and view all the answers

    What is the term that describes the physiological state resulting from a reduced supply of glucose and a concomitant increase in fatty acid oxidation?

    <p>Diabetic ketoacidosis</p> Signup and view all the answers

    Study Notes

    Metabolic Paths

    • Three metabolic paths: Glycolysis, Fat Oxidation, and Ketogenesis

    Glycolysis

    • Epinephrine binds to its receptor, activating adenylate cyclase, leading to phosphorylation of hormone-sensitive lipase
    • This releases fatty acids from triacylglycerols, diacylglycerols, and monoacylglycerols through the action of monoacylglycerol lipase

    Fat Oxidation

    • Epinephrine binds to its receptor, activating adenylate cyclase, leading to phosphorylation of hormone-sensitive lipase
    • This releases fatty acids from triacylglycerols, diacylglycerols, and monoacylglycerols through the action of monoacylglycerol lipase

    Ketogenesis

    • During high rates of fatty acid oxidation, acetyl-CoA is generated in excess of the TCA cycle's capacity
    • This leads to the synthesis of Ketone Bodies (Acetoacetate, β-hydroxybutyrate, and acetone)
    • Ketone Bodies are formed in Liver Mitochondria
    • Acetoacetate and β-hydroxybutyrate are formed from acetyl-CoA in the liver mitochondria

    Formation of Ketone Bodies

    • Ketogenesis begins with the condensation of two acetyl-CoA molecules to form acetoacetyl-CoA
    • Acetoacetyl-CoA and an additional acetyl-CoA are converted to β-hydroxy-β-methylglutaryl-CoA (HMG-CoA) by HMG-CoA synthase
    • HMG-CoA is then cleaved into acetoacetate and acetyl-CoA

    β-Hydroxybutyrate Dehydrogenase

    • Catalyzes interconversion of the ketone bodies acetoacetate and β-hydroxybutyrate
    • The first step involves the reversal of the β-hydroxybutyrate dehydrogenase reaction
    • The second step involves the action on acetoacetate by succinyl-CoA transferase (also called ketoacyl-CoA-transferase)

    Regulation of Ketogenesis

    • Control of free fatty acid release from adipose tissue directly affects the level of ketogenesis in the liver
    • The liver has sufficient supplies of glycerol-3-phosphate, most of the fats will be turned to the production of triacylglycerols
    • Acetyl-CoA can be completely oxidized in the TCA cycle if the demand for ATP is high
    • The level of fat oxidation is regulated hormonally through phosphorylation of ACC, which can activate or inhibit it

    Acetone Formation

    • Acetoacetate can undergo enzymatic conversion to β-hydroxybutyrate through the action of β-hydroxybutyrate dehydrogenase or spontaneous decarboxylation to acetone

    Increased Release of Ketones

    • When the level of glucagon is high, the production of β-hydroxybutyrate increases
    • When carbohydrate utilization is low or deficient, the level of oxaloacetate will also be low, resulting in a reduced flux through the TCA cycle, leading to increased release of ketone bodies from the liver

    Utilization of Ketone Bodies

    • Ketone bodies are utilized by extrahepatic tissues through the conversion of β-hydroxybutyrate to acetoacetate and of acetoacetate to acetoacetyl-CoA
    • Heart and skeletal muscle will consume primarily Ketone Bodies to preserve glucose for use by the brain during early stages of starvation

    Diabetic Ketoacidosis

    • The most significant disruption in the level of ketosis occurs in untreated insulin-dependent diabetes mellitus
    • This leads to diabetic ketoacidosis (DKA), resulting from a reduced supply of glucose and a concomitant increase in fatty acid oxidation
    • The increased production of acetyl-CoA leads to ketone body production that exceeds the ability of peripheral tissues to oxidize them
    • Acidification of the blood occurs due to the increase in ketone bodies, which can impair the ability of hemoglobin to bind oxygen

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    Ketogenesis: metabolic pathways PDF

    Description

    This quiz covers the basics of metabolic pathways, including glycolysis, fat oxidation, and ketogenesis. It also explores the role of epinephrine in activating hormone-sensitive lipase and the breakdown of fatty acids. Test your knowledge of these important biochemical processes!

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