Biochemistry: Fatty Acid Synthesis and Lipoproteins
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Questions and Answers

What is the primary synthesis location of Apolipoprotein A-V?

  • Adipose tissue
  • Liver (correct)
  • Intestine
  • Muscle
  • Which apolipoprotein is specifically associated with the structural composition of chylomicrons?

  • Apo A-IV
  • Apo B-48 (correct)
  • Apo C-II
  • Apo E
  • Apolipoproteins C-II and C-III have opposing roles. What function does Apo C-II serve?

  • Enhances receptor interaction of triglyceride rich lipoproteins
  • Increases atherosclerosis risk
  • Stimulates triglyceride hydrolysis (correct)
  • Inhibits lipoprotein lipase activity
  • What is a key risk factor associated with high levels of Apo B-100?

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

    Which apolipoprotein serves as a co-factor for lipoprotein lipase (LPL)?

    <p>Apo C-II</p> Signup and view all the answers

    Which apolipoprotein is known to inhibit fibrinolysis?

    <p>Apo (a)</p> Signup and view all the answers

    Apolipoprotein E primarily aids in the metabolism of which lipoproteins?

    <p>Chylomicrons and chylomicron remnants</p> Signup and view all the answers

    What role does Apo C-III play in lipid metabolism?

    <p>Inhibits lipoprotein lipase activity</p> Signup and view all the answers

    Who studied the process of fatty acid synthesis and won the Nobel prize in 1964?

    <p>Feodor Lynen</p> Signup and view all the answers

    Where does the de novo synthesis of fatty acids primarily occur?

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

    Which fatty acid is primarily synthesized through the de novo pathway?

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

    Which of the following is included in the net reaction for the de novo synthesis of palmitate?

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

    What is the primary function of chylomicrons in lipid metabolism?

    <p>Transport dietary triglycerides and cholesterol to peripheral tissues</p> Signup and view all the answers

    Which class of lipoproteins is characterized as the largest and least dense?

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

    How are plasma lipoproteins primarily classified?

    <p>By size, lipid composition, and apolipoproteins</p> Signup and view all the answers

    What happens to the size of chylomicrons in the fasting state compared to after a high-fat meal?

    <p>They are smaller</p> Signup and view all the answers

    What happens to chylomicrons after triglyceride is removed by lipoprotein lipase?

    <p>They form chylomicron remnants enriched in cholesterol.</p> Signup and view all the answers

    Which lipoprotein is primarily responsible for carrying the majority of cholesterol in circulation?

    <p>Low density lipoprotein (LDL)</p> Signup and view all the answers

    Which type of apolipoprotein accounts for approximately 70% of HDL protein?

    <p>Apolipoprotein A-I</p> Signup and view all the answers

    What is one of the significant roles of HDL particles in the body?

    <p>They facilitate reverse cholesterol transport to the liver.</p> Signup and view all the answers

    How do IDL particles differ from VLDL particles?

    <p>IDL particles are formed after triglyceride removal from VLDL.</p> Signup and view all the answers

    What is the relationship between apolipoprotein A-II and cardiovascular disease (CVD)?

    <p>Apo A-II is an indicator for increased risk of CVD.</p> Signup and view all the answers

    Which lipoprotein type is primarily triglyceride-rich and produced by the liver?

    <p>Very low density lipoprotein (VLDL)</p> Signup and view all the answers

    What is one of the functions of apolipoproteins?

    <p>To guide the formation of lipoproteins.</p> Signup and view all the answers

    Study Notes

    De Novo Synthesis of Fatty Acids

    • Fatty acid synthesis was studied by Feodor Lynen, who received the Nobel Prize in 1964.
    • The pathway is also referred to as Lynen's spiral.
    • Fatty acids are primarily synthesized in the cytoplasm.
    • The major fatty acid synthesized de novo is palmitic acid (16 carbons).
    • This process occurs in liver, adipose tissue, kidney, brain, and mammary glands.
    • The net reaction of de novo fatty acid synthesis can be summarized as: 1Acetyl CoA + 7Malonyl CoA + 14NADPH + 14H → 1Palmitate + 7CO2 + 14NADP + 8CoA + 6H₂O.
    • Note: fatty acid synthesis is not an exact reversal of beta-oxidation.

    Lipoproteins

    • Lipoproteins are complex particles composed of a hydrophobic core of non-polar lipids (primarily triglycerides and cholesterol esters) surrounded by a hydrophilic membrane (phospholipids, free cholesterol, and apolipoproteins).
    • Plasma lipoproteins are classified into seven types based on size, lipid composition, and apolipoproteins.

    Classes of Lipoproteins

    • Chylomicrons: Largest and least dense lipoproteins, transporting dietary triglycerides and cholesterol. Size varies with fat intake. Small particles in the fasting state.
    • Chylomicron remnants: Smaller particles formed when peripheral tissues remove triglycerides from chylomicrons via lipoprotein lipase. Enriched in cholesterol, pro-atherogenic.
    • Very Low-Density Lipoproteins (VLDL): Liver-produced; rich in triglycerides. Large particles when triglyceride production is high, smaller than chylomicrons.
    • Intermediate-Density Lipoproteins (IDL): formed from VLDL; enriched in cholesterol; pro-atherogenic.
    • Low-Density Lipoproteins (LDL): Formed from VLDL and IDL; very rich in cholesterol; major cholesterol carrier in circulation.
    • High-Density Lipoproteins (HDL): Play a role in reverse cholesterol transport (from peripheral tissues to liver). Anti-oxidant, anti-inflammatory, anti-thrombotic, and anti-apoptotic properties. Associated with decreased risk of atherosclerosis; enriched in cholesterol and phospholipids.
    • Lipoprotein (a) (Lp(a)): Homolog of plasminogen; high levels are associated with an increased risk of atherosclerosis.

    Apolipoproteins

    • Apolipoproteins have four major functions: structural role, ligands for receptors, regulating lipoprotein formation, and activating/inhibiting enzymes involved in lipoprotein metabolism.
    • Various types of apolipoproteins exist: A-I, A-II, A-IV, A-V, B-48, B-100, C (C-I, C-II, C-III), and E. Each has specific roles in lipoprotein metabolism.
    • Apo A-I is the major structural protein in HDL, associated with a decreased risk of atherosclerosis.
    • Apo B-100 is a major structural component of VLDL, IDL, and LDL, associated with increased risk of atherosclerosis.
    • Apo C-II acts as a co-factor for lipoprotein lipase (LPL), stimulating triglyceride hydrolysis.
    • Apo C-III inhibits LPL and interactions of triglyceride-rich lipoproteins with their receptors.
    • Apo E associated with chylomicrons, chylomicron remnants, VLDL, IDL, and HDL.
    • Apo (a) is a homolog of plasminogen and high levels are associated with increased risk of atherosclerosis.

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    Description

    This quiz explores two key concepts in biochemistry: de novo synthesis of fatty acids and the structure of lipoproteins. Learn about the pathway described by Nobel Laureate Feodor Lynen, along with the classification and composition of various lipoproteins. Test your knowledge with this comprehensive overview.

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