Biochemistry: Fatty Acid Oxidation
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Biochemistry: Fatty Acid Oxidation

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Questions and Answers

What is the role of bile salts in lipid digestion?

  • They convert lipids into water-soluble forms immediately.
  • They hydrolyze triglycerides into fatty acids.
  • They emulsify lipids to enhance enzyme access. (correct)
  • They absorb lipids directly into the bloodstream.

    • What is formed during the emulsification of triglycerides by bile salts?

  • Large lipid droplets suspended in water.
  • Fatty acids and cholesterol only.
  • Mixed micelles including lipids and bile salts. (correct)
  • Glycerol and water-soluble fatty acids.

    • What happens to bile salts during the absorption of lipids?

  • They are absorbed along with fatty acids.
  • They remain in the intestinal mucosa.
  • They are converted into fatty acids and glycerol.
  • They dissociate from micelles and stay in the lumen. (correct)

    • What results from a blockage in the biliary duct?

    <p>Steatorrhoea characterized by pale, bulky stools.</p> Signup and view all the answers

    Which component is NOT typically found in a mixed micelle during lipid absorption?

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

    What is a primary role of fatty acids and their derivatives in biological systems?

    <p>They are used for high energy storage.</p> Signup and view all the answers

    Which class of lipids is characterized by the presence of glycerol and fatty acids?

    <p>Esters of fatty acids and glycerol</p> Signup and view all the answers

    Why are lipids effective insulators in biological systems?

    <p>Their hydrophobic nature reduces heat exchange.</p> Signup and view all the answers

    What is the classification basis for lipids compared to other biomolecules?

    <p>Physical properties, especially solubility in organic solvents</p> Signup and view all the answers

    Which of the following is a common use of lipids in humans?

    <p>For protection against loss of moisture</p> Signup and view all the answers

    Which group of lipids acts as signaling molecules?

    <p>Steroid hormones</p> Signup and view all the answers

    What is a characteristic of triglycerides compared to glycogen?

    <p>They store more energy per weight.</p> Signup and view all the answers

    Which of the following vitamins is fat-soluble?

    <p>Vitamin D</p> Signup and view all the answers

    What is the total ATP yield from the complete oxidation of one molecule of Palmitoyl-CoA?

    <p>130 ATP</p> Signup and view all the answers

    How many ATP are generated per carbon atom oxidized from Palmitic acid?

    <p>8.1</p> Signup and view all the answers

    What is the first step in the oxidation of odd-numbered fatty acids?

    <p>Activation to fatty acyl-CoA</p> Signup and view all the answers

    What compound must be further catabolized after oxidation to enter the citric acid cycle?

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

    Which enzyme is involved in the final oxidation of propionyl-CoA?

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

    What happens when there is a defect in mutase activity concerning propionyl-CoA metabolism?

    <p>Methylmalonyl-CoA concentrations increase</p> Signup and view all the answers

    What is the significance of reduced flavoproteins (FAD) in ATP generation during fatty acid oxidation?

    <p>Each FAD yields 2 ATP through electron transport</p> Signup and view all the answers

    What is the primary reason for the higher energy yield from fatty acid oxidation compared to carbohydrate oxidation?

    <p>Higher number of carbons in fatty acids</p> Signup and view all the answers

    What percentage of dietary fat is constituted by triacylglycerides?

    <p>More than 90%</p> Signup and view all the answers

    Which of the following lipids are soluble in organic solvents?

    <p>All of the above</p> Signup and view all the answers

    How do bile salts facilitate lipid digestion?

    <p>By emulsifying fat to form micelles</p> Signup and view all the answers

    What is the role of the carboxyl group in bile acids?

    <p>It is often conjugated to form bile salts</p> Signup and view all the answers

    Which enzymes are involved in the digestion of emulsified lipids?

    <p>Pancreatic lipase</p> Signup and view all the answers

    What is a primary source of triacylglycerols for the body?

    <p>Dietary intake</p> Signup and view all the answers

    What structural feature gives bile salts their emulsifying properties?

    <p>A hydrophobic surface and a hydrophilic surface</p> Signup and view all the answers

    What is the significance of micelles formed by bile salts?

    <p>They allow digestive enzymes to effectively access lipids</p> Signup and view all the answers

    What is the primary site of triacylglycerol digestion?

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

    What enzyme is primarily responsible for hydrolysing triacylglycerol?

    <p>Pancreatic lipase</p> Signup and view all the answers

    Which component forms mixed micelles along with monoacylglycerols and fatty acids?

    <p>Bile salts</p> Signup and view all the answers

    What would likely occur in patients with an abnormally low concentration of bile salts?

    <p>Increased steatorrhoea</p> Signup and view all the answers

    What is a common cause of reduced bile salt concentration in the intestine?

    <p>Biliary obstruction</p> Signup and view all the answers

    What happens to fatty acids after absorption into intestinal epithelial cells?

    <p>They are re-esterified to form triacylglycerols.</p> Signup and view all the answers

    Which vitamins are notably at risk of deficiency in patients with low bile salt concentrations?

    <p>Vitamins A, D, E, and K</p> Signup and view all the answers

    What is the purpose of bile salt micelles in the digestion process?

    <p>To stabilize lipid molecules in water.</p> Signup and view all the answers

    Study Notes

    Fatty Acid Oxidation

    • Palmitoyl-CoA (16 carbon fatty acid) degrades to 8 mol of acetyl-CoA.
    • Balanced equation for oxidation:
      • Palmitoyl-CoA + 7CoA-SH + 7FAD + 7NAD+ + 7H2O → 8 acetyl-CoA + 7FADH2 + 7NADH + H+.
    • Each FADH2 produces 2 ATP and each NADH produces 3 ATP, totaling 35 ATP from reduced cofactors.
    • Oxidation of 8 acetyl-CoA through the TCA cycle yields 96 ATP.
    • Net ATP yield from one palmitic acid: 130 ATP (35 + 96 - 1 for activation).
    • ATP yield per carbon oxidized: approximately 8.1 (130/16).
    • For comparison, glucose yields 6 ATP per 6 carbons oxidized.

    Odd-Numbered Fatty Acid Oxidation

    • Odd-numbered fatty acids are oxidized similarly to even-numbered, starting at the carboxyl end.
    • Final cycle features a 5-carbon acyl-CoA (Butyryl-CoA).
    • Cleavage yields acetyl-CoA (2C) and propionyl-CoA (3C).
    • Acetyl-CoA is fully oxidized; propionyl-CoA requires further catabolism.
    • Increased methylmalonyl-CoA due to defective mutase or vitamin B12 deficiency leads to severe acidosis.

    Lipids Overview

    • Organic molecules, soluble in non-polar solvents, sparingly soluble in water.
    • Serve protective roles (moisture retention in birds, humans, camels).
    • Provide energy in diets through sources like oils and margarine.

    Lipid Classes

    • Classified based on solubility:
      • Fatty acids (saturated, unsaturated, eicosanoids).
      • Esters of fatty acids and glycerol (triglycerides, phosphoglycerides).
      • Lipids without glycerols (sphingolipids).
      • Sterols (cholesterol, steroid hormones, vitamin D).
      • Terpene and isoprenoid derivatives.

    Functions of Lipids

    • Serve as high-energy storage, yielding 6 times more energy than glycogen.
    • Provide insulation and reduced heat exchange via adipose tissue.
    • Form hydrophobic barriers in cellular membranes.
    • Act as signaling molecules (prostaglandins, steroids) and enzyme cofactors.
    • Precursors to fat-soluble vitamins (A, D, E, K).

    Lipid Digestion and Absorption

    • 90% of dietary lipids are triglycerides (TAGs).
    • Digestion begins in the stomach but is limited due to aggregation.
    • Bile salts (detergent action) emulsify TAGs, aiding fat digestion.

    Role of Bile Salts

    • Bile salts possess both hydrophobic and hydrophilic surfaces, allowing for emulsification at the oil-water interface.
    • Form micelles, facilitating digestion by water-soluble pancreatic lipases and absorption into intestinal mucosa.

    Lipase Action

    • Lipases hydrolyze ester linkages in TAGs, producing monoacylglycerol and fatty acids.
    • Stable interaction with water is necessary for absorption.

    Clinical Implications

    • Conditions such as biliary duct obstruction lead to steatorrhea (bulky, oily stools).
    • Inadequate bile salts affect absorption of fat-soluble vitamins, potentially leading to deficiencies.
    • Patients may require dietary modifications and vitamin supplementation through injection.

    Post-Absorption

    • Inside intestinal epithelial cells, fatty acids are re-esterified into triglycerides after absorption.

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    Description

    This quiz covers the stages of fatty acid oxidation, focusing on the degradation of Palmitoyl-CoA to acetyl-CoA. It includes details about the balanced equation and the ATP yield from reduced flavoproteins and nucleotides. Test your understanding of metabolic pathways and energy production in biochemistry.

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