Harper's Biochemistry Chapter 25 - Lipid Transport & Storage
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Questions and Answers

What is the primary function of chylomicrons in lipid transport?

  • To facilitate cholesterol conversion to bile acids
  • To absorb dietary fats and transport them to tissues (correct)
  • To transport excess glucose from the intestines
  • To deliver protein from the liver to peripheral tissues

    • Which apolipoprotein is primarily associated with very-low-density lipoproteins (VLDL)?

  • Apolipoprotein C-II
  • Apolipoprotein E
  • Apolipoprotein A-I
  • Apolipoprotein B-100 (correct)

    • What can excessive mobilization of free fatty acids (FFAs) in diabetes mellitus lead to?

  • Hypertriacylglycerolemia due to underutilization of chylomicrons (correct)
  • Enhanced lipid storage in muscle tissue
  • Increased insulin sensitivity
  • Reduced triacylglycerol levels in the bloodstream

    • How are lipoproteins made water-miscible for transport in blood plasma?

    <p>By combining with phospholipids and proteins</p> Signup and view all the answers

    What condition is commonly associated with inherited defects in lipoprotein metabolism?

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

    What impact do lipoproteins have on cholesterol transport in the body?

    <p>They facilitate the delivery of cholesterol and its esters to various tissues</p> Signup and view all the answers

    Which of the following correctly describes the relationship between VLDL and LDL in cholesterol transport?

    <p>VLDL delivers triglycerides to tissues, after which it is converted to LDL for cholesterol transport</p> Signup and view all the answers

    What mechanism contributes to fatty liver disease?

    <p>Excessive accumulation of triacylglycerol in liver tissue</p> Signup and view all the answers

    Which lipoproteins are responsible for transporting lipids from the liver to peripheral tissues?

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

    Which lipoprotein primarily transports triacylglycerol from the diet to the liver?

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

    What is the role of apolipoprotein B100 in lipoprotein function?

    <p>Facilitating the uptake of LDL by extrahepatic tissues</p> Signup and view all the answers

    Which process primarily involves the breakdown of chylomicrons into chylomicron remnants?

    <p>Lipoprotein lipase action</p> Signup and view all the answers

    Which lipoprotein is formed from the metabolism of VLDL?

    <p>Low-Density Lipoprotein (LDL)</p> Signup and view all the answers

    What is one of the main functions of High-Density Lipoprotein (HDL)?

    <p>Facilitating reverse cholesterol transport to the liver</p> Signup and view all the answers

    Which factor influences the secretion of VLDL from the liver?

    <p>Dietary composition and hormonal regulation</p> Signup and view all the answers

    What mechanism does LDL use to enter extrahepatic tissues?

    <p>ApoB100 receptor-mediated endocytosis</p> Signup and view all the answers

    What are the primary causes of nonalcoholic fatty liver disease (NAFLD)?

    <p>Obesity, insulin resistance, and metabolic syndrome</p> Signup and view all the answers

    Which apolipoprotein is particularly significant in the clearance of chylomicron remnants by the liver?

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

    What is the relationship between LDL and the development of atherosclerosis?

    <p>LDL promotes cholesterol deposition in arterial walls</p> Signup and view all the answers

    Which lipoprotein is primarily involved in reverse cholesterol transport?

    <p>High-density lipoprotein (HDL)</p> Signup and view all the answers

    In terms of lipid composition, which lipoprotein primarily contains triacylglycerol?

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

    What percentage of plasma lipids is represented by cholesterol?

    <p>14%</p> Signup and view all the answers

    Which apolipoprotein is most commonly associated with LDL lipoprotein?

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

    What is the plausible mechanism contributing to fatty liver disease in individuals with abdominal obesity?

    <p>Increased VLDL production</p> Signup and view all the answers

    Which lipoprotein is considered the final stage in the catabolism of cholesterol?

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

    What is the predominant lipid in low-density lipoproteins (LDL)?

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

    Which classification is used to categorize lipoproteins based on their electrophoretic properties?

    <p>Pre-β, β, and α classification</p> Signup and view all the answers

    Which factor is NOT commonly associated with increased mortality risk related to obesity?

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

    What is the main function of the nonpolar core in lipoproteins?

    <p>To carry triacylglycerols</p> Signup and view all the answers

    What primarily makes up the nonpolar lipid core of a lipoprotein?

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

    How does the density of a lipoprotein change with an increased lipid to protein ratio?

    <p>Density decreases</p> Signup and view all the answers

    What is the role of the polar groups in phospholipids within lipoproteins?

    <p>To face outward towards the aqueous medium</p> Signup and view all the answers

    Which type of lipoprotein is composed of nearly 70% protein?

    <p>High-Density Lipoproteins (HDL)</p> Signup and view all the answers

    In which organ are chylomicrons primarily produced?

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

    What is the primary function of apolipoproteins within lipoproteins?

    <p>To serve as signaling molecules</p> Signup and view all the answers

    Which lipoprotein type contains the smallest percentage of protein?

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

    Which lipoproteins play a crucial role in transporting cholesterol through the bloodstream?

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

    What mechanism is primarily involved in the development of fatty liver disease?

    <p>Excess fat accumulation in liver cells</p> Signup and view all the answers

    What specifically causes the amphipathic nature of phospholipids in lipoproteins?

    <p>The presence of hydrophobic tails and hydrophilic heads</p> Signup and view all the answers

    Which lipoprotein carries triacylglycerol from the liver to extrahepatic tissues?

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

    What major role does HDL play in lipid metabolism?

    <p>Reverse cholesterol transport</p> Signup and view all the answers

    Which type of lipoprotein is synthesized by intestinal cells?

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

    Which apolipoprotein is crucial for the clearance of chylomicron remnants from circulation?

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

    What is the primary function of low-density lipoprotein (LDL)?

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

    What is the result of the metabolism of VLDL by lipases?

    <p>Conversion to low-density lipoprotein (LDL)</p> Signup and view all the answers

    What health risk is associated with high levels of low-density lipoprotein (LDL)?

    <p>Increased risk of atherosclerosis</p> Signup and view all the answers

    Which factor is NOT associated with the regulation of hepatic VLDL secretion?

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

    What major lipid class does intermediate-density lipoprotein (IDL) primarily transport?

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

    What metabolic condition is linked to an excessive intake of free fatty acids (FFAs)?

    <p>Nonalcoholic fatty liver disease (NAFLD)</p> Signup and view all the answers

    What happens to the density of a lipoprotein as the lipid content increases?

    <p>It decreases as the lipid content rises.</p> Signup and view all the answers

    Which lipids primarily make up the nonpolar core of a lipoprotein?

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

    What is the orientation of the polar groups in phospholipids within lipoproteins?

    <p>They face outward towards the aqueous environment.</p> Signup and view all the answers

    What defines the protein moiety of a lipoprotein?

    <p>It is known as an apolipoprotein or apoprotein.</p> Signup and view all the answers

    Which statement best describes the contribution of lipids to lipoprotein structure?

    <p>The proportion of lipids affects both density and function.</p> Signup and view all the answers

    What primarily facilitates the mobilization of lipid from adipose tissue into the bloodstream?

    <p>Free fatty acids bound to serum albumin</p> Signup and view all the answers

    Which group of lipoproteins contains the highest percentage of protein?

    <p>High-Density Lipoproteins (HDL)</p> Signup and view all the answers

    What role does the amphipathic nature of phospholipids play in lipoproteins?

    <p>It enables lipoproteins to interact with both lipids and water.</p> Signup and view all the answers

    What metabolic imbalance is often seen in individuals with diabetes mellitus regarding lipid mobilization?

    <p>Excessive mobilization of free fatty acids</p> Signup and view all the answers

    How are lipids made water-miscible to facilitate their transport in blood plasma?

    <p>By associating nonpolar lipids with proteins and phospholipids</p> Signup and view all the answers

    In which cellular component is the main lipid component of lipoproteins primarily synthesized?

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

    What is one of the physiological roles of brown adipose tissue in the body?

    <p>Generating body heat through non-shivering thermogenesis</p> Signup and view all the answers

    What is the effect of the lipid-to-protein ratio on the function of lipoproteins?

    <p>A higher ratio decreases the lipoprotein's density, affecting transport efficiency.</p> Signup and view all the answers

    Which lipoprotein is derived from the intestinal absorption of triacylglycerol and other lipids?

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

    Which characteristic of amphipathic phospholipids is essential for the formation of lipoprotein structures?

    <p>Dual affinity for lipid and aqueous environments</p> Signup and view all the answers

    What condition can result from excessive mobilization of free fatty acids and underutilization of chylomicrons?

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

    What abnormalities can arise from defects in lipoprotein metabolism?

    <p>Hypercholesterolemia and premature atherosclerosis</p> Signup and view all the answers

    Which lipoprotein type is largely responsible for transporting lipids from the liver to peripheral tissues?

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

    What is the consequence of excessive caloric intake during the anabolic phase in omnivores?

    <p>Overproduction of VLDL leading to hypertriglyceridemia</p> Signup and view all the answers

    Which type of lipoprotein is primarily involved in the transport of cholesterol and phospholipids?

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

    What lipid class constitutes the largest fraction of plasma lipids?

    <p>Cholesteryl esters</p> Signup and view all the answers

    Which lipoprotein is characterized by a predominance of triacylglycerols?

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

    What is the primary structural component of the nonpolar core of lipoproteins?

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

    In which lipoprotein category does HDL fall based on its electrophoretic properties?

    <p>α lipoprotein</p> Signup and view all the answers

    Which lipid class has the smallest percentage in plasma lipids?

    <p>Free fatty acids (FFAs)</p> Signup and view all the answers

    What role do high-density lipoproteins (HDL) primarily play in lipid metabolism?

    <p>Involved in reverse cholesterol transport</p> Signup and view all the answers

    Which lipid class is primarily responsible for the export of triacylglycerol from the liver?

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

    Which of the following statements is true regarding the lipid composition of lipoproteins?

    <p>HDL contains a significant amount of phospholipids.</p> Signup and view all the answers

    In the context of plasma lipids, which percentage is associated with triacylglycerols?

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

    Match the following lipoproteins with their primary function:

    <p>Chylomicrons = Transport dietary triacylglycerol to the liver VLDL = Carry lipids from the liver to peripheral tissues LDL = Deliver cholesterol to extrahepatic tissues HDL = Facilitate reverse cholesterol transport to the liver</p> Signup and view all the answers

    Match the lipoprotein class with its primary lipid type:

    <p>Chylomicrons = Triacylglycerol VLDL = Triacylglycerol LDL = Cholesterol HDL = Phospholipids</p> Signup and view all the answers

    Match the following lipoprotein types with their corresponding source:

    <p>Chylomicrons = Intestinal cells VLDL = Liver cells IDL = Metabolized VLDL HDL = Synthesized in liver and intestine</p> Signup and view all the answers

    Match the following apolipoproteins with their associated lipoprotein:

    <p>ApoB100 = Low-density lipoprotein (LDL) ApoE = Chylomicron remnants ApoC-II = Chylomicrons and VLDL ApoA-I = High-density lipoprotein (HDL)</p> Signup and view all the answers

    Match the lipoprotein with its role in atherosclerosis:

    <p>LDL = Promotes atherosclerosis HDL = Retards atherosclerosis Chylomicrons = Not significantly involved VLDL = Can contribute to atherosclerosis</p> Signup and view all the answers

    Match the following lipoproteins with their primary source:

    <p>Chylomicrons = Derived from intestinal absorption of lipids VLDL = Derived from the liver LDL = Derived from metabolism of VLDL HDL = Synthesized by the liver and intestines</p> Signup and view all the answers

    Match the following conditions with their associated lipoprotein metabolism issues:

    <p>Hypertriacylglycerolemia = Excessive mobilization of FFAs due to insulin deficiency Hypercholesterolemia = Inherited defects in lipoprotein metabolism Atherosclerosis = Associated with high levels of LDL Fatty liver disease = Related to excessive intake of FFAs</p> Signup and view all the answers

    Match the following functions with their corresponding lipoproteins:

    <p>Chylomicrons = Transport dietary lipids VLDL = Transport lipids from the liver LDL = Transport cholesterol to tissues HDL = Enhance cholesterol excretion from tissues</p> Signup and view all the answers

    Match the following types of adipose tissue with their functions:

    <p>White adipose tissue = Energy storage Brown adipose tissue = Generation of body heat Subcutaneous fat = Insulation Visceral fat = Protection of internal organs</p> Signup and view all the answers

    Match the following processes with their descriptions:

    <p>Lipid mobilization = Release of fatty acids from adipose tissue Lipoprotein transport = Transport of lipids in blood plasma Insulin deficiency = Leads to excessive lipolysis Caloric balance = Cycle of energy intake and storage</p> Signup and view all the answers

    Study Notes

    Lipid Transport & Storage

    • Lipids, insoluble in water, are transported in blood as lipoproteins, combining nonpolar lipids (triacylglycerol, cholesteryl esters) with amphipathic lipids (phospholipids, cholesterol) and proteins.
    • Four major lipoprotein classes exist: chylomicrons, VLDL, LDL, and HDL.
    • Chylomicrons carry dietary triacylglycerol to the liver, while VLDL carries it from the liver to extrahepatic tissues.

    Lipoprotein Structure

    • Lipoproteins have a nonpolar core (triacylglycerols, cholesteryl esters) surrounded by a single layer of amphipathic lipids (phospholipids, cholesterol).
    • Apolipoproteins (apoproteins) are proteins forming the lipoprotein's protein component, and contribute significantly to lipoprotein structure and function. Apo B-100 and apo E are examples.

    Lipoprotein Metabolism

    • Chylomicrons are metabolized by lipoprotein lipase to chylomicron remnants, then removed by the liver.
    • VLDL is converted to IDL by lipoprotein lipase, then further metabolized to LDL. LDL delivers cholesterol to extrahepatic tissues via LDL receptors.
    • HDL synthesizes and transports cholesterol from extrahepatic tissues back to the liver (reverse cholesterol transport) using SR-B1 receptors.
    • The liver plays a crucial role in lipid transport & metabolism.

    Biomedical Importance

    • Lipid transport is essential for bodily functions and storage.
    • Abnormalities of lipoprotein metabolism lead to various hypo- or hyperlipoproteinemias, such as in diabetes mellitus. Fatty liver disease (NAFLD) can result from fat accumulation in the liver.
    • Free fatty acids (FFAs) are rapidly metabolized by tissues, fulfilling energy requirements or esterifying into triacylglycerols.

    Lipids and Lipoproteins

    • Lipids are transported in chylomicrons (from intestines) and VLDL (from liver).
    • Lipoprotein lipase hydrolyzes triacylglycerol in chylomicrons and VLDL, releasing fatty acids for uptake into tissues.
    • Chylomicron remnants and VLDL remnants (IDL) are cleared by the liver.
    • LDL carries cholesterol to tissues and returns excess to the liver.
    • HDL transports cholesterol from tissues back to liver (Reverse Cholesterol Transport).

    Fatty Liver and Hormones

    • Fatty liver results from excess lipid accumulation in the liver.
    • Increased glucose metabolism reduces FFA output.
    • Insulin inhibits FFA release from adipose tissue; other hormones (epinephrine, glucagon) promote lipolysis.
    • Ethanol consumption can cause fatty liver due to interference with fatty acid oxidation and increased lipogenesis.

    Brown Adipose Tissue

    • Brown adipose tissue (BAT) generates heat.
    • Thermogenin (UCP1) in BAT uncouples ATP synthesis and proton transport, dissipating energy as heat.

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    Test your knowledge on lipid transport and storage, focusing on the structure and function of lipoproteins. This quiz covers key concepts such as the different classes of lipoproteins, their metabolism, and the roles of apolipoproteins in lipid transport.

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