Lipid Metabolism: TAGs and Fatty Acids
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Questions and Answers

What is the main storage form for fats in the body?

  • Chylomicrons
  • Fatty acids
  • Glycerol-3-P
  • Triacylglycerols (correct)

    • Which enzyme is responsible for mobilizing fatty acids from triacylglycerol stores?

  • FA synthase
  • Acetyl-CoA carboxylase
  • Hormone-dependent lipase (correct)
  • β-oxidation enzyme

    • During which metabolic process are fatty acids degraded to acetyl-CoA?

  • Gluconeogenesis
  • FA synthesis
  • β-oxidation (correct)
  • Lipogenesis

    • What substance serves as the substrate for fatty acid synthesis in the cytoplasm?

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

    Which of the following statements is true regarding the regulation of fatty acid synthesis?

    <p>It involves subcellular compartmentalization and tissue specialization.</p> Signup and view all the answers

    Where does fatty acid synthesis primarily take place?

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

    What is the activated donor of 2 carbon units in fatty acid synthesis?

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

    Which enzyme's reaction is the rate-limiting step in fatty acid synthesis?

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

    Which molecule provides the reducing power during fatty acid synthesis?

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

    Which hormone acts as an allosteric activator of acetyl CoA carboxylase in a fed state?

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

    What is the final product of the fatty acid synthesis pathway as it relates to palmitate?

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

    How many ATP molecules are required to form palmitate?

    <p>42 ATP</p> Signup and view all the answers

    In fatty acid degradation, what molecule is primarily released as units of 2 carbons?

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

    What role does malonyl CoA play during fatty acid synthesis?

    <p>It inhibits FA-carnitine formation and mitochondrial entry of fatty acids.</p> Signup and view all the answers

    Where does most fatty acid synthesis occur in the body?

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

    What effect does high cytoplasmic citrate have on fatty acid synthesis?

    <p>It stimulates acetyl CoA carboxylase to increase FA synthesis.</p> Signup and view all the answers

    Which of the following hormones is associated with the inhibition of fatty acid synthesis?

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

    What happens to fatty acids mobilized from adipose tissue during starvation?

    <p>They are distributed throughout the body bound to serum albumin.</p> Signup and view all the answers

    What is the primary function of acetyl-CoA produced from fatty acid oxidation?

    <p>It contributes to the synthesis of ketone bodies.</p> Signup and view all the answers

    Which enzyme is stimulated by insulin to increase fatty acid synthesis?

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

    How does the enzyme system on the endoplasmic reticulum contribute to fatty acid metabolism?

    <p>It adds C-C units from malonyl CoA and introduces double bonds.</p> Signup and view all the answers

    What is the main reason triacylglycerols have a higher energy content compared to carbohydrates?

    <p>They are highly reduced and hydrophobic.</p> Signup and view all the answers

    In which part of the body are most fatty acids synthesized?

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

    What substance is primarily responsible for the mobilization of fatty acids from adipose tissue?

    <p>Hormone-dependent lipase</p> Signup and view all the answers

    What happens to fatty acids to prepare them for oxidation in the mitochondria?

    <p>They are conjugated with CoASH.</p> Signup and view all the answers

    Which statement about the energy content of fats and carbohydrates is correct?

    <p>Fats provide about 9 kcal/gm of energy.</p> Signup and view all the answers

    What is the role of carnitine in fatty acid metabolism?

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

    Which hormones are primarily responsible for activating the degradation of fatty acids?

    <p>Glucagon and epinephrine</p> Signup and view all the answers

    What portion of fat is considered gluconeogenic?

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

    What is the result of the cleavage of 3-ketoacyl CoA by CoASH?

    <p>Acetyl CoA + acyl CoA (- 2 C)</p> Signup and view all the answers

    Which vitamin deficiency leads to the accumulation of methylmalonyl CoA?

    <p>Vitamin B12</p> Signup and view all the answers

    What is the total ATP yield from the complete oxidation of palmitate (C16)?

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

    Which of the following reactions occurs first in the ß-oxidation pathway?

    <p>Reduction of FAD</p> Signup and view all the answers

    During which metabolic condition do ketone bodies form in the mitochondrial matrix?

    <p>During fasting</p> Signup and view all the answers

    How is energy generated from the oxidation of fatty acids?

    <p>By forming acetyl CoA and entering the citric acid cycle</p> Signup and view all the answers

    What occurs when lipolysis and ß-oxidation are elevated in the liver?

    <p>Formation of ketone bodies</p> Signup and view all the answers

    How many NADH are produced during the oxidation of each molecule of palmitate?

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

    Study Notes

    Lipid Metabolism 1: Triacylglycerols and Fatty Acids

    • Triacylglycerols (TAGs) are the primary storage form of lipids, more efficient than carbohydrates or proteins for energy storage
    • TAGs are composed of three fatty acids and glycerol
    • Fatty acids are either saturated or unsaturated
    • Dietary fats are broken down to fatty acids (FAs) and repackaged as TAGs in chylomicrons
    • FAs are mobilized from adipose tissue by hormone-dependent lipase (in response to glucagon and catecholamines)
    • FA degradation occurs in the mitochondrial matrix via beta-oxidation
    • Fatty acid synthesis occurs in the cytosol
    • Entry of fatty acids into the mitochondria is a key regulatory step for degradation
    • Excess acetyl-CoA from FA oxidation can be converted to ketone bodies during starvation; these are used as alternative fuels for certain tissues
    • Odd-chain fatty acids are metabolized to succinyl-CoA via a vitamin B12-dependent process
    • Fatty acid synthesis and degradation are regulated by subcellular compartments, tissue specialization, and hormones (phosphorylation/dephosphorylation)

    Fatty Acid Degradation

    • Degradation of fatty acids occurs in two-carbon units
    • Beta-oxidation is the process of breaking down fatty acids in mitochondria
    • Beta-oxidation pathways are similar to the last three steps of the citric acid cycle (succinate, fumarate, malate, and oxaloacetate)
    • Fatty acids are degraded 2 carbons at a time, producing Acetyl-CoA as a key intermediate

    Fatty Acid Synthesis

    • Fatty acid synthesis occurs in the cytosol

    • It uses malonyl-CoA as a two-carbon building block

    • It requires NADPH as a reducing agent

    • Acetyl-CoA carboxylase is the rate-limiting enzyme of fatty acid synthesis

    • Requires biotin as a cofactor

    • Regulation of acetyl-CoA carboxylase is dependent on phosphorylation/dephosphorylation

    • Allosteric activation by citrate is observed; inhibition by product palmitoyl CoA

    • Inhibition by glucagon and catecholamines

    • Phosphorylated form of enzyme shows a smaller stimulatory response to citrate.

    • Insulin (+) regulates the enzyme by promoting dephosphorylation

    Fatty Acid Synthesis and Degradation Differences

    • Synthesis occurs in the cytosol; degradation in the mitochondrial matrix
    • Synthesis uses acyl carrier protein (ACP); degradation uses acyl-CoA
    • Synthesis uses malonyl-CoA as a two-carbon unit donor; degradation releases two-carbon units as acetyl-CoA
    • Synthesis uses NADPH as a reducing agent; degradation produces NADH and FADH2

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    Lipid Metabolism 1: Triacylglycerols and Fatty Acids PDF

    Description

    This quiz covers the essential aspects of lipid metabolism, focusing on triacylglycerols (TAGs) and fatty acids. Explore how TAGs serve as energy storage, the processes of fatty acid synthesis and degradation, and the metabolic pathways involved. Test your understanding of the regulation and functions of fatty acids in the body.

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