Biochemistry LE 3: Cholesterol and Lipoprotein Pathway
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Questions and Answers

What happens to acetyl-CoA when NADH is high?

  • It is converted into ketone bodies (correct)
  • It is transformed into pyruvate
  • It is converted into lactate
  • It enters the TCA cycle

    • What is the impact of high NADH on gluconeogenesis?

  • It increases oxaloacetate levels
  • It decreases oxaloacetate levels
  • It converts oxaloacetate into malate (correct)
  • It has no effect on oxaloacetate levels

    • What is the consequence of high NADH on pyruvate?

  • It is converted into oxaloacetate
  • It is converted into acetyl-CoA
  • It is converted into lactate (correct)
  • It is converted into malate

    • What is the clinical consequence of lactate accumulation?

    <p>Impaired uric acid excretion</p> Signup and view all the answers

    What is the role of PEPCK in gluconeogenesis?

    <p>It converts oxaloacetate to PEP</p> Signup and view all the answers

    What is the consequence of high NADH on glucose oxidation?

    <p>It decreases glucose oxidation</p> Signup and view all the answers

    What is the effect of chronic alcoholism on glucose metabolism?

    <p>It induces hyperglycemia</p> Signup and view all the answers

    What is the consequence of high NADH on malate?

    <p>It increases malate levels</p> Signup and view all the answers

    What is the role of GA3P DH in gluconeogenesis?

    <p>It requires NAD+ as a cofactor</p> Signup and view all the answers

    Where does the MEOS produce acetaldehyde and NADP+?

    <p>Endoplasmic reticulum</p> Signup and view all the answers

    What is the committed enzyme of cholesterol de novo synthesis?

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

    What is the source of Acetyl CoA in cholesterol synthesis?

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

    How many NADPH molecules are required for cholesterol synthesis?

    <p>16</p> Signup and view all the answers

    In which state does endogenous de novo synthesis of cholesterol occur?

    <p>Fed state</p> Signup and view all the answers

    What is the source of exogenous cholesterol in the diet?

    <p>Animal source</p> Signup and view all the answers

    How many stages are involved in cholesterol biosynthesis?

    <p>5</p> Signup and view all the answers

    What is the product of the condensation of six isoprene units?

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

    What is the final product of cholesterol biosynthesis?

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

    What happens to SREBP-1 when there is an abundance of cholesterol?

    <p>It forms a complex with SCAP and Insig-1, becoming biologically inactive</p> Signup and view all the answers

    What is the result of step 8 in cholesterol formation?

    <p>Formation of 27-carbon cholesterol</p> Signup and view all the answers

    What happens to SREBP-1 when there is a depletion of cholesterol?

    <p>It translocates into the golgi apparatus and becomes biologically active</p> Signup and view all the answers

    What is the end product of step 12 in cholesterol formation?

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

    What is the function of Insig-1 in the regulation of SREBP-1?

    <p>It inhibits the activity of SREBP-1</p> Signup and view all the answers

    What is the intermediate formed in step 9 of cholesterol formation?

    <p>1,4-Demethyl lanosterol</p> Signup and view all the answers

    What is the function of SREBP-1 in the nucleus?

    <p>It enhances gene transcription</p> Signup and view all the answers

    What is the intermediate formed in step 10 of cholesterol formation?

    <p>7,24-Cholestadienol</p> Signup and view all the answers

    What is the role of the golgi apparatus in SREBP-1 activation?

    <p>It activates SREBP-1</p> Signup and view all the answers

    What is the product of the decarboxylation of lanosterol?

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

    What is the substrate for the isomerization reaction in Step 10?

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

    What is the result of high sterol molecules in the ER?

    <p>The complex of SREBP 1 and SCAP remains in the ER membrane</p> Signup and view all the answers

    What happens to the complex of SREBP 1 and SCAP when sterol molecules are low in the ER?

    <p>It translocates to the Golgi complex</p> Signup and view all the answers

    What is the role of Insig in the regulation of SREBP 1?

    <p>It escorts SREBP 1 to the Golgi complex</p> Signup and view all the answers

    What is the primary function of LPL?

    <p>To extract free fatty acids or TAGs from VLDL</p> Signup and view all the answers

    What is the result of SREBP 1 translocating to the nucleus?

    <p>It enhances gene expression of HMGR</p> Signup and view all the answers

    What is the fate of excess LDL?

    <p>It gets oxidized by macrophages, forming foam cells</p> Signup and view all the answers

    What is the function of the DNA binding domain of SREBP 1?

    <p>It enhances gene transcription</p> Signup and view all the answers

    What is the role of the liver in the transportation of TAGs?

    <p>It transports TAGs out of the liver by VLDL</p> Signup and view all the answers

    What is the purpose of the regulation of HMG-CoA reductase?

    <p>To regulate cholesterol levels in the cell</p> Signup and view all the answers

    What is the result of low sterol molecules in the ER?

    <p>The complex of SREBP 1 and SCAP translocates to the Golgi complex</p> Signup and view all the answers

    What is the function of HTGL?

    <p>To hydrolyze IDL into LDL</p> Signup and view all the answers

    What is the location of the carboxy terminal domain of the LDL receptor?

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

    What is the function of the O-linked oligosaccharide domain of the LDL receptor?

    <p>To extend the receptor away from the membrane</p> Signup and view all the answers

    What is the function of the LDL-binding region of the LDL receptor?

    <p>To bind LDL</p> Signup and view all the answers

    What is unique about the structure of the LDL receptor?

    <p>It is composed of multiple domains</p> Signup and view all the answers

    What is the significance of the cysteine sequences joined by disulfide bonds in the LDL receptor?

    <p>They contribute to the structural stability of the receptor</p> Signup and view all the answers

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