Scientific Foundations I: Diabetic Ketoacidosis
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Questions and Answers

What is a primary condition associated with patients who have type 1 diabetes?

  • Insulin resistance
  • Diabetic ketoacidosis (correct)
  • Hyperosmolar hyperglycemic state
  • Hypoglycemia

    • Which of the following statements is true about the adipose tissue of patients with hyperosmolar hyperglycemic state (HHS)?

  • It produces no insulin.
  • It releases more fatty acids than those with DKA.
  • It releases much less fatty acids than those with DKA. (correct)
  • It releases fatty acids at a normal rate.

    • Which enzyme is primarily responsible for the oxidation of saturated fatty acids in the first step of β-oxidation?

  • b-hydroxacyl-CoA dehydrogenase
  • Acyl-CoA acetyltransferase
  • Enoyl-CoA hydratase
  • Acyl-CoA dehydrogenase (correct)

    • What is the end product of one cycle of the β-oxidation process?

    <p>Two acetyl-CoA molecules</p> Signup and view all the answers

    Which enzyme involves the addition of water to the double bond during fatty acid oxidation?

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

    What role does NAD+ play in the β-oxidation of fatty acids?

    <p>It is an electron acceptor.</p> Signup and view all the answers

    What is the main difference in insulin production between type 1 and type 2 diabetes as it relates to diabetic ketoacidosis?

    <p>Type 1 produces no insulin, type 2 can produce some.</p> Signup and view all the answers

    What is released during the β-oxidation of fatty acids that enters the mitochondrial respiratory chain?

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

    What role does Acyl-CoA Dehydrogenase play in fatty acid oxidation?

    <p>It binds to the mitochondrial inner membrane and catalyzes the first step of β-oxidation.</p> Signup and view all the answers

    Which enzyme is involved in the oxidation of monounsaturated fatty acids?

    <p>D3,D2-enoyl-CoA isomerase</p> Signup and view all the answers

    What is the yield of ATP from the complete oxidation of palmitoyl-CoA?

    <p>108 ATP molecules</p> Signup and view all the answers

    What is produced at the end of the b-oxidation process of odd-numbered fatty acids?

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

    When does the complete oxidation of odd-number fatty acids primarily occur?

    <p>When derived from the diet</p> Signup and view all the answers

    Which molecules are classified as ketone bodies?

    <p>Acetone, acetoacetate, and D-b-hydroxybutyrate</p> Signup and view all the answers

    Which statement about odd-number fatty acids is true?

    <p>They lead to the production of propionyl-CoA during oxidation.</p> Signup and view all the answers

    What happens when water is added to double bonds during fatty acid oxidation?

    <p>It hydrates and prepares the fatty acid for further oxidation.</p> Signup and view all the answers

    Which ketone bodies are primarily synthesized in the liver mitochondria?

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

    What is the first step in the process of ketogenesis?

    <p>Condensation of two acetyl-CoA</p> Signup and view all the answers

    Which enzyme catalyzes the condensation of acetyl-CoA in ketogenesis?

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

    What role does β-ketoacyl-CoA transferase play in the metabolism of ketone bodies?

    <p>Activates acetoacetate for conversion to acetyl-CoA</p> Signup and view all the answers

    Why can't the liver use ketone bodies as fuel?

    <p>Liver lacks the enzyme β-ketoacyl-CoA transferase</p> Signup and view all the answers

    What is primarily produced as a byproduct of ketone body metabolism?

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

    Which of the following statements about acetoacetate is true?

    <p>It is involved in the activation process of ketone bodies.</p> Signup and view all the answers

    What is the final product of the conversion of ketone bodies into metabolic fuel?

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

    Where does fatty acid synthesis primarily take place?

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

    What is the result of the condensation of the activated acyl chain with the malonyl group?

    <p>Decarboxylation and chain extension by two carbon units</p> Signup and view all the answers

    What is the starting material for fatty acid synthesis?

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

    Which enzyme is identified as the committed first step in fatty acid synthesis?

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

    Which reducing agent is used for reducing the b-keto product during fatty acid synthesis?

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

    What happens to the newly extended acyl chain after its formation?

    <p>It is translocated to the cysteine residue</p> Signup and view all the answers

    What inhibits the enzyme CAT I in fatty acid synthesis?

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

    What initiates the cycle of fatty acid synthesis after the acyl chain extension?

    <p>Transfer of another malonyl group to the ACP domain</p> Signup and view all the answers

    Which group is attached to the Acyl Carrier Protein during fatty acid synthesis?

    <p>4’-phosphopantetheine</p> Signup and view all the answers

    Which step in the fatty acid synthesis process closely resembles b-oxidation?

    <p>Reduction of the b-keto product</p> Signup and view all the answers

    What is primarily responsible for the hormonal regulation of fatty acid synthesis in the liver?

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

    What crucial problem occurs regarding the transport of Acetyl-CoA?

    <p>It cannot be transported across the mitochondrial inner membrane.</p> Signup and view all the answers

    What occurs after Acetyl-CoA is converted in fatty acid synthesis?

    <p>It forms malonyl-CoA through carboxylation.</p> Signup and view all the answers

    Study Notes

    Diabetic Ketoacidosis (DKA)

    • DKA is a severe complication of diabetes, particularly prevalent in type 1 diabetes due to complete insulin deficiency.
    • In type 2 diabetes, DKA can occur but may present as hyperosmolar hyperglycemic state (HHS), which does not involve ketoacidosis.
    • Adipose tissue in HHS releases significantly fewer fatty acids compared to DKA conditions.

    Oxidation of Fatty Acids

    • β-Oxidation Process:
      • Involves phases where Acyl-CoA dehydrogenase transfers electrons to the mitochondrial respiratory chain.
      • Includes hydration by enoyl-CoA hydratase and further oxidation by β-hydroxacyl-CoA dehydrogenase using NAD+.
      • Acyl-CoA acetyltransferase cleaves off 2 carbon units, producing acetyl-CoA from saturated fatty acids.
    • Palmitate (16 carbon units) yields 108 ATP molecules when oxidized to CO2 and H2O.
    • Three isozymes of acyl-CoA dehydrogenase exist for varying chain lengths of fatty acids.
    • Mono-unsaturated fatty acid oxidation involves D3,D2-enoyl-CoA isomerase.
    • Odd-numbered fatty acids are dietary sources not stored in human cells and produce propionyl-CoA, further oxidized for energy.

    Ketone Bodies

    • Comprise acetone, acetoacetate, and D-β-hydroxybutyrate; synthesized mainly in liver mitochondria.
    • Acetone acts as a minor byproduct and is typically exhaled.
    • Ketogenesis starts with the condensation of acetyl-CoA catalyzed by thiolase, leading to acetoacetate formation.
    • Ketone bodies are converted back into acetyl-CoA with β-ketoacyl-CoA transferase unavailable in the liver, preventing liver utilization as fuel.

    Fatty Acid Synthesis

    • Synthesis occurs in the cytoplasm, using acetyl-CoA, which is transported from mitochondria as it cannot cross the mitochondrial membrane directly.
    • Acetyl-CoA carboxylase catalyzes the committed step of fatty acid synthesis and is a primary target for hormonal regulation, producing malonyl-CoA.
    • Fatty Acid Synthase (FAS) operates as a single polypeptide housing multiple enzymatic activities necessary for sequential fatty acid elongation.
    • The process involves thioester linkages, attachment to acyl carrier protein (ACP), and a cyclical condensation and reduction process utilizing NADPH.

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    Description

    This quiz explores the metabolism of fat and ketone bodies, focusing on diabetic ketoacidosis (DKA) in patients with diabetes. Understand the biochemical processes involved and the implications of DKA in type 1 diabetes management.

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