L1 Synthesis of membrane lipids and sphingolipidoses
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Questions and Answers

What is the primary consequence of sphingomyelinase enzyme deficiency?

  • Accumulation of sphingomyelin in the reticuloendothelial system (correct)
  • Accumulation of sphingomyelin only in the central nervous system
  • Accumulation of sphingomyelin in the liver only
  • Accumulation of sphingomyelin in muscle tissues

    • Which of the following pairs a disease with its associated enzyme deficiency correctly?

  • Hurler syndrome - iduronate transferase deficiency
  • Krabbe disease - α-glucosidase deficiency
  • Pompe disease - glucosyltransferase deficiency
  • Fabry disease - α-galactosidase deficiency (correct)

    • Which symptom is most commonly associated with Hurler syndrome?

  • Cloudy cornea and skeletal deformities (correct)
  • Skin eruptions such as angiokeratomas
  • Psychomotor delays and irritability
  • Enlarged liver without joint stiffness

    • What is the main difference in inheritance patterns between Hunter syndrome and Hurler syndrome?

    <p>Hunter syndrome is X-linked recessive and Hurler syndrome is autosomal recessive</p> Signup and view all the answers

    Which of the following diseases results from a deficiency of the arylsulfatase A enzyme?

    <p>Metachromatic leukodystrophy</p> Signup and view all the answers

    What is a common symptom of Krabbe disease?

    <p>Motor developmental delays and hypotonia</p> Signup and view all the answers

    What is the main structural component of cell membranes according to lipid classification?

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

    Which of the following statements about sphingolipid synthesis is true?

    <p>It is connected to both ceramide synthesis and lysosomal storage diseases.</p> Signup and view all the answers

    Which cell type has a high capacity for phospholipid synthesis specifically for surfactant production?

    <p>Type II cells of the lung</p> Signup and view all the answers

    What is the role of liver in phospholipid synthesis?

    <p>It generates phospholipids for bile secretion and plasma lipoproteins.</p> Signup and view all the answers

    What characterizes the polar head group of glycerophospholipids?

    <p>It contains a phosphate and can be various different molecules.</p> Signup and view all the answers

    Which of the following best describes the initiation of glycerophospholipid synthesis?

    <p>Begins with phosphatidic acid from glycerol-3-phosphate.</p> Signup and view all the answers

    What is the clinical significance of surfactant in the lungs?

    <p>It prevents alveolar collapse by reducing surface tension.</p> Signup and view all the answers

    In which cellular organelle does phospholipid synthesis primarily occur?

    <p>Cytosolic face of ER and Golgi</p> Signup and view all the answers

    Which of the following diseases is commonly associated with sphingolipid synthesis or breakdown?

    <p>Lysosomal storage diseases</p> Signup and view all the answers

    What is the primary role of lung surfactant in relation to alveoli?

    <p>It prevents alveoli from collapsing during expiration.</p> Signup and view all the answers

    What condition is commonly associated with a deficiency of surfactant in premature infants?

    <p>Neonatal respiratory distress syndrome</p> Signup and view all the answers

    What is the underlying enzyme deficiency in Gaucher disease?

    <p>β-glucocerebrosidase</p> Signup and view all the answers

    Which disease is characterized by cherry-red spots in the eyes and developmental delay?

    <p>Tay-Sachs disease</p> Signup and view all the answers

    Which phospholipid is identified as a major component of surfactant?

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

    Which cell type is responsible for myelination in the central nervous system?

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

    What is the main cause of easy bruising in Gaucher disease?

    <p>Low blood platelet count</p> Signup and view all the answers

    What happens to nerve conduction when there is demyelination of axons?

    <p>It is interfered, leading to sensory loss and weakness.</p> Signup and view all the answers

    In which condition is the enzyme hexosaminidase A deficient?

    <p>Tay-Sachs disease</p> Signup and view all the answers

    Which of the following symptoms is NOT commonly associated with Niemann-Pick disease?

    <p>Muscle atrophy</p> Signup and view all the answers

    Which fatty acid is commonly cleaved off by PLA2 during lipid degradation?

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

    What is the role of the blood-brain barrier regarding fatty acids?

    <p>It restricts the entry of non-essential fatty acids.</p> Signup and view all the answers

    Which of the following diseases commonly affects individuals of Ashkenazi Jewish descent?

    <p>Tay-Sachs disease</p> Signup and view all the answers

    A 6-month-old girl with failure to thrive and hepatosplenomegaly may likely have which condition?

    <p>Niemann-Pick disease</p> Signup and view all the answers

    What is the daily lipid synthesis requirement for oligodendrocytes to maintain myelin structure?

    <p>4X its own weight</p> Signup and view all the answers

    Which enzyme deficiency is responsible for fatty acyl carnitine accumulation in MCAD deficiency?

    <p>Acyl-CoA dehydrogenase</p> Signup and view all the answers

    What contributes to the tight packing of myelin in the peripheral nervous system?

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

    What metabolic substance accumulates due to a deficiency in β-glucocerebrosidase?

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

    What is the effect of phospholipase A1 on glycerophospholipids?

    <p>It removes the fatty acid group on C1.</p> Signup and view all the answers

    Which of the following diseases would be associated with an enzyme that hydrolyzes ganglioside GM2?

    <p>Tay-Sachs disease</p> Signup and view all the answers

    What are the second messengers produced when PLC cleaves Phosphatidylinositol 4,5-bisphosphate (PIP2)?

    <p>Diacylglycerol and inositol triphosphate</p> Signup and view all the answers

    Which molecule is the central molecule on which sphingolipids are based?

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

    What type of lipids are formed when ceramide reacts with UDP-sugars?

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

    Which of the following is NOT related to the clinical importance of sphingolipids?

    <p>Sphingomyelin as a precursor of ceramide</p> Signup and view all the answers

    What occurs when cholera toxin's A subunit is endocytosed into the cytoplasm?

    <p>It ADP-ribosylates the Gα subunit, making it constitutively active.</p> Signup and view all the answers

    What is the result of increased intracellular cAMP concentrations due to cholera toxin activity?

    <p>Increased secretion of electrolytes into the lumen</p> Signup and view all the answers

    What type of diseases are associated with deficiencies in lysosomal enzymes that degrade sphingolipids?

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

    What is the fate of GM1 gangliosides in relation to cholera toxin?

    <p>They enhance the binding of cholera toxin to intestinal cells.</p> Signup and view all the answers

    What is a structural consequence of serine condensing with palmitoyl CoA during sphingolipid synthesis?

    <p>Formation of sphingosine</p> Signup and view all the answers

    What is likely the condition of a patient with a history of progressive hepatosplenomegaly and characteristic cells upon bone marrow biopsy?

    <p>Accumulation of glycosphingolipids</p> Signup and view all the answers

    Which of the following characteristics is associated with Niemann-Pick Type C disease?

    <p>Impairs lipid transport</p> Signup and view all the answers

    What condition results from a deficiency of the lysosomal enzyme α-galactosidase?

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

    Which of the following is a common clinical manifestation of Metachromatic leukodystrophy?

    <p>Memory loss and gait disturbances</p> Signup and view all the answers

    Hurler syndrome is primarily associated with which of the following symptoms?

    <p>Spinal deformities and stiff joints</p> Signup and view all the answers

    What is a key feature of I-cell disease related to its enzyme deficiency?

    <p>Deficiency of UDP-N-acetylglucosamine-1-phosphate transferase</p> Signup and view all the answers

    Which of the following correctly describes the inheritance pattern of Hunter syndrome?

    <p>X-linked recessive</p> Signup and view all the answers

    Which class of membrane lipids is characterized by having a glycerol backbone, two fatty acid tails, and a phosphate group?

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

    What is the initial molecule formed during the synthesis of glycerophospholipids?

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

    Which cell type is primarily responsible for the synthesis of surfactant phospholipids in the lungs?

    <p>Type II alveolar cells</p> Signup and view all the answers

    What is the major metabolic site for the synthesis of phospholipids utilized for bile secretion?

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

    Which polar head groups can be found in glycerophospholipids?

    <p>Choline and inositol</p> Signup and view all the answers

    What is the primary function of lung surfactant in relation to alveoli?

    <p>Prevent alveolar collapse</p> Signup and view all the answers

    Which of the following processes is characterized by the degradation of glycerophospholipids?

    <p>Phospholipase activity</p> Signup and view all the answers

    Which lipid acts as the central molecule in the synthesis of sphingolipids?

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

    What is a common result of dysfunction in sphingolipid synthesis or breakdown?

    <p>Lysosomal storage diseases</p> Signup and view all the answers

    Which of the following best describes an enzyme deficiency leading to the accumulation of glucocerebroside?

    <p>Deficiency of glucocerebrosidase</p> Signup and view all the answers

    What is a distinguishing symptom associated with Tay-Sachs disease?

    <p>Cherry-red spots in the eye</p> Signup and view all the answers

    What clinical presentation is most consistent with Niemann-Pick disease?

    <p>Hepatosplenomegaly with normal motor development</p> Signup and view all the answers

    What enzyme deficiency is primarily responsible for the symptoms seen in Gaucher disease?

    <p>β-glucocerebrosidase</p> Signup and view all the answers

    Which syndrome is associated with a deficiency of iduronate sulfatase?

    <p>Hunter syndrome</p> Signup and view all the answers

    What biochemical compound primarily accumulates in Tay-Sachs disease due to hexosaminidase A deficiency?

    <p>GM2 gangliosides</p> Signup and view all the answers

    In which condition is the enzyme sphingomyelin phosphodiesterase 1 deficient?

    <p>Niemann-Pick disease</p> Signup and view all the answers

    What symptom is typically NOT associated with Gaucher disease?

    <p>Cherry-red spots in the eye</p> Signup and view all the answers

    Which of these conditions exhibits symptoms common in Ashkenazi Jews?

    <p>Tay-Sachs disease</p> Signup and view all the answers

    What clinical finding is most likely in a 6-month-old baby with developmental delays due to enzyme deficiency?

    <p>Difficulty lifting head</p> Signup and view all the answers

    What is the main role of lung surfactant in the respiratory system?

    <p>To facilitate the opening of alveoli during inspiration</p> Signup and view all the answers

    Which condition is primarily caused by a deficiency in lung surfactant?

    <p>Neonatal respiratory distress syndrome</p> Signup and view all the answers

    What specific cell type is crucial for synthesizing surfactant in the lungs?

    <p>Type II epithelial cells</p> Signup and view all the answers

    Which factor contributes to the tight packing of myelin in the peripheral nervous system?

    <p>Role of Schwann cells in myelination</p> Signup and view all the answers

    Which lipids play a major role in myelin formation within the central nervous system?

    <p>Very long chain fatty acids</p> Signup and view all the answers

    What characterizes the response of phospholipase A2 during lipid degradation?

    <p>It often releases arachidonic acid from phospholipids</p> Signup and view all the answers

    The degradation of which specific lipids leads to the development of multiple sclerosis?

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

    What is the synthesis requirement of oligodendrocytes to maintain myelin structure?

    <p>4X their own weight in lipids per day</p> Signup and view all the answers

    What role does the blood-brain barrier play concerning fatty acids?

    <p>It prevents the entry of non-essential fatty acids</p> Signup and view all the answers

    Which symptom is associated with demyelination caused by multiple sclerosis?

    <p>Sensory loss</p> Signup and view all the answers

    What are the second messengers produced by the cleavage of Phosphatidylinositol 4,5-bisphosphate (PIP2) via PLC?

    <p>Diacylglycerol (DAG) and inositol triphosphate (IP3)</p> Signup and view all the answers

    Which of the following best describes the synthesis of sphingomyelin?

    <p>Synthesized from ceramide and phosphatidylcholine</p> Signup and view all the answers

    What type of molecules result from the reaction of ceramide with UDP-sugars?

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

    Which clinical condition is associated with deficiencies of lysosomal enzymes that degrade sphingolipids?

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

    What is a significant role of glycolipids found at the outer leaflet of the plasma membrane?

    <p>Cell adhesion and cell-cell interactions</p> Signup and view all the answers

    What results from increased intracellular cAMP concentrations due to cholera toxin activity?

    <p>Activation of CFTR leading to sodium and water retention</p> Signup and view all the answers

    What is the abnormally accumulated material in cells of a patient with progressive hepatosplenomegaly and characteristic symptoms?

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

    What type of gangliosides serves as receptors for bacterial toxins such as cholera toxin?

    <p>GM1 gangliosides</p> Signup and view all the answers

    Which fatty acid is involved in the condensation steps to form ceramide?

    <p>Palmitoyl CoA</p> Signup and view all the answers

    What reaction occurs to sphingolipids at the outer membrane and influences cell interactions?

    <p>Modification to form higher order sphingolipids</p> Signup and view all the answers

    Study Notes

    Synthesis of Membrane Lipids

    • Sphingolipidoses are diseases related to the synthesis and breakdown of sphingolipids.
    • Pages 699-706 and 1037-1041 of Marks' Basic Medical Biochemistry, 6th Ed. detail these processes.
    • Biochemistry, Cell and Molecular Biology, and Genetics, Part VI, Chapter 41 (pages 348-354) also cover this topic.
    • Sphingolipids are crucial components of cell membranes and play roles in cell-cell interactions and as antigenic determinants.

    Learning Objectives

    • Understanding the major membrane lipids and their cellular functions is essential.
    • Glycerophospholipid synthesis, along with the importance of surfactant, is a crucial component.
    • Glycerophospholipid degradation and relevant enzymes need to be understood.
    • Sphingolipid and ceramide synthesis should be outlined.
    • Recognizing and distinguishing lysosomal storage diseases (sphingolipidoses) is paramount.
    • The clinical significance of sphingolipids in various diseases, including sphingolipidoses, needs attention

    Glycerolipids and Sphingolipids

    • Glycerolipids include triacylglycerols, stored in adipose tissue and blood lipoproteins.
    • Glycerophospholipids (phospholipids) are major components of cell membranes, including phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol bisphosphate (PIP2), phosphatidylglycerol, and cardiolipin.
    • Sphingolipids include sphingophospholipids (such as sphingomyelin) and glycolipids (such as cerebrosides, sulfatiides, globosides, and gangliosides).
    • The structure of each lipid is described, highlighting the polar head group and nonpolar tails.
    • Specific examples of sphingolipids and structures involved in synthesis and degradation are provided.

    Glycerophospholipids

    • Glycerophospholipids are abundant in cell membranes and are the main structural components and are associated with a variety of proteins.
    • The structure consists of two fatty acid tails attached to a glycerol backbone, plus a phosphate group and a highly polar head group.
    • The hydrophobic fatty acid tails face inward, while the hydrophilic head groups face outward. This orientation allows interaction with water in the cell.

    Synthesis of Glycerophospholipids

    • Initial synthesis steps mimic those of triacylglycerol synthesis.
    • Glycerol-3-phosphate reacts with two fatty acyl-CoA molecules to form phosphatidic acid.
    • Subsequent reactions convert phosphatidic acid into specific glycerophospholipids.

    Synthesis of Glycerophospholipids (continued)

    • Cells, excluding mature red blood cells, synthesize phospholipids.
    • Synthesis occurs primarily on the cytosolic surface of the ER and Golgi complex.
    • The liver is a major site for phospholipid synthesis.
    • Phospholipids are essential for bile production, and for coating lipoproteins.
    • Type II lung cells specialize in surfactant production.

    Lung Surfactant

    • Comprised of predominantly phospholipids, surfactant prevents alveolar collapse.
    • Surfactant reduces surface tension in the alveoli, facilitating lung inflation.
    • Dipalmitoylphosphatidylcholine is the major phospholipid component of lung surfactant.

    Lack of Surfactant

    • Lack of surfactant in premature infants can lead to neonatal respiratory distress syndrome (RDS).
    • Immature lungs may not produce sufficient surfactant, leading to difficulties in breathing.

    Membrane Lipids in the Brain and Peripheral Nervous System

    • Blood-brain barrier restricts non-essential fatty acid entry; essential fatty acids are absorbed.
    • Virtually all nerve system lipids are manufactured within the central nervous system (CNS), including cholesterol, fatty acids, sphingolipids, and phospholipids.
    • The very long-chain fatty acids produced within the brain are major components of myelin.
    • Myelin consists of multiple layers of tightly packed lipids, ensuring fast nerve impulse transmission.
    • Myelin formation and maintenance are specifically described.

    Loss of Phospholipids and Sphingolipids

    • Loss of phospholipids and sphingolipids in the brain and spinal cord is associated with multiple sclerosis.
    • Demyelination affects nerve conduction and can cause a range of neurological problems, including sensory loss, weakness, muscle cramps, autonomic dysfunctions (bladder, bowel, sexual), and cognitive decline.

    Degradation of Glycerophospholipids

    • Phospholipases are enzymes responsible for breaking down glycerophospholipids into smaller components.
    • PLA1 removes a fatty acid at C1 position.
    • PLA2 removes a fatty acid at C2 position, crucial for the production of eicosanoids.
    • PLC hydrolyzes phosphatidylinositol phosphate.
    • Many reactions involving these enzymes take place in membranes or lysosomes.
    • Specific examples of phospholipases are provided (PLA1, PLA2, PLC).

    Sphingolipids

    • Sphingolipids are based on ceramide.
    • Ceramide is constructed from sphingosine and a fatty acid.
    • Sphingomyelin is formed by the reaction of ceramide with phosphocholine.
    • Cerebrosides are synthesized from ceramide and a sugar (e.g., glucose or galactose).
    • Additional sugars lead to globosides and gangliosides.
    • The metabolic pathway and reaction pathways associated with sphingolipids synthesis are outlined and described.

    Clinical Importance of Sphingolipids

    • Glycolipids function in cell-cell interactions.
    • Some glycolipids act as antigens (e.g., ABO groups).
    • Certain gangliosides are bacterial toxin receptors (e.g., cholera toxin).
    • Sphingolipids are degraded within the lysosomes.
    • Sphingolipidoses are lysosomal storage diseases caused by enzyme deficiencies that affect sphingolipid breakdown.
    • Specific examples of sphingolipidoses (Niemann-Pick, Fabry, Krabbe, Gaucher, Tay-Sachs, and Metachromatic leukodystrophy) their associated enzyme deficiencies, accumulated products, and clinical consequences.

    GM1 Gangliosides

    • GM1 gangliosides are the binding sites for cholera toxin and certain E. coli toxins.
    • The toxin A subunit enters cells, affecting cellular pathways and causing fluid loss.

    Sphingolipidoses (continued)

    • Each sphingolipidosis is associated with the deficiency of a specific enzyme involved in sphingolipid degradation.
    • Defective enzymes lead to accumulation of specific sphingolipid metabolites.
    • These metabolites cluster in lysosomes , tissues, especially the brain, and trigger a variety of symptoms and clinical manifestations.
    • The clinical manifestation and consequences of the different sphingolipidoses are further described.

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    Description

    This quiz covers the synthesis and degradation of membrane lipids, focusing on glycerophospholipids and sphingolipids. It outlines the cellular functions of major lipids and discusses lysosomal storage diseases such as sphingolipidoses. Reference pages from Marks' Basic Medical Biochemistry and designated chapters in Cell and Molecular Biology provide essential insights.

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