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Questions and Answers
What is the primary location for β-oxidation of fatty acids?
What is the primary location for β-oxidation of fatty acids?
Which of the following enzymes is responsible for the activation of fatty acids?
Which of the following enzymes is responsible for the activation of fatty acids?
What role does the carnitine shuttle play in β-oxidation?
What role does the carnitine shuttle play in β-oxidation?
Which of the following conditions is likely to increase β-oxidation of fatty acids?
Which of the following conditions is likely to increase β-oxidation of fatty acids?
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What is the effect of insulin on β-oxidation?
What is the effect of insulin on β-oxidation?
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What is the primary site for the synthesis of ketone bodies?
What is the primary site for the synthesis of ketone bodies?
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Which of the following pathways is NOT involved in the formation of acetoacetate from acetoacetyl CoA?
Which of the following pathways is NOT involved in the formation of acetoacetate from acetoacetyl CoA?
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What regulates the entry of long-chain acyl CoA into the mitochondria for β-oxidation?
What regulates the entry of long-chain acyl CoA into the mitochondria for β-oxidation?
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How does starvation affect the production of ketone bodies?
How does starvation affect the production of ketone bodies?
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What is the maximum concentration of ketone bodies that can typically be found in the blood?
What is the maximum concentration of ketone bodies that can typically be found in the blood?
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Which condition leads to a decrease in ketogenesis?
Which condition leads to a decrease in ketogenesis?
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What is the first step in the formation of acetoacety CoA during ketogenesis?
What is the first step in the formation of acetoacety CoA during ketogenesis?
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What is a potential outcome of spontaneous decarboxylation of acetoacetic acid?
What is a potential outcome of spontaneous decarboxylation of acetoacetic acid?
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How many total ATP are produced after β-oxidation of palmitic acid and subsequent Kreb's cycle processing?
How many total ATP are produced after β-oxidation of palmitic acid and subsequent Kreb's cycle processing?
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What is the role of propionyl CoA in the oxidation of odd-numbered fatty acids?
What is the role of propionyl CoA in the oxidation of odd-numbered fatty acids?
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Which type of fatty acid oxidation mainly occurs in the brain and liver and does not generate energy?
Which type of fatty acid oxidation mainly occurs in the brain and liver and does not generate energy?
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What is the formula to calculate the energy produced from even-numbered fatty acids?
What is the formula to calculate the energy produced from even-numbered fatty acids?
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What are the three substances that comprise ketone bodies produced during high rates of fatty acid oxidation?
What are the three substances that comprise ketone bodies produced during high rates of fatty acid oxidation?
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What is a key feature of α-oxidation in fatty acid metabolism?
What is a key feature of α-oxidation in fatty acid metabolism?
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What happens to excess acetyl-CoA during high fatty acid oxidation in the liver?
What happens to excess acetyl-CoA during high fatty acid oxidation in the liver?
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Which of the following describes the fate of β-oxidation products derived from palmitic acid?
Which of the following describes the fate of β-oxidation products derived from palmitic acid?
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Study Notes
Fatty Acid Oxidation
- Oxidation of fatty acids provides the most energy compared to other food, with 1 gram of fat producing approximately 9 Kcal.
- Fatty acids derive from diet or mobilization from adipose tissue through lipolysis.
- Types of fatty acid oxidation include beta (β) oxidation (most common), alpha (α) oxidation, and omega (ω) oxidation.
Beta-Oxidation
- Site: Occurs intracellularly within mitochondria in organs like liver, kidney, and heart.
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Steps:
- Activation: Fatty acids are activated in the cytoplasm by acyl-CoA synthetase (or thiokinase), requiring ATP, to form acyl-CoA.
- Transport: Acyl-CoA is transported into the mitochondria via a carnitine shuttle. This involves three enzymes: carnitine acyltransferase I (in outer membrane), carnitine acylcarnitine translocase (inner membrane), and carnitine acyltransferase II (inner membrane).
- Oxidation: Oxidation occurs in the mitochondrial matrix involving a series of reactions: dehydrogenases, hydratases, and thiolases. These steps produce acetyl-CoA, FADH2, and NADH.
Energy Production from β-oxidation of Palmitic Acid
- Palmitic acid (a saturated fatty acid) undergoes β-oxidation 7 times.
- Each cycle generates one FADH2 and one NADH + H+.
- Acetyl-CoA produced enters the Krebs cycle, generating 12 ATP per molecule.
- 7 cycles of β-oxidation yield 7 FADH2 and 7 NADH+H.
- 8 molecules of Acetyl-CoA are produced, generating 96 ATP.
- Activation of palmitic acid requires 2 ATP.
Regulation of FA Oxidation
- β-oxidation increases during decreased glucose oxidation (e.g., in diabetes mellitus and starvation).
- This is linked to increased lipolysis, releasing fatty acids into the blood.
- β-oxidation is inhibited by insulin and carbohydrate-rich meals. In these states, glucose oxidation is favoured, and fatty acid release is decreased.
Oxidation of Odd Number Fatty Acids
- Odd-numbered fatty acids are oxidized through beta-oxidation.
- The final 3-carbon molecule (propionyl-CoA) is converted to succinyl-CoA.
- Succinyl-CoA enters the citric acid cycle and can be used for gluconeogenesis.
Alpha (α) Oxidation
- Occurs primarily in the brain and liver, but is a minor pathway.
- Removes one carbon at a time from the carbon position.
- It does not utilize CoA and doesn't generate significant energy.
- Important for the metabolism of dietary methylated fatty acids, for example phytanic acid (found in ruminants and dairy products).
Metabolism of Ketone Bodies
- During high rates of fatty acid oxidation (especially in the liver), acetyl-CoA production exceeds the capacity of the citric acid cycle. This leads to the synthesis of ketone bodies.
- Ketone bodies (acetoacetic acid, β-hydroxybutyric acid, and acetone) are exported to extrahepatic tissues as a fuel source.
- Important fuel during prolonged fasting and starvation especially for the brain.
Ketone Body Synthesis (Ketogenesis)
- Definition: Ketogenesis is the synthesis of ketone bodies from acetyl CoA.
- Site: Occurs in the mitochondria of liver cells.
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Steps:
- Acetoacetyl-CoA forms from two acetyl-CoA molecules (directly or through beta-oxidation).
- Acetoacetate is produced from acetoacetyl-CoA.
- Acetoacetate can be converted to acetone or β-hydroxybutyrate.
Regulation of Ketogenesis
- Ketogenesis is increased by lipolysis (breakdown of fats) in adipose tissue, rising free fatty acid (FFA) levels, and increased FFA uptake by the liver.
- Increased activity of carnitine palmitoyl transferase-1 in the liver facilitates the transport of fatty acids into the mitochondria for oxidation, thus enhancing ketogenesis.
- Malonyl-CoA, an inhibitor of fatty acid transport, suppresses ketogenesis in the fed state (sufficient glucose intake).
- Starvation conditions lead to reduced inhibition and elevated ketogenesis.
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Description
Test your knowledge on the oxidation of fatty acids, which is crucial for energy production in the body. This quiz covers the processes of beta-oxidation, activation, and transport of fatty acids within the mitochondria. Understand the different types of fatty acid oxidation and their significance in metabolism.
