Biochemistry Chapter 14: Fat as Fuel
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Questions and Answers

What is the primary function of carnitine acyltransferase I in the transport of fatty acids into mitochondria?

  • To transfer the fatty acid group to carnitine, creating fatty acyl-carnitine (correct)
  • To recreate fatty acyl-CoA from fatty acyl-carnitine
  • To oxidize the β-carbon, producing a carbonyl group
  • To facilitate the crossing of fatty acyl-carnitine into the inner mitochondrial membrane

    • What is the net result of one round of β-oxidation?

  • The production of acetyl-CoA and a fatty acyl-CoA that is 4 carbons shorter
  • The production of acetyl-CoA and a fatty acyl-CoA that is 3 carbons shorter
  • The production of acetyl-CoA and a fatty acyl-CoA that is 2 carbons shorter (correct)
  • The production of acetyl-CoA and a fatty acyl-CoA that is 1 carbon shorter

    • What is the purpose of the translocase in the transport of fatty acids into mitochondria?

  • To oxidize the β-carbon, producing a carbonyl group
  • To transfer the fatty acid group to carnitine, creating fatty acyl-carnitine
  • To facilitate the crossing of fatty acyl-carnitine into the inner mitochondrial membrane (correct)
  • To recreate fatty acyl-CoA from fatty acyl-carnitine

    • What is the function of carnitine acyltransferase II in the transport of fatty acids into mitochondria?

    <p>To recreate fatty acyl-CoA from fatty acyl-carnitine</p> Signup and view all the answers

    What is the name of the process by which fatty acids are broken down in the mitochondria?

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

    Why is the process of β-oxidation called as such?

    <p>Because it involves the oxidation of the β-carbon</p> Signup and view all the answers

    What is the primary function of adipose tissue lipase?

    <p>To break down triglycerides into fatty acids and glycerol</p> Signup and view all the answers

    What is the purpose of the carnitine shuttle system?

    <p>To transport fatty acids from the cytosol to the mitochondria</p> Signup and view all the answers

    What is the end product of the β-oxidation pathway?

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

    What is the significance of ketogenesis in starvation?

    <p>It provides a alternative source of energy during starvation</p> Signup and view all the answers

    What is the role of cholesterol in the biological functions of lipids?

    <p>It is a precursor to steroid hormones</p> Signup and view all the answers

    What is the function of arachidonic acid in the biological functions of lipids?

    <p>It is a precursor to prostaglandins</p> Signup and view all the answers

    What is the primary function of triglycerides in the body?

    <p>To store energy for long-term use</p> Signup and view all the answers

    What is the role of fatty acids in the biological functions of lipids?

    <p>They are activated to their CoA esters and transported into the mitochondria</p> Signup and view all the answers

    What is the approximate energy yield of 1 gram of fat?

    <p>38 kJ</p> Signup and view all the answers

    Which of the following is NOT a common fatty acid?

    <p>Glutamic acid</p> Signup and view all the answers

    What is the byproduct of the breakdown of triglycerides in adipose tissue?

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

    In which tissue is glycerol primarily taken up and converted to glucose?

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

    What is the primary function of the carnitine shuttle?

    <p>To transport fatty acids into the mitochondria</p> Signup and view all the answers

    What is the net result of the beta-oxidation pathway?

    <p>The breakdown of fatty acids into acetyl-CoA</p> Signup and view all the answers

    What is the byproduct of the activation of long-chain fatty acids?

    <p>AMP and PPi</p> Signup and view all the answers

    What is the function of CoA-SH in the activation of fatty acids?

    <p>To form a thioester bond with the fatty acid</p> Signup and view all the answers

    What is the primary advantage of storing energy as triglycerides?

    <p>They are more compactly stored</p> Signup and view all the answers

    What is the role of lipase in the breakdown of triglycerides?

    <p>To break down triglycerides into fatty acids and glycerol</p> Signup and view all the answers

    What is the result of Reaction 1 in the β-oxidation pathway?

    <p>Removal of 2 hydrogens and cleavage of a bond</p> Signup and view all the answers

    What is the purpose of the carnitine shuttle?

    <p>To transport fatty acids into the mitochondria</p> Signup and view all the answers

    What is the ATP yield from the complete oxidation of a fatty acid with 16 carbon atoms?

    <p>107 ATP</p> Signup and view all the answers

    What is the end product of β-oxidation that enters the TCA cycle?

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

    What is the purpose of the electron transport chain in β-oxidation?

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

    What is the fate of the last 3 carbons of an odd-numbered fatty acid?

    <p>They are converted to methylmalonyl-CoA</p> Signup and view all the answers

    What is the purpose of the enzyme Propionyl-CoA-carboxylase?

    <p>To convert propionyl-CoA to methylmalonyl-CoA</p> Signup and view all the answers

    What is the condition under which ketogenesis occurs?

    <p>When the TCA cycle is overloaded with acetyl-CoA</p> Signup and view all the answers

    What is the result of Reaction 4 in the β-oxidation pathway?

    <p>Removal of 2 carbon units and the formation of acetyl-CoA</p> Signup and view all the answers

    What is the purpose of the enzyme enoyl-CoA hydratase?

    <p>To convert enoyl-CoA to hydroxyacyl-CoA</p> Signup and view all the answers

    What is the primary destination of acetoacetate and β hydroxybutyrate released from the liver?

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

    Why can't the liver utilize ketone bodies?

    <p>It is specialized to produce ketone bodies, not utilize them</p> Signup and view all the answers

    What is the primary source of energy for red blood cells?

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

    What is the fate of acetoacetate and β hydroxybutyrate in most tissue cells?

    <p>They are converted back to TCA cycle intermediates</p> Signup and view all the answers

    What is the role of ketone bodies in the brain?

    <p>Emergency fuel source</p> Signup and view all the answers

    What is the fate of excess acetyl-CoA in the liver?

    <p>It is converted to ketone bodies</p> Signup and view all the answers

    Which of the following tissues can utilize both fatty acids and ketone bodies for energy?

    <p>Most tissue cells</p> Signup and view all the answers

    What is the primary reason why the brain cannot utilize fatty acids for energy?

    <p>Inability to cross the blood-brain barrier</p> Signup and view all the answers

    Study Notes

    Biological Functions of Lipids

    • Components of cell membranes (phospholipids and cholesterol)
    • Precursors of hormones (cholesterol and arachidonic acid)
    • Long-term fuels (triglycerides)

    Efficiency of Triglycerides as Fuel

    • Compact storage: large fat droplets in adipose tissue cells
    • Large body stores: 11 kg fat (as triglycerides) in a 70 kg adult
    • Efficiency on weight basis: 1 g fat yields 38 kJ, compared to 1 g protein (21 kJ) and 1 g carbohydrate (17 kJ)

    Structure of Triglyceride Fat

    • Glycerol component of triacylglycerol
    • Common fatty acids: palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), and linoleic acid (C18:2)

    Breakdown of Stored Triglyceride Fat in Adipose Tissue

    • Lipase (activated by adrenaline and glucagon) breaks down triglyceride into fatty acids and glycerol
    • Fatty acids travel in the plasma bound to albumin
    • Glycerol diffuses into the bloodstream and is taken up by the liver for glycolysis

    Metabolism of Glycerol

    • Glycerol is water-soluble and taken up by all tissues
    • In liver, glycerol enters glycolysis and is converted to pyruvate, then into the TCA cycle for oxidation

    Fatty Acid Metabolism by β-Oxidation Pathway

    • Occurs in the mitochondrial matrix
    • Biological energy of fatty acid molecule is conserved as the transfer of 2 H atoms to the cofactors NAD+ and FAD
    • Series of four enzyme reactions result in the removal of a 2-carbon unit as acetyl CoA

    Activation of Long-Chain Fatty Acids

    • Fatty acyl-CoA synthetase catalyzes the reaction between fatty acids and CoA
    • Forms a thioester bond between the fatty acid and CoA

    Transport of Fatty Acyl-CoA into Mitochondria: Carnitine Shuttle

    • Fatty acyl-CoA is converted into fatty acyl-carnitine, which crosses the inner mitochondrial membrane via a translocase
    • Carnitine is switched back for CoA by carnitine acyltransferase II

    β-Oxidation Pathway

    • Fatty acyl-CoA with 10 carbons undergoes β-oxidation
    • One round of β-oxidation produces acetyl CoA and a fatty acyl-CoA that is 2 carbons shorter
    • The process is energetically neutral

    Regulation of Fat Metabolism

    • Release of fatty acids from adipose tissue (adrenaline and glucagon activate lipase enzyme)
    • Rate of entry into mitochondria via carnitine shuttle
    • Rate of reoxidation of cofactors NADH and FADH2 by Electron Transport Chain

    Metabolism of Odd-Numbered Fatty Acids

    • β-Oxidation results in the production of propionyl-CoA
    • Propionyl-CoA is converted into succinyl-CoA, which enters the TCA cycle

    Ketone Body Formation

    • Occurs when fat metabolism is the main source of energy (starvation, Type I diabetes)
    • Fatty acid oxidation in hepatocytes leads to high concentrations of Acetyl CoA, which is converted into ketone bodies (acetoacetate and β-hydroxybutyrate) in the liver
    • Ketone bodies can be utilized for energy by most tissues, but not the liver

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    Description

    Learn about the role of fat as fuel in biochemistry and molecular biology. This lecture covers the basics of fat metabolism and its importance in nutrition.

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