Biochemistry of Lipids and Lipoproteins
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Questions and Answers

What is one of the key functions of phospholipids?

  • Hormone production
  • Energy storage
  • Structural component of membranes (correct)
  • Muscle contraction

    • Cholesterol is unimportant for the body and has no functions.

    False

    What are lipoproteins primarily involved in?

    Lipid transport in the body.

    Cephalins are comprised of phosphatidyl __________ and phosphatidyl ethanolamine.

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

    Match the following types of lipoproteins with their primary functions:

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

    What can a defect in lipoprotein function lead to?

    <p>Fatty liver</p> Signup and view all the answers

    Antibodies against acidic phospholipids can cause recurrent thrombosis.

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

    Name a special function of dipalmitoyl phosphatidylcholine.

    <p>It acts as a lung surfactant.</p> Signup and view all the answers

    What is the primary component of the steroid nucleus?

    <p>Four rings of carbons</p> Signup and view all the answers

    Cholesterol is the major steroid found in plant tissues.

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

    What are chylomicrons primarily responsible for transporting?

    <p>Dietary triacylglycerols and cholesterol</p> Signup and view all the answers

    The major carriers of endogenous triacylglycerols are _____ lipoproteins.

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

    Match the lipoproteins with their primary function:

    <p>Chylomicrons = Transport dietary lipids VLDL = Transport endogenous triacylglycerols LDL = Transport cholesterol to tissues HDL = Reverse cholesterol transport</p> Signup and view all the answers

    Which component is NOT part of a lipoprotein structure?

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

    Cholesterol can exist in both free form and ester form in the blood.

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

    What is the predominant lipid in nascent chylomicrons?

    <p>Dietary triacylglycerol</p> Signup and view all the answers

    What is the primary function of HDL in the body?

    <p>Transporting cholesterol from tissues to the liver</p> Signup and view all the answers

    Higher levels of HDL in serum are related to an increased risk of myocardial infarction.

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

    What are coated pits?

    <p>Regions in the cell membrane specialized for endocytosis.</p> Signup and view all the answers

    The __________ is the sum of all biochemical reactions occurring in a cell.

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

    Match the metabolic process with its definition:

    <p>Catabolic = Break down complex molecules into simpler ones Anabolic = Combine small molecules to form complex molecules Amphibolic = Processes that can be both anabolic and catabolic</p> Signup and view all the answers

    What type of metabolic pathway primarily involves ATP production?

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

    The main transport form of HDL particles contains significant amounts of cholesterol.

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

    What is the importance of metabolic integration?

    <p>It allows various metabolic pathways to work together efficiently and respond to the needs of the cell.</p> Signup and view all the answers

    Which statement accurately describes the nature of anabolic pathways?

    <p>They convert simple molecules into complex ones.</p> Signup and view all the answers

    Catabolic pathways primarily involve reductions.

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

    What is an example of a metabolic pathway that has both anabolic and catabolic functions?

    <p>TCA cycle</p> Signup and view all the answers

    Anabolic pathways generally require _______ as an electron donor.

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

    Match the regulatory mechanisms to their descriptions:

    <p>Allosteric regulation = Regulation through feedback inhibition or activation Covalent modification = Change in enzyme activity via phosphorylation or dephosphorylation Gene induction = Increase in enzyme synthesis Gene repression = Decrease in enzyme synthesis</p> Signup and view all the answers

    Which of the following is a factor that regulates metabolic pathways?

    <p>Enzyme quantity</p> Signup and view all the answers

    The TCA cycle predominantly occurs in the cytosol.

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

    What hormonal control influences enzyme phosphorylation during fasting?

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

    What is the first step in the process of signal transduction?

    <p>Recognition of signal by specific receptors</p> Signup and view all the answers

    CAMP is considered a second messenger in the signaling pathway by glucagon.

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

    Name the enzyme that converts ATP into cAMP.

    <p>adenylyl cyclase</p> Signup and view all the answers

    The activation of protein kinase A is dependent on _____ formed from cAMP.

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

    Match the following components of the glucagon signaling pathway:

    <p>Glucagon = Stimulus for signaling Glycogen Synthase = Inactive form Glycogen Phosphorylase = Active form Phosphodiesterase = Degrades cAMP</p> Signup and view all the answers

    What is the result of glucagon's effect on glycogen synthase?

    <p>Inhibition of glycogenesis</p> Signup and view all the answers

    The termination of the glucagon signal involves the activation of G-protein.

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

    What happens to blood glucose levels as a result of glucagon signaling?

    <p>Increase in blood glucose levels</p> Signup and view all the answers

    Which component of the cell membrane is responsible for modulating membrane fluidity?

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

    Integral proteins can be easily removed from the membrane without disrupting its structure.

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

    What are the major classes of membrane lipids?

    <p>Phospholipids, Glycolipids, Cholesterol</p> Signup and view all the answers

    The lipid component called __________ is found in brain and nerve cell membranes.

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

    Match each type of protein with its description:

    <p>Peripheral proteins = Can be removed without disrupting the membrane Integral proteins = Amphipathic and deeply embedded in the bilayer Glycoproteins = Proteins covalently linked to carbohydrates Glycolipids = Lipids with carbohydrate chains attached</p> Signup and view all the answers

    What is the primary role of carbohydrates in the cell membrane?

    <p>Inhibit random cell proliferation</p> Signup and view all the answers

    Phospholipids have hydrophobic tails and hydrophilic heads.

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

    Name one type of glycolipid mentioned in the lecture.

    <p>Glycolipids can include many varieties, but examples include cerebrosides and gangliosides.</p> Signup and view all the answers

    Study Notes

    Course Information

    • Course Name: BMS 131
    • Lecture Number: 10
    • Course Title: Lipid Chemistry 2
    • Instructor: Dr Wael Elayat
    • University: GALALA UNIVERSITY
    • Program: Medicine and Surgery Program
    • Year: Fall 2024

    Intended Learning Outcomes (ILOs)

    • Students will identify the significance of phospholipids.
    • Students will define cholesterol and its importance.
    • Students will define lipoproteins.
    • Students will list different types of lipoproteins and their functions.
    • Students will explain the relationship between different types of lipoproteins and atherosclerosis.

    Functions of Phospholipids

    • Structural component of membranes
    • Aid in lipoprotein structure, facilitating lipid transport from the liver to the body; defects can lead to fatty liver.
    • Solubilize cholesterol in bile; defects can lead to cholesterol stones.
    • Special functions
      • DiPalmitoyl Phosphatidylcholine (DPPC): Lung surfactant
      • Cephalins: mixture of phosphatidyl serine and phosphatidyl ethanolamine, found in liver and brain, vital in blood clotting and clot lysis. Defects in these systems can cause recurrent thrombosis and recurrent fetal loss (antiphospholipid syndrome).

    Special Function of Phospholipids

    • DiPalmitoyl Phosphatidylcholine (DPPC) is a key component of lung surfactant.
    • Dipalmityl lecithin is important lung surfactant.
    • Cephalins are important in blood coagulation.

    Derived Lipids

    • Produced by the hydrolysis of simple or conjugated lipids, or associated with lipids by nature.
    • Examples:
      • Alcohols
      • Fatty acids
      • Steroids
      • Glycerol (in triacylglycerol – TAG)
      • Phosphoglycerides
      • Vitamin A and D

    Steroids

    • Compounds with a steroid nucleus
    • Steroid nucleus is composed of 4 rings (A, B, C, D) and 19 carbons.

    Cholesterol

    • Major steroid in animal tissue
    • Biological importance through its role in bile acids, vitamin D, and steroid hormones.

    Cholesterol-Biological Important Components

    • Cholesterol is a key precursor for bile acids.
    • Cholesterol is crucial for vitamin D synthesis.
    • Cholesterol is a fundamental component in the production of steroid hormones.

    i-Cholesterol Structure

    • A steroid nucleus with an 8-carbon side chain at C-17.
    • A double bond between C5 and C6.
    • A hydroxyl group (OH) at C3.
    • Amphipathic (having both hydrophilic and hydrophobic properties)

    Cholesterol Ester

    • Formed by esterifying cholesterol with unsaturated fatty acids.
    • Storage form of cholesterol within cells.
    • Blood cholesterol is present as either free cholesterol or cholesterol ester.

    Lipoproteins

    • Transport structure for insoluble lipids in the bloodstream.
    • Structure: Hydrophobic core of triacylglycerols (TAGs) and cholesterol esters, with a hydrophilic outer layer of phospholipids, free cholesterol, and proteins.

    Classification of Plasma Lipoproteins

    • Four major types: chylomicrons, VLDL, LDL, and HDL, distinguished by size and density, determined via ultracentrifugation and electrophoresis.

    Chylomicrons

    • Assembled in intestinal mucosal cells and secreted into the lymphatic system.
    • Transport dietary triacylglycerols and cholesterol to tissues.
    • The protein component includes apo B48.
    • Important for post-alimentary lipemia.

    VLDL

    • Major carriers of endogenous triacylglycerols,produced by liver cells.

    • Acquire apo C and apo E from circulating HDL.

    • Converted to IDL or VLDL remnant.

    IDL

    • Fate:
      • Converted to LDL.
      • Directly taken up by the liver.

    LDL

    • Formed from VLDL, small particles, rich in cholesterol
    • Transport cholesterol from liver to peripheral tissues.
    • High blood LDL levels are linked to heart disease.

    LDL Receptor

    • Located in coated pits in the cell membrane.
    • Vital for cholesterol uptake.

    HDL

    • Transports cholesterol from peripheral tissues to the liver (reverse cholesterol transport).
    • Inverse relationship between HDL levels and incidence of myocardial infarction.
    • Secreted from the liver as discoidal nascent particles with relatively little cholesterol, phospholipids, and apoproteins (A, C, & E).

    Metabolism

    • Sum of biochemical reactions in cells, tissues, and the entire organism.
    • Composed of interconnected pathways.
    • Different pathways often intersect to form the integrated network in the Metabolic map.

    Metabolic Pathways: Types

    • Catabolic Pathways:
    • Break down complex molecules into smaller ones, releasing energy.
    • Energy-producing (exergonic)
    • Usually oxidative reactions requiring hydrogen carriers (e.g., NAD+, FAD).
    • Convergent process: many different molecules are broken down into a few common end products (e.g., Acetyl CoA).
    • Anabolic pathways
    • Build complex molecules from smaller ones, and requires energy.
    • Energy-consuming (endergonic)
    • Usually reductive reactions using electron donors (e.g., NADPH).
    • Divergent process: Few starting precursors form a wide variety of complex products.
    • Amphibolic pathways:
    • Have dual function (both anabolic and catabolic).
    • TCA (tricarboxylic acid) cycle is most important example.

    Metabolic Pathway Regulation

    • Regulation via:
      • Enzymatic activity: - Alter enzyme quantity (long-term) through gene induction or repression under hormonal control
        - Alter enzyme activity (short-term) through allosteric regulation, covalent modification.
      • Compartmentation: Isolation of different steps in metabolism within different cellular compartments like the cytosol and mitochondrial matrix.
      • Energy state and substrate availability.

    Signal Transduction

    • Process by which extracellular signals converted into intracellular changes
    • Crucial process for communication between cells.
    • Primarily involves receptor activation, second messenger production (e.g., cAMP), and target protein activation.
    • Signals include: hormones, neurotransmitters, growth factors, etc.

    Adenylate Cyclase Signaling by Glucagon

    • Glucagon is the primary signal.
    • Adenylyl Cyclase is the enzyme.
    • cAMP is the second messenger.
    • PKA (protein kinase A) is activated by cAMP.

    Termination of Signal

    • Removal of the signal: Deactivation via various mechanisms, for example,
      • Dephosphorylation of proteins via phosphatases.
      • Degradation of PKA.
      • Conversion of cAMP into AMP
    • Hereditary disorder.
    • Affected chloride channels in the epithelial cells of the GIT and respiratory tracts
    • Result in thick mucus that can obstruct the GIT and respiratory tract, and also increase bacterial infection risk.

    Cell Membrane (Biological)

    • Membranes are essential for cell function, providing borders and gates.
    • Highly selective and semi-permeable.
    • Membranes allow information transfer with receptors and specialized channels. Crucial function in cell communication and transport.

    Cell Membrane Composition

    • Composed of:
      • Lipids
        • Phospholipid bilayer
        • Glycolipid
        • Cholesterol
      • Proteins
        • Peripheral proteins
        • Integral proteins
      • Carbohydrates
        • Oligosaccharides covalently attached to proteins and lipids.

    Chemical Composition of Membrane Lipids

    • Phospholipids: major component; amphipathic molecules with hydrophobic tails and hydrophilic heads. Specialized to form the cell membrane's bilayer. Includes lecithin, cephalins, phosphatidyl inositol, etc.
    • Cholesterol: amphipathic, regulates membrane fluidity.
    • Glycolipids: exterior surface of cell membrane, role in cell proliferation and cell recognition. Types include sphingolipids.

    Membrane Proteins

    • Peripheral: located at surface; easily removed
    • Integral: embedded in the membrane; require detergents or organic solvents for removal

    Membrane Carbohydrates

    • Found externally on the cell membrane (exclusively external)
    • Typically are covalently attached to protein (glycoprotein) or lipid( glycolipids)
    • Play a significant role in cell-cell recognition, communication, proliferation
    • Important in disease states like cancer cell proliferation control as it influences their ability to proliferate.
    • Part of blood type system (ABO)

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    BMS 131 Lecture 10: Lipid Chemistry 2 - Fall 2024 PDF

    Description

    Explore the intricate roles of phospholipids, cholesterol, and lipoproteins in the body. This quiz covers key functions, structural components, and the implications of defects in lipoprotein functions. Test your knowledge on lipid biochemistry and its importance in human physiology.

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