Biosynthesis of Fatty Acids
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Questions and Answers

What is the primary substrate for lipogenesis in most mammals?

  • Insulin
  • Acetate
  • Palmitate
  • Glucose (correct)
  • Which molecule is the main fuel molecule produced by the diet in ruminants for lipogenesis?

  • Insulin
  • Palmitate
  • Glucose
  • Acetate (correct)
  • What critical diseases of the fatty acid biosynthesis pathway have not been reported in humans?

  • Type 1 diabetes mellitus
  • Insulin resistance (correct)
  • Inhibition of lipogenesis
  • Obesity
  • What is the benefit of having a high ratio of polyunsaturated fatty acids to saturated fatty acids (P:S ratio) in the diet?

    <p>Preventing coronary heart disease (C)</p> Signup and view all the answers

    Which essential fatty acids are used to form eicosanoic (C20) fatty acids that give rise to prostaglandins, thromboxanes, leukotrienes, and lipoxins?

    <p>Polyunsaturated fatty acids derived from plants (B)</p> Signup and view all the answers

    What functions do prostaglandins mediate according to the text?

    <p>Inflammation, pain, and regulating blood coagulation (D)</p> Signup and view all the answers

    What is the enzyme activity responsible for liberating the Fatty Acid Synthase complex from a free palmitate molecule?

    <p>Thioesterase (D)</p> Signup and view all the answers

    Which molecule must the free palmitate be converted to before proceeding through any other metabolic pathway?

    <p>Acyl-CoA (B)</p> Signup and view all the answers

    Which process describes the usual fate of palmitate after it is liberated from the Fatty Acid Synthase complex?

    <p>Esterification into acylglycerols (C)</p> Signup and view all the answers

    In which gland is there a specific thioesterase for acyl residues of 𝐶8, 𝐶10, or 𝐶12, found in milk lipids?

    <p>Mammary gland (A)</p> Signup and view all the answers

    Which molecule acts as a primer for the synthesis of long-chain fatty acids with an odd number of carbon atoms?

    <p>Propionyl CoA (A)</p> Signup and view all the answers

    What is the main source of NADPH for lipogenesis?

    <p>Pentose Phosphate Pathway (B)</p> Signup and view all the answers

    Which molecules act as cofactors in the biosynthesis of fatty acids?

    <p>NADPH, ATP, Mn2+, biotin, and HCO3- (C)</p> Signup and view all the answers

    What is the immediate substrate in the biosynthesis of fatty acids?

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

    Which vitamin is required by acetyl-CoA carboxylase in fatty acid synthesis?

    <p>Biotin (D)</p> Signup and view all the answers

    What is the main pathway for de novo synthesis of fatty acids?

    <p>Lipogenesis (B)</p> Signup and view all the answers

    Which substance is required in the initial reaction for the carboxylation of acetyl-CoA to malonyl-CoA?

    <p>Bicarbonate (HCO3-) (A)</p> Signup and view all the answers

    What type of properties do leukotrienes have?

    <p>Muscle contractant and chemotactic properties (C)</p> Signup and view all the answers

    What is the initial and controlling step in fatty acid synthesis?

    <p>Formation of malonyl-CoA (B)</p> Signup and view all the answers

    How does the synthase system differ in bacteria and plants compared to yeast, mammals, and birds?

    <p>Yeast, mammals, and birds have a multienzyme complex while bacteria and plants have separate enzymes. (B)</p> Signup and view all the answers

    What role does 4'-phosphopantetheine play in the fatty acid synthase complex?

    <p>Component of ACP in yeast, mammals, and birds (D)</p> Signup and view all the answers

    What is a key advantage of using a multienzyme functional unit for fatty acid synthesis?

    <p>Achieving compartmentalization without erecting permeability barriers (A)</p> Signup and view all the answers

    In mammals, how many monomers make up the fatty acid synthase complex?

    <p>Two monomers with all seven enzyme activities each (C)</p> Signup and view all the answers

    Which type of organism uses acyl carrier protein (ACP) in the fatty acid synthase system?

    <p>Yeast (B)</p> Signup and view all the answers

    Which metabolic pathway is the chief source of hydrogen required for the reductive synthesis of fatty acids?

    <p>Pentose phosphate pathway (A)</p> Signup and view all the answers

    Which tissues possess an active pentose phosphate pathway and are specialized in active lipogenesis?

    <p>Adipose tissue (A)</p> Signup and view all the answers

    What is the main source of NADPH required for lipogenesis?

    <p>Malate to pyruvate conversion (D)</p> Signup and view all the answers

    Where is acetyl-CoA mainly formed from glucose for fatty acid synthesis?

    <p>Mitochondria (D)</p> Signup and view all the answers

    Which reaction converts malate to pyruvate and is involved in generating NADPH for lipogenesis?

    <p>Malic enzyme reaction (C)</p> Signup and view all the answers

    Why does acetyl-CoA not diffuse readily into the extramitochondrial cytosol?

    <p>Principal site of fatty acid synthesis is outside mitochondria (A)</p> Signup and view all the answers

    What is the fate of citrate in the extramitochondrial compartment?

    <p>It is converted to acetyl-CoA and oxaloacetate (D)</p> Signup and view all the answers

    What enzyme catalyzes the cleavage of citrate into acetyl-CoA and oxaloacetate?

    <p>ATP-citratlyase (C)</p> Signup and view all the answers

    How is NADPH generated from oxaloacetate via malate?

    <p>By malate dehydrogenase (A)</p> Signup and view all the answers

    What is the function of the malic enzyme in the context of lipogenesis?

    <p>Generating NADPH from malic acid (C)</p> Signup and view all the answers

    How can reducing equivalents be transferred from extramitochondrial NADH to NADP?

    <p>Via malate formation from citrate (B)</p> Signup and view all the answers

    In what form does malate need to be for the citrate transporter to exchange it with citrate in the mitochondrion?

    <p>Oxaloacetate (C)</p> Signup and view all the answers

    What is the primary role of acetyl-CoA in fatty acid biosynthesis?

    <p>Formation of malonyl-CoA (D)</p> Signup and view all the answers

    How is pyruvate used in the context of fatty acid synthesis?

    <p>To regenerate acetyl-CoA in the mitochondrion (C)</p> Signup and view all the answers

    Which molecule is required for the exchange of citrate with malate in the mitochondrion?

    <p>Oxaloacetate (C)</p> Signup and view all the answers

    What is the significance of ATP in the cleavage of citrate into acetyl-CoA and oxaloacetate?

    <p>Provides energy for the reaction (B)</p> Signup and view all the answers

    What is the fate of citrate after it is translocated into the extramitochondrial compartment?

    <p>It is converted back to acetyl-CoA by ATP-citratlyase (A)</p> Signup and view all the answers

    Which enzyme catalyzes the cleavage of citrate into acetyl-CoA and oxaloacetate?

    <p>ATP-citratlyase (C)</p> Signup and view all the answers

    What is the primary building block used in the biosynthesis of fatty acids?

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

    Which molecule is responsible for transferring reducing equivalents from extramitochondrial NADH to NADP?

    <p>Malate (B)</p> Signup and view all the answers

    What is the final product generated by malic enzyme from oxaloacetate?

    <p>NADPH (A)</p> Signup and view all the answers

    Which enzyme converts malate to pyruvate for generating NADPH in lipogenesis?

    <p>Malic enzyme (B)</p> Signup and view all the answers

    Where does the tricarboxylate transporter translocate citrate into?

    <p>Extramitochondrial compartment (C)</p> Signup and view all the answers

    In which state does ATP-citratlyase exhibit increased activity?

    <p>'Well-fed' state (C)</p> Signup and view all the answers

    What is the role of pyruvate in relation to acetyl-CoA in lipogenesis?

    <p>Transports acetyl-CoA into mitochondria for synthesis (B)</p> Signup and view all the answers

    What is the function of the malic enzyme in lipogenesis?

    <p>Generates NADPH from oxaloacetate. (B)</p> Signup and view all the answers

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