Lipoprotein Metabolism and Lipid Absorption
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Questions and Answers

What is the primary defect in familial type III hyperlipoproteinemia?

  • Increased catabolism of VLDL
  • Excessive production of HDL
  • Deficiency in remnant clearance by the liver (correct)
  • High levels of LDL synthesis

    • Which of the following is a characteristic of familial hypertriacylglycerolemia?

  • Decreased glucose intolerance
  • Subnormal HDL cholesterol levels (correct)
  • Low triglyceride levels
  • High LDL cholesterol levels

    • What condition can result from a deficiency of hepatic lipase?

  • Hypercholesterolemia without xanthomas
  • Elevation of triacylglycerol-rich lipoproteins (correct)
  • Increased HDL clearance
  • Reduction in VLDL levels

    • What are the major components that characterize atherosclerosis?

    <p>Lipids, cholesterol, calcium, and cellular debris</p> Signup and view all the answers

    Which serum lipid level is considered desirable for HDL cholesterol in females?

    <p>60 mg/dl</p> Signup and view all the answers

    What are primary disorders of plasma lipoproteins primarily caused by?

    <p>Genetic mutations affecting lipoprotein metabolism</p> Signup and view all the answers

    Which of the following is NOT considered a secondary disorder that affects lipoprotein levels?

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

    Which condition is characterized by a defect in the loading of apo B, leading to no formation of certain lipoproteins?

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

    Which of the following disorders is most likely to result in elevated LDL levels?

    <p>Familial hypercholesterolemia</p> Signup and view all the answers

    What is a common characteristic of Familial lipoprotein lipase deficiency (Type I)?

    <p>Slow clearance of chylomicrons and VLDL</p> Signup and view all the answers

    Which of the following conditions is associated with low HDL levels?

    <p>Tangier disease</p> Signup and view all the answers

    What is a significant risk factor for atherosclerosis related to hyperlipoproteinemia?

    <p>Defective LDL receptors</p> Signup and view all the answers

    Which disorder involves a deficiency of apo C-II, resulting in hypertriacylglycerolemia?

    <p>Familial lipoprotein lipase deficiency</p> Signup and view all the answers

    What role does HDL primarily play in cholesterol metabolism?

    <p>Removes excess cholesterol from tissues</p> Signup and view all the answers

    Which apolipoproteins are synthesized in the liver and transferred to HDL?

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

    What condition is directly indicated by the defective receptor in familial hypercholesterolemia?

    <p>Decreased LDL clearance</p> Signup and view all the answers

    What is the primary function of VLDL in the body?

    <p>Transport endogenous lipids</p> Signup and view all the answers

    How does HDL prevent the internalization of LDL cholesterol in arterial walls?

    <p>By competing for binding sites with apo E</p> Signup and view all the answers

    Which statement about hyperlipoproteinemia is true?

    <p>It is characterized by elevated concentrations of lipoprotein particles.</p> Signup and view all the answers

    What is a significant biochemical consequence of HDL stimulating prostacyclin synthesis?

    <p>Prevention of thrombus formation</p> Signup and view all the answers

    What is the fate of chylomicrons in the body after they transport dietary lipids?

    <p>They are taken up by peripheral tissues.</p> Signup and view all the answers

    What process allows chylomicrons to enter the circulation after their synthesis?

    <p>Reverse pinocytosis</p> Signup and view all the answers

    Which component is essential for the transport of dietary lipids into circulation?

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

    Where does the resynthesis of triacylglycerol (TAG) from monoglycerides and fatty acids occur?

    <p>Smooth Endoplasmic Reticulum</p> Signup and view all the answers

    What must occur for long-chain fatty acids to be absorbed by enterocytes?

    <p>They must form mixed micelles with bile salts.</p> Signup and view all the answers

    What is the primary function of apolipoprotein B in lipoproteins?

    <p>Serve as a structural component</p> Signup and view all the answers

    Which disease is associated with a lack of lipoproteins containing apo B?

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

    What is formed when long-chain fatty acids are esterified in the mucosal cells?

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

    What is the role of carbohydrate residues in chylomicron synthesis?

    <p>To stabilize the lipoprotein structure</p> Signup and view all the answers

    What is the primary structural component of VLDL?

    <p>Apo B</p> Signup and view all the answers

    Which apoprotein functions as an enzyme cofactor for lipoprotein lipase?

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

    How do VLDL remnants, also known as IDL, primarily affect the levels of LDL in humans?

    <p>They are converted to LDL.</p> Signup and view all the answers

    Which apoprotein is essential for the formation of VLDL?

    <p>Apo B-100</p> Signup and view all the answers

    What primarily happens during the catabolism of chylomicrons?

    <p>Chylomicron triacylglycerol is largely hydrolyzed by lipoprotein lipase.</p> Signup and view all the answers

    What is the predominant outcome of the hydrolysis of triacylglycerol in VLDL?

    <p>Transport of fatty acids into tissues</p> Signup and view all the answers

    What is the main difference between chylomicrons and their remnants after catabolism?

    <p>Chylomicron remnants contain more cholesterol and cholesteryl esters.</p> Signup and view all the answers

    Which receptor recognizes both apo B-100 and apo E?

    <p>LDL receptor</p> Signup and view all the answers

    What role does hepatic lipase serve in the metabolism of chylomicron remnants?

    <p>It acts as a ligand and hydrolyzes remnant components.</p> Signup and view all the answers

    What common feature do chylomicrons and VLDL share during their formation?

    <p>They contain a small amount of apoproteins C and E initially.</p> Signup and view all the answers

    Which of the following lipoproteins has the lowest density?

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

    Which apoprotein acts as a ligand for HDL receptors?

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

    How are lipoproteins primarily classified based on their composition?

    <p>By their apoprotein content.</p> Signup and view all the answers

    Which apolipoprotein is primarily found in LDL?

    <p>Apo B (B-100)</p> Signup and view all the answers

    What distinguishes the classification of lipoproteins by electrophoretic pattern?

    <p>The mobility of lipoproteins based on their density.</p> Signup and view all the answers

    Which of the following statements about chylomicrons is incorrect?

    <p>Chylomicrons lose all their cholesterol during metabolism.</p> Signup and view all the answers

    Study Notes

    Lipoprotein Metabolism

    • Lipoproteins are spherical particles composed of a nonpolar core (triacylglycerol, cholesteryl ester) and a surface monolayer of amphipathic lipids (phospholipids, cholesterol, and apolipoproteins)
    • Lipoproteins are classified based on density (chylomicrons, VLDL, IDL, LDL, HDL)
    • Chylomicrons transport dietary lipids from the intestine to the rest of the body
    • VLDL transports endogenous triglycerides from the liver to the rest of the body
    • IDL is an intermediate lipoprotein formed from VLDL catabolism
    • LDL facilitates cholesterol delivery to peripheral tissues
    • HDL removes excess cholesterol from peripheral tissues and returns it to the liver

    Lipid Absorption

    • Glycerol, short-chain fatty acids (FA), and medium-chain FA are directly absorbed into the portal vein from the intestinal lumen and go to the liver.
    • Long-chain FA, free cholesterol, and β-acyl glycerol form mixed micelles with bile salts, promoting their absorption.
    • Micelles are absorbed into mucosal cells by endocytosis.
    • Lipids are then resynthesized into triacylglycerol (TAG) and packaged into chylomicrons for transport.

    Chylomicron Metabolism

    • Chylomicrons, formed by intestinal mucosal cells, transport dietary lipids into the lymphatic system and eventually the blood circulation
    • Lipoprotein lipase (LPL) on the endothelium hydrolyzes TAG in chylomicrons, releasing free fatty acids (FFAs) into tissues
    • Chylomicron remnants, containing cholesterol and cholesteryl esters, are taken up by the liver via receptor-mediated endocytosis.
    • Liver utilizes products of chylomicron remnants for the synthesis of other lipoproteins like VLDL.

    VLDL Metabolism

    • VLDL, secreted from the liver, transports endogenous TAG to peripheral tissues.
    • LPL hydrolyzes TAG in VLDL, releasing FFA into the tissues.
    • VLDL remnants are converted to IDL.

    LDL Metabolism

    • LDL, carrying cholesterol from the liver to peripheral tissues, binds to LDL receptors in cells.
    • LDL receptor-mediated endocytosis removes LDL from the blood, delivering cholesterol to the tissues.
    • In familial hypercholesterolemia, LDL receptors are deficient, resulting in elevated LDL cholesterol levels.

    HDL Metabolism

    • HDL, synthesized in the liver and intestine, mediates reverse cholesterol transport.
    • HDL picks up excess cholesterol from peripheral tissues, transferring it to the liver for excretion.
    • HDL functions as a scavenger, removing cholesterol from cells and preventing accumulation in the arteries.

    Lipoprotein Diseases

    • Hyperlipidemia (hyperlipoproteinemia) is characterized by abnormal elevations of plasma lipoprotein levels.
    • Primary disorders are genetic defects affecting lipid metabolism, while secondary disorders occur due to other underlying factors.
    • Examples of primary disorders include abetalipoproteinemia, familial hypercholesterolemia, and familial hypertriglyceridemia.

    Atherosclerosis

    • Atherosclerosis is a disease of large and medium-sized muscular arteries, characterized by a buildup of lipids, cholesterol, calcium, and cell debris within the arterial intima
    • This buildup forms atheromatous plaques, narrowing the arteries

    Blood Lipid Levels and Risk Assessment

    • Measures of total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides are used to assess risk for cardiovascular diseases.

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    Lipoprotein Metabolism Lecture Notes PDF

    Description

    This quiz explores the intricate details of lipoprotein metabolism, including the classification of lipoproteins by density and their functions in lipid transport. Additionally, it covers the mechanisms of lipid absorption in the intestines and how different fatty acids are metabolized. Test your knowledge on these essential biochemical processes.

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