Insulin and Fatty Acid Synthesis Quiz
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Insulin and Fatty Acid Synthesis Quiz

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Questions and Answers

What role does acetyl-CoA carboxylase (ACC) play in fatty acid synthesis?

  • It is the rate limiting step in fatty acid synthesis. (correct)
  • It inhibits ATP production.
  • It activates fatty acid breakdown.
  • It promotes glucose metabolism.

    • How does a high concentration of AMP affect acetyl-CoA carboxylase (ACC)?

  • It activates ACC directly.
  • It increases the synthesis of fatty acids.
  • It has no effect on ACC.
  • It inhibits ACC through AMPK activation. (correct)

    • What occurs when the ADP:ATP ratio increases?

  • Energy levels in the cell improve.
  • Adenylate kinase reaction is displaced to produce ATP. (correct)
  • AMPK is inactivated.
  • AMP concentration decreases.

    • What is primarily produced from acetyl-CoA and malonyl-CoA in fatty acid synthesis?

    <p>Palmitic acid (C16)</p> Signup and view all the answers

    What happens to AMPK in the presence of insulin?

    <p>AMPK is inhibited.</p> Signup and view all the answers

    What does a high carbohydrate meal stimulate in the body?

    <p>Insulin secretion and fatty acid synthesis.</p> Signup and view all the answers

    How is ATP mainly generated in animal cells?

    <p>Through mitochondrial ATP synthase.</p> Signup and view all the answers

    What is the consequence of not maintaining a balance between ATP generation and consumption?

    <p>Cellular energy depletion.</p> Signup and view all the answers

    Where does catabolism of fatty acids primarily occur?

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

    Which enzyme is the rate limiting step in fatty acid synthesis?

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

    What role does insulin play in fatty acid synthesis?

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

    Where are the enzymes involved in triglyceride biosynthesis primarily found?

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

    What is the primary source of acetyl-CoA in the cytoplasm for fatty acid synthesis?

    <p>Citrate-malate shuttle from mitochondria</p> Signup and view all the answers

    Which organelles are crucial for lipid storage?

    <p>Lipid droplets</p> Signup and view all the answers

    What process couples deacetylation in the mitochondria with acetylation in the cytosol?

    <p>Citrate-malate shuttle</p> Signup and view all the answers

    What promotes the production of citrate and acetyl-CoA in the cytosol?

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

    Which enzyme is primarily responsible for the final step in triglyceride synthesis in the endoplasmic reticulum?

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

    What type of lipids are predominantly synthesized in the endoplasmic reticulum in eukaryotic cells?

    <p>Neutral lipids</p> Signup and view all the answers

    Which pathway is considered the primary pathway for triglyceride synthesis?

    <p>De novo glycerolipid synthesis pathway</p> Signup and view all the answers

    What is the function of ACAT enzymes found in the endoplasmic reticulum?

    <p>Synthesize cholesterol esters</p> Signup and view all the answers

    In which type of cells is the monoacylglycerol pathway particularly important for triglyceride synthesis?

    <p>Intestinal enterocytes</p> Signup and view all the answers

    What role do MGAT enzymes play in triglyceride synthesis?

    <p>Recycling monoacylglycerols back to TGs</p> Signup and view all the answers

    Which of the following statements about triglycerides (TGs) is correct?

    <p>The biochemical reactions for TG synthesis were elucidated in the 1960s.</p> Signup and view all the answers

    What happens to the lipids stored in lipid droplets?

    <p>They can be stored for long-term use.</p> Signup and view all the answers

    What structural characteristic differentiates microvesicular steatosis from macrovesicular steatosis in hepatocytes?

    <p>Presence of multiple small lipid droplets</p> Signup and view all the answers

    Which hormone is primarily responsible for the growth of glycogen granules in the fed state?

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

    How does glucagon affect glycogen granules during fasting?

    <p>Causes them to shrink</p> Signup and view all the answers

    What is the primary function of glycogen in muscle cells?

    <p>Source of energy for ATP synthesis</p> Signup and view all the answers

    What role does insulin play in glucose homeostasis?

    <p>Inhibits gluconeogenesis</p> Signup and view all the answers

    What happens to glycogen in the liver during prolonged fasting?

    <p>It is utilized as an energy source</p> Signup and view all the answers

    What would likely occur if glucose-6-phosphatase were deleted?

    <p>Inability to release glucose into the bloodstream</p> Signup and view all the answers

    Which cellular structure is typically associated with glycogen granules?

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

    Study Notes

    Insulin and Fatty Acid Synthesis

    • High carbohydrate meals stimulate insulin secretion
    • Insulin activates fatty acid synthesis
    • High carbohydrates lead to increased production of citrate and acetyl-CoA in the cytosol
    • Acetyl-CoA carboxylase (ACC) is the rate-limiting step in fatty acid synthesis
    • ACC is inhibited by AMP-activated protein kinase (AMPK)
    • AMPK is activated when the AMP/ADP ratio is high.
    • AMP/ADP ratio increases when glucose levels are high
    • AMPK phosphorylates ACC, inhibiting its activity, therefore decreasing fatty acid synthesis
    • AMPK is inactive in the presence of insulin

    Fatty Acid Synthesis: Palmitic Acid Synthesis

    • Fatty acid synthesis starts with the formation of palmitic acid (C16) from acetyl-CoA and malonyl-CoA
    • Malonyl-CoA is a 3-carbon molecule formed from acetyl-CoA
    • Fatty acid synthesis occurs in the cytoplasm.
    • Fatty acid synthase, a multi-enzyme complex, is found in the cytoplasm
    • Acetyl-CoA for fatty acid synthesis is derived from the mitochondrial acetyl-CoA through the citrate-malate shuttle

    Triglyceride Biosynthesis

    • Acyl-CoA can include fatty acids like palmitate, forming palmitoyl-CoA
    • Triglyceride biosynthesis occurs in the smooth endoplasmic reticulum (ER)
    • Enzymes involved in triglyceride biosynthesis are located in the ER
    • Lipid droplets are formed by budding from the ER.
    • Lipid droplets store lipids long-term.
    • DGAT enzymes catalyze the terminal step in triglyceride synthesis.
    • ACAT enzymes synthesize cholesterol esters in the ER.
    • Cholesterol esters can be stored in lipid droplets.

    Lipid Droplets

    • Lipid droplets are organelles for lipid storage
    • Lipids stored include cholesterol esters and triglycerides.

    Glycerophospholipid and Triglyceride Synthesis

    • Glycerophospholipids and triglycerides are classified as neutral lipids (no charge, insoluble in water)
    • Glycerophospholipids and triglycerides are synthesized in the ER
    • The Kennedy pathway is the primary pathway for triglyceride synthesis
    • The Kennedy pathway utilizes glycerolphosphate and fatty acyl-CoA to produce glycerolipids
    • A second pathway for triglyceride synthesis, the monoacylglycerol pathway, exists in some cells types
    • The monoacylglycerol pathway recycles mono- and diarylglycerols back into triglycerides

    Liver Histology

    • Liver steatosis refers to abnormal lipid accumulation in hepatocytes.
    • Microvesicular steatosis is characterized by small lipid droplets and preserved cell structure.
    • Macrovesicular steatosis exhibits large lipid droplets that displace the nucleus.

    Dietary Carbohydrates and VLDL Production

    • Increased dietary carbohydrate intake leads to increased production of very-low-density lipoprotein (VLDL)
    • VLDL is a plasma triglyceride

    Glucose Homeostasis

    • Glucose homeostasis is maintained by insulin and glucagon.
    • Insulin and glucagon are hormones.

    Glycogen Granules

    • Glycogen is stored as granules in cells
    • Glycogen granules increase in size during the fed state, regulated by insulin
    • Glycogen granules decrease in size during the fasting state, regulated by glucagon.
    • Liver glycogen is a glucose source for gluconeogenesis
    • Muscle glycogen provides energy for ATP synthesis.

    Glucose-6-Phosphatase Deficiency

    • Glucose-6-phosphatase is an enzyme involved in glucose metabolism
    • Deletion of glucose-6-phosphatase would lead to a clinical manifestation known as von Gierke disease.
    • Clinical features of von Gierke disease include hypoglycemia, hepatomegaly, and lactic acidosis.

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    Related Documents

    Week 4 Lecture 6 PDF

    Description

    This quiz covers the biochemical pathways linking insulin secretion to fatty acid synthesis. It focuses on the role of key metabolites like acetyl-CoA and malonyl-CoA, as well as the regulation by AMP-activated protein kinase. Test your understanding of these complex interactions in lipid metabolism.

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