Harper's Biochemistry Chapter 22 - Oxidation of Fatty Acids: Ketogenesis
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Questions and Answers

What is a potential consequence of excessive ketone body production during prolonged diabetes?

  • Diabetic neuropathy
  • Hypoglycemia
  • Ketoacidosis (correct)
  • Fatty liver disease

    • Which substance is critical as a coenzyme in the process of fatty acid oxidation?

  • Coenzyme A
  • ATP
  • Vitamin D
  • NAD+ (correct)

    • What happens to fatty acids before they are catabolized in the body?

  • They are converted into carbohydrates.
  • They are activated. (correct)
  • They are sent to the blood for transport.
  • They are broken down into glucose.

    • What condition can lead to impaired fatty acid oxidation and subsequent hypoglycemia?

    <p>Carnitine deficiency</p> Signup and view all the answers

    How are long-chain fatty acids transported in plasma?

    <p>Bound to albumin</p> Signup and view all the answers

    Which type of fatty acids is more water-soluble?

    <p>Short-chain fatty acids</p> Signup and view all the answers

    Which process is directly dependent on fatty acid oxidation?

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

    What is the primary role of acetoacetate in extrahepatic tissues?

    <p>It is converted back to acetoacetyl-CoA for energy production.</p> Signup and view all the answers

    Which compound directly links O-acyl-CoA to acetoacetate for energy utilization?

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

    In the oxidation of unsaturated fatty acids, which alteration occurs during the β-oxidation cycle?

    <p>Conversion of Δ3-cis double bonds to Δ3-trans double bonds.</p> Signup and view all the answers

    What is the end product of the reversible reaction involving 3-hydroxybutyrate during its utilization?

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

    Which of the following statements correctly describes the production of ketone bodies in the liver?

    <p>Results from an active enzymatic mechanism producing acetoacetate from acetoacetyl-CoA.</p> Signup and view all the answers

    What two carbon units are formed during beta-oxidation?

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

    Which enzyme catalyzes the removal of hydrogen atoms during the first step of beta-oxidation?

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

    What is the role of carnitine in fatty acid oxidation?

    <p>It facilitates the transportation of long-chain fatty acids into the mitochondria.</p> Signup and view all the answers

    How many acetyl-CoA molecules are generated from palmitoyl-CoA (C16) during beta-oxidation?

    <p>8</p> Signup and view all the answers

    What are the reducing equivalents generated during the beta-oxidation pathway?

    <p>NADH and FADH2</p> Signup and view all the answers

    What type of reaction occurs at the beta (3) carbon during the beta-oxidation of fatty acids?

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

    Which statement accurately describes the cleavage process in beta-oxidation?

    <p>It cleaves fatty acids in a cyclic manner.</p> Signup and view all the answers

    What product is directly formed from the oxidation of acyl-CoA in the beta-oxidation pathway?

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

    What is the significance of FADH2 and NADH produced in the beta-oxidation process?

    <p>They are utilized in oxidative phosphorylation for ATP production.</p> Signup and view all the answers

    What is the net gain of ATP per mole of palmitate after considering activation?

    <p>106 mol</p> Signup and view all the answers

    How many moles of FADH2 are produced during the complete oxidation of palmitate?

    <p>7 mol</p> Signup and view all the answers

    What percentage of the free energy of combustion of palmitic acid is represented by the generated ATP?

    <p>33%</p> Signup and view all the answers

    Which component of the ATP generation process is involved in the activation step?

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

    During β-oxidation, how much ATP is produced from NADH per mole of palmitate?

    <p>17.5 mol</p> Signup and view all the answers

    What is the total ATP used during the complete oxidation of palmitate?

    <p>2 mol</p> Signup and view all the answers

    How many moles of Acetyl-CoA are produced from the oxidation of one mole of palmitate?

    <p>8 mol</p> Signup and view all the answers

    What is the total ATP formed through both β-oxidation and the citric acid cycle from palmitate?

    <p>108 mol</p> Signup and view all the answers

    Which of the following steps does NOT contribute to the generation of ATP when oxidizing palmitate?

    <p>Activation step</p> Signup and view all the answers

    What is the total ATP formed per mole of palmitate after accounting for the ATP used in activation?

    <p>106 mol</p> Signup and view all the answers

    Which of the following is a ketone body?

    <p>D-3-Hydroxybutyrate</p> Signup and view all the answers

    What is the role of NAD+ in the reaction involving D-3-Hydroxybutyrate?

    <p>It acts as an oxidizing agent.</p> Signup and view all the answers

    Which compound is an intermediate in the conversion to acetone?

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

    Which of the following statements about ketone bodies is true?

    <p>They are produced primarily during fatty acid oxidation.</p> Signup and view all the answers

    In the context of ketogenesis, what happens to NADH?

    <p>It is oxidized to form NAD+ and release energy.</p> Signup and view all the answers

    Which reaction involves the formation of acetoacetate?

    <p>The oxidation of fatty acids.</p> Signup and view all the answers

    Which of the following ketone bodies is not a direct product of fatty acid oxidation?

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

    Which enzyme is responsible for the conversion of acetoacetate to D-3-Hydroxybutyrate?

    <p>D-3-Hydroxybutyrate dehydrogenase</p> Signup and view all the answers

    What structural feature distinguishes ketone bodies from other metabolic products?

    <p>Presence of a carbonyl group.</p> Signup and view all the answers

    What is a major fate of D-3-Hydroxybutyrate in the body?

    <p>It is converted back to acetyl-CoA for energy production.</p> Signup and view all the answers

    Which of the following statements correctly describes the process of fatty acid breakdown in the mitochondria?

    <p>Fatty acids are degraded to acetyl-CoA and release energy through a separate process.</p> Signup and view all the answers

    During ketogenesis, which of the following conditions favors the synthesis of ketone bodies?

    <p>Low insulin levels and high fatty acid availability.</p> Signup and view all the answers

    Which compound is NOT one of the three primary ketone bodies produced in liver mitochondria?

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

    What is the primary consequence of excessive ketone body production in the body?

    <p>Development of ketoacidosis if prolonged.</p> Signup and view all the answers

    Which stage of fatty acid metabolism is known to be regulated in regard to ketogenesis?

    <p>Conversion of acetyl-CoA to ketone bodies.</p> Signup and view all the answers

    What characterizes the separation of fatty acid oxidation from biosynthesis in the cell?

    <p>Fatty acid oxidation occurs in mitochondria while biosynthesis occurs in the cytosol.</p> Signup and view all the answers

    Impaired fatty acid oxidation can lead to which of the following conditions?

    <p>Hypoglycemia.</p> Signup and view all the answers

    What is the primary product formed from the successive cleavage of fatty acids during β-oxidation?

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

    Which enzyme is responsible for the transfer of acyl groups from CoA to carnitine in the transport of long-chain fatty acids?

    <p>Carnitine palmitoyltransferase-I</p> Signup and view all the answers

    What type of bond is formed during the first step of β-oxidation at the α and β carbon atoms?

    <p>Alkene bond</p> Signup and view all the answers

    During β-oxidation, which of the following compounds is generated as a reducing equivalent?

    <p>FADH2</p> Signup and view all the answers

    What role do FADH2 and NADH play in relation to ATP production during the β-oxidation cycle?

    <p>They are utilized in oxidative phosphorylation to form ATP.</p> Signup and view all the answers

    What is necessary for the fatty acyl-CoA to cross the inner mitochondrial membrane?

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

    In the β-oxidation pathway, how many acetyl-CoA molecules will palmitic acid (C16) yield?

    <p>8</p> Signup and view all the answers

    Which of the following correctly describes the β-oxidation cycle?

    <p>It results in the repetitive cleavage of fatty acids into acetyl-CoA units.</p> Signup and view all the answers

    Which statement about the generation of reducing equivalents during β-oxidation is true?

    <p>Both NADH and FADH2 are generated during the pathway.</p> Signup and view all the answers

    What role does NADPH play in the process described?

    <p>It acts as a reducing agent during ketogenesis.</p> Signup and view all the answers

    Which step in the process of ketogenesis requires the addition of CoA?

    <p>Breakdown of acetoacetyl-CoA by thiolase</p> Signup and view all the answers

    How does the concentration of ketone bodies affect oxidative machinery?

    <p>It leads to saturation of the oxidative machinery.</p> Signup and view all the answers

    What is the possible consequence of extreme ATP yields from NADPH sources in relation to ketone body levels?

    <p>Potential inhibition of ketogenesis</p> Signup and view all the answers

    What is indicated by a rise in blood levels of ketone bodies to 12 mmol/L?

    <p>Saturation of the oxidative machinery</p> Signup and view all the answers

    What is the role of HMG-CoA lyase in ketogenesis?

    <p>It facilitates the splitting of acetoacetyl-CoA into acetoacetate and acetyl-CoA.</p> Signup and view all the answers

    Which of the following is predominantly produced during ketosis?

    <p>D-3-Hydroxybutyrate</p> Signup and view all the answers

    What is required in the mitochondria for ketogenesis to occur?

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

    From which molecule is D-3-Hydroxybutyrate formed?

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

    Which substrate undergoes β-oxidation to contribute to the formation of ketone bodies?

    <p>Fatty acids</p> Signup and view all the answers

    What is the result of the condensation reaction catalyzed by HMG-CoA synthase?

    <p>Formation of HMG-CoA.</p> Signup and view all the answers

    Where in mammals does ketogenesis primarily take place?

    <p>In the liver and rumen epithelium.</p> Signup and view all the answers

    During β-oxidation, what is the fate of a fatty acid before it can contribute to ketone body formation?

    <p>It undergoes dehydrogenation and cleavage to form acetyl-CoA.</p> Signup and view all the answers

    Which of the following is NOT a direct step in the production of ketone bodies?

    <p>Synthesis of cholesterol from acetyl-CoA.</p> Signup and view all the answers

    What is the primary product formed when 3-hydroxyacyl-CoA undergoes dehydrogenation during beta-oxidation?

    <p>3-ketoacyl-CoA</p> Signup and view all the answers

    During the complete beta-oxidation of a long-chain fatty acid, what is the outcome of each cycle in terms of products created?

    <p>1 Acetyl-CoA and 1 FADH2</p> Signup and view all the answers

    What role does thiolase play in the beta-oxidation pathway?

    <p>Cleaves 3-ketoacyl-CoA to generate Acetyl-CoA</p> Signup and view all the answers

    Which compound remains at the end of fatty acid oxidation for odd-chain fatty acids?

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

    How many cycles of beta-oxidation are required to completely oxidize palmitate (C16)?

    <p>7</p> Signup and view all the answers

    What is the total gross ATP yield from the complete oxidation of palmitate, after considering activation energy?

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

    Which coenzyme is specifically involved in the conversion of 3-hydroxyacyl-CoA to its corresponding 3-keto derivative?

    <p>NAD+</p> Signup and view all the answers

    What is the end product of the complete oxidation pathway for a C16 fatty acid in terms of ATP production?

    <p>80 ATP</p> Signup and view all the answers

    What is the significance of the propionyl residue that remains after the beta-oxidation of odd-chain fatty acids?

    <p>It is used to synthesize glucose.</p> Signup and view all the answers

    In beta-oxidation, how many moles of NADH are generated from the complete oxidation of palmitate?

    <p>7</p> Signup and view all the answers

    Match the ketone bodies with their corresponding properties:

    <p>Acetoacetate = Direct product of fatty acid oxidation D-3-Hydroxybutyrate = Used as a fuel by extrahepatic tissues Acetone = Volatile and not used for energy Ketone bodies = Produced during high rates of fatty acid oxidation</p> Signup and view all the answers

    Match the stages of fatty acid metabolism with their descriptions:

    <p>Activation = Process of preparing fatty acids for transport β-oxidation = Pathway for breaking down fatty acids to acetyl-CoA Ketogenesis = Production of ketone bodies in the liver Fatty acid synthesis = Formation of fatty acids from acetyl-CoA</p> Signup and view all the answers

    Match the conditions with their effects on ketone body production:

    <p>High fatty acid oxidation = Increased ketone body synthesis Prolonged fasting = Leads to ketosis Diabetes = Causes excessive ketone body production Normal metabolism = Utilization of ketone bodies for energy</p> Signup and view all the answers

    Match the terms with their corresponding definitions:

    <p>Acetyl-CoA = End product of fatty acid oxidation Ketosis = Excessive accumulation of ketone bodies Ketoacidosis = Pathological condition from prolonged ketosis Mitochondria = Site of fatty acid oxidation</p> Signup and view all the answers

    Match the enzymes with their roles in fatty acid metabolism:

    <p>Carnitine acyltransferase = Transfers acyl groups from CoA to carnitine Acyl-CoA dehydrogenase = Catalyzes the initial step of β-oxidation β-hydroxyacyl-CoA dehydrogenase = Converts D-3-hydroxybutyrate to acetoacetate Thiolase = Cleaves acyl-CoA to form acetyl-CoA</p> Signup and view all the answers

    Match the following enzymes with their functions in the β-oxidation pathway:

    <p>Acyl-CoA dehydrogenase = Removes hydrogen atoms and forms FADH2 Carnitine palmitoyltransferase-I = Transfers acyl groups from CoA to carnitine Carnitine palmitoyltransferase-II = Reforms acyl-CoA from acylcarnitine Translocase = Transports acylcarnitine into the mitochondrial matrix</p> Signup and view all the answers

    Match the following products to their sources in the β-oxidation pathway:

    <p>Acetyl-CoA = Formed from cleavage of fatty acyl-CoA FADH2 = Generated during the oxidation of acyl-CoA NADH = Produced in later steps of fatty acid oxidation Acylcarnitine = Formed during the transfer of acyl groups to carnitine</p> Signup and view all the answers

    Match the following statements with their corresponding terms in β-oxidation:

    <p>Triglycerides = Storage form of fatty acids Acyl-CoA = Activated fatty acid for oxidation β-Oxidation = Process of breaking down fatty acids Cyclic pathway = Describes the repetitive nature of β-oxidation</p> Signup and view all the answers

    Match the following fatty acids with their number of Acetyl-CoA produced during β-oxidation:

    <p>Palmitic acid (C16) = 8 Acetyl-CoA Stearic acid (C18) = 9 Acetyl-CoA Oleic acid (C18:1) = 9 Acetyl-CoA Lauric acid (C12) = 6 Acetyl-CoA</p> Signup and view all the answers

    Match the following outcomes to their respective processes in β-oxidation:

    <p>NADH and FADH2 generation = Result of acyl-CoA oxidation ATP formation = Outcome of oxidative phosphorylation Transport of long-chain fatty acids = Involves carnitine Removal of two carbons = Occurs in each cycle of β-oxidation</p> Signup and view all the answers

    Study Notes

    Oxidation of Fatty Acids: Ketogenesis

    • Fatty acids are broken down in mitochondria to acetyl-CoA, producing large amounts of energy.
    • When fatty acid oxidation is high, the liver produces ketone bodies (acetoacetate, D-3-hydroxybutyrate, acetone).
    • Ketone bodies are used as fuels by other tissues.
    • Excessive ketone body production leads to ketosis, potentially life-threatening ketoacidosis.
    • Fatty acid oxidation is crucial for gluconeogenesis. Impairments cause hypoglycemia.
    • Fatty acid oxidation occurs in mitochondria, a different compartment from fatty acid synthesis.
    • Fatty acids are transported in the blood as free fatty acids bound to albumin.
    • Fatty acids must be activated (converted to acyl-CoA) before breakdown. This step requires ATP.
    • Acyl-CoA synthetase catalyzes this activation process.
    • Activated fatty acids cannot directly cross the inner mitochondrial membrane.
    • Carnitine shuttles fatty acids across the membrane as acylcarnitine.
    • Carnitine palmitoyltransferase-I transfers acyl groups from CoA to carnitine.
    • Acylcarnitine crosses the inner membrane via a transporter.
    • Carnitine palmitoyltransferase-II transfers acyl groups back to CoA.
    • Beta-oxidation is a process of cleaving two carbons at a time from acyl-CoA.
    • Each cycle of beta-oxidation yields one FADH₂ and one NADH, supplying ATP through oxidative phosphorylation.
    • Palmitate (C16) yields 8 acetyl-CoA molecules, generating a large quantity of ATP.
    • Peroxisomes modify beta-oxidation, oxidizing very long-chain fatty acids.
    • Unsaturated fatty acids have modified beta-oxidation pathways.
    • Ketogenesis occurs during high rates of fatty acid oxidation.
    • Acetoacetyl-CoA is formed from two acetyl-CoA molecules via HMG-CoA synthase.
    • Acetoacetyl-CoA is split into acetoacetate (converted to acetone) and 3-hydroxybutyrate.
    • Ketone bodies are used as fuel in extrahepatic tissues.
    • Excess ketone bodies are eliminated from the body.
    • Ketogenesis is regulated at 3 steps.
    • Control of free fatty acid mobilization from adipose tissue.
    • CPT-I activity in liver: determining the proportion of fatty acids that undergo oxidation or are esterified.
    • Partition of acetyl-CoA between ketogenesis and the citric acid cycle.
    • Impaired fatty acid oxidation can cause hypoglycemia, organ fat buildup, and hypoketonemia.
    • Ketosis is mild in starvation, but can be severe in diabetes mellitus and some other conditions.

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