Lipids 3
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Questions and Answers

Where does de novo synthesis of fatty acids mainly occur?

  • Kidneys
  • Adipose tissue cells (correct)
  • Liver cells
  • Mammary glands

    • What is the main source of mitochondrial Acetyl CoA production?

  • Oxidation of pyruvate (correct)
  • Oxidation of citrate
  • Carboxylation of malonyl CoA
  • Condensation of acetyl CoA with oxaloacetate

    • In the process of ACoA carboxylation to Malonyl CoA, which molecule is required for the carboxylation process?

  • Riboflavin
  • Biotin (correct)
  • Niacin
  • Ascorbic Acid

    • What substrates are used in de novo fatty acid synthesis?

    <p>Excess carbohydrates and proteins from the diet</p> Signup and view all the answers

    Which enzyme is key in de novo fatty acid synthesis?

    <p>Acetyl Coenzyme A</p> Signup and view all the answers

    What is the enzyme responsible for catalyzing the carboxylation of ACoA to Malonyl CoA?

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

    What is the primary end product of de novo fatty acid synthesis?

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

    Which molecule allosterically activates Acetyl CoA carboxylase (ACC)?

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

    What stimulates ACC synthesis hormonally?

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

    In which organelle does the elongation of fatty acids occur?

    <p>Smooth endoplasmic reticulum</p> Signup and view all the answers

    What type of fatty acids can be produced by adding cis double bonds in desaturation?

    <p>Polyunsaturated fatty acids</p> Signup and view all the answers

    In the cytosol, how is citrate converted back to Oxaloacetate (OAA) and Acetyl CoA?

    <p>By ATP citrate lyase activity</p> Signup and view all the answers

    What is the end product of fatty acid synthesis in eukaryotes?

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

    Where do the carbons used in fatty acid synthesis come from?

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

    What is the role of the Pentose Phosphate Pathway in fatty acid synthesis?

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

    How does the presence of unsaturated fatty acids affect the melting temperature of lipids?

    <p>Decreases the melting temperature</p> Signup and view all the answers

    Which type of fatty acids are generally found at position C-1 in triacylglycerols?

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

    What is the caloric value per unit mass of triacylglycerols compared to carbohydrates and proteins?

    <p>$9$ kCal/gm for TG, about $4$ kCal/gm for carbohydrate and proteins</p> Signup and view all the answers

    Which tissue has the ability to use ketone bodies at high concentrations?

    <p>Brain cells</p> Signup and view all the answers

    What is the main purpose of ketone bodies during fasting or prolonged exercise?

    <p>Provide an alternative energy source</p> Signup and view all the answers

    What metabolic process stimulates the production of ketone bodies due to the excess of Acetyl CoA?

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

    Which of the following is NOT a function of ketone bodies in the body?

    <p>Enhancing insulin secretion</p> Signup and view all the answers

    What triggers the increased production of ketone bodies in the liver during fasting?

    <p>Mobilization of fatty acids from adipose tissue</p> Signup and view all the answers

    How are ketone bodies utilized by peripheral tissues?

    <p>Oxidized to produce energy</p> Signup and view all the answers

    What is the major pathway for fatty acid catabolism?

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

    Which enzyme is responsible for mobilizing fat through lipolysis?

    <p>Hormone-Sensitive-Lipase (HSL)</p> Signup and view all the answers

    What inhibits the carnitine shuttle (CPT1) in fatty acid beta-oxidation?

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

    What is the role of the carnitine shuttle in fatty acid beta-oxidation?

    <p>To transport fatty-acyl-CoA into the mitochondria</p> Signup and view all the answers

    Which compound is synthesized from lysine and methionine and helps transport fatty acids into mitochondria?

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

    What does the first cycle of beta-oxidation produce?

    <p>1 Acetyl-CoA + 1 NADH + 1 FADH2</p> Signup and view all the answers

    What is the main function of ATP citrate lyase in fatty acid synthesis?

    <p>Facilitates the conversion of citrate to oxaloacetate and Acetyl CoA</p> Signup and view all the answers

    What is the effect of palmitoyl CoA on acetyl CoA carboxylase (ACC)?

    <p>It inhibits ACC</p> Signup and view all the answers

    Which molecule serves as a negative feedback regulator of acetyl CoA carboxylase (ACC) activity?

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

    What stimulates acetyl CoA carboxylase (ACC) synthesis hormonally?

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

    In which pathway is acetyl CoA carboxylase (ACC) considered the rate-limiting step?

    <p>De Novo synthesis of fatty acids</p> Signup and view all the answers

    What is the role of citrate in stimulating ATP citrate lyase activity?

    <p>Activates ATP citrate lyase by allosteric regulation</p> Signup and view all the answers

    What are the final products after the full oxidation of 1 palmitoyl CoA?

    <p>ATP, CO2, H2O</p> Signup and view all the answers

    What is the alternative fuel produced by the liver mitochondria from fatty acid oxidation?

    <p>Ketone bodies</p> Signup and view all the answers

    Where are acetoacetate and ß-hydroxybutyrate transported for utilization in peripheral tissues?

    <p>Blood plasma</p> Signup and view all the answers

    What can acetoacetate and ß-hydroxybutyrate be converted back into within peripheral tissue cells?

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

    What happens to acetone produced during ketone body metabolism?

    <p>Excreted through breath and urine</p> Signup and view all the answers

    What is the end product of fatty acid synthesis catalyzed by fatty acid synthase in eukaryotes?

    <p>Palmitate (16:0)</p> Signup and view all the answers

    What is the role of the Pentose Phosphate Pathway in fatty acid synthesis?

    <p>Provides reductant NADH</p> Signup and view all the answers

    What is the caloric value per unit mass of triacylglycerols compared to carbohydrates and proteins?

    <p>9 kCal/gm for TG, about 4 kCal/gm for carbohydrate and protein</p> Signup and view all the answers

    What type of fatty acids are generally NOT found at position C-2 in triacylglycerols?

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

    What decreases the melting temperature of lipids?

    <p>Presence of unsaturated fatty acids</p> Signup and view all the answers

    How are newly synthesized fatty acids primarily stored in the body?

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

    Where does de novo fatty acid synthesis mainly occur?

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

    Which of the following tissues can synthesize fatty acids in small quantities, besides liver, mammary glands, and adipose tissue cells?

    <p>Brain cells</p> Signup and view all the answers

    What is the primary end product of de novo fatty acid synthesis?

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

    Which organelle is key for providing Acetyl Coenzyme A (ACoA) as a substrate for fatty acid synthesis?

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

    Which enzymes in the smooth endoplasmic reticulum can cause desaturation of long-chain fatty acids by adding double bonds?

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

    What is the main function of ketone bodies during fasting and prolonged exercise?

    <p>Save glucose</p> Signup and view all the answers

    Which tissue has the ability to utilize ketone bodies at high concentrations?

    <p>Cardiac muscle</p> Signup and view all the answers

    What stimulates the liver to produce high levels of ketone bodies during fasting?

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

    Which molecule is produced when 3-hydroxybutyrate is oxidized in peripheral tissues?

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

    What is the primary role of lipolysis in adipocytes?

    <p>Mobilize triglycerides</p> Signup and view all the answers

    In which condition do ketone bodies increase, leading to their elevated use as an energy source by peripheral tissues?

    <p>Diabetes mellitus</p> Signup and view all the answers

    What is the common compound that fatty acids are synthesized from and oxidized to?

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

    Where are fatty acids oxidized and synthesized within the cell?

    <p>Both in the mitochondria</p> Signup and view all the answers

    Under what conditions do physiological factors largely inhibit fatty acid oxidation?

    <p>High NADH/NAD+ ratio</p> Signup and view all the answers

    Which process prevents 'futile cycling' by largely inhibiting fatty acid oxidation?

    <p>Fatty acid synthesis</p> Signup and view all the answers

    What is the primary compound that connects the pathway for mobilization of fats with beta-oxidation?

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

    What are the final products after the full oxidation of 1 palmitoyl CoA?

    <p>ATP, CO2, H2O</p> Signup and view all the answers

    What are the primary ketone bodies formed in the adult liver mitochondria from fatty acid oxidation?

    <p>Acetoacetate, ß-hydroxybutyrate, Acetone</p> Signup and view all the answers

    What can happen to acetone produced during ketone body metabolism?

    <p>It is exhaled through the lungs</p> Signup and view all the answers

    Which tissues can receive transported ketone bodies for utilization?

    <p>Muscle and Brain</p> Signup and view all the answers

    What is the alternative fuel that cells can derive from ACoA in peripheral tissues?

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

    What is the primary role of Hormone-Sensitive-Lipase (HSL) in the context of fat mobilization?

    <p>Promoting lipolysis</p> Signup and view all the answers

    Which compound is required for the transport of fatty-acyl-CoA into the mitochondria for beta-oxidation?

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

    What can cause decreased ability of tissues to use long-chain fatty acids as fuel?

    <p>Carnitine deficiencies</p> Signup and view all the answers

    Which process can inhibit the transfer of newly synthesized fatty acids into the mitochondria for degradation?

    <p>Fatty acid synthesis</p> Signup and view all the answers

    What is the rate-limiting step for transporting fatty-acyl-CoA into the mitochondria?

    <p>Carnitine shuttle activity</p> Signup and view all the answers

    What is the main product generated in each cycle of fatty acid beta-oxidation?

    <p>$1$ acetyl-CoA + $1$ NADH + $1$ FADH2</p> Signup and view all the answers

    What is the primary role of acetone in ketotic patients?

    <p>Causing a fruity smell on breath and urine</p> Signup and view all the answers

    Why do ketone bodies save glucose during fasting?

    <p>By providing an alternative energy source for tissues</p> Signup and view all the answers

    Where are ketone bodies primarily produced?

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

    Why does the liver increase ketone body production during fasting?

    <p>To meet the energy demands of peripheral tissues</p> Signup and view all the answers

    What stimulates the production of ketone bodies due to excess Acetyl CoA?

    <p>Exceeding oxidative capacity of the liver</p> Signup and view all the answers

    How are ketone bodies utilized by peripheral tissues?

    <p>Supplying an energy source proportional to their blood concentration</p> Signup and view all the answers

    What is the main role of ATP citrate lyase in the context of fatty acid synthesis?

    <p>Production of citrate from ACoA and oxaloacetate</p> Signup and view all the answers

    Which molecule allosterically activates acetyl CoA carboxylase (ACC) in fatty acid synthesis?

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

    Which factor negatively regulates acetyl CoA carboxylase (ACC) activity in fatty acid synthesis?

    <p>Decreased citrate concentration</p> Signup and view all the answers

    What is the primary requirement for the carboxylation of Acetyl CoA to Malony CoA in fatty acid synthesis?

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

    What stimulates acetyl CoA carboxylase (ACC) synthesis in the context of fatty acid synthesis?

    <p>High-carbohydrate diet</p> Signup and view all the answers

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