Cell Biology: Integral Membrane Proteins
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Questions and Answers

What is the primary function of the red blood cell membrane in microcirculation?

  • To maintain constant shape regardless of external factors
  • To be tough but flexible and show deformability (correct)
  • To prevent all types of cellular interactions with plasma
  • To store extra nutrients for the cell
  • What characteristic is enabled by the protein cytoskeleton interacting with the membrane lipid bilayer?

  • Deformability of the red blood cell membrane (correct)
  • Permeability to large molecules
  • Energy storage
  • Rigidity of the red blood cell membrane
  • Which of the following is NOT a main function of the red blood cell membrane?

  • Maintain characteristic shape
  • Store genetic information (correct)
  • Regulate intracellular cation concentrations
  • Separate cell contents from plasma
  • What is the shape of erythrocytes?

    <p>Bi-concave disc</p> Signup and view all the answers

    Which lipid is NOT part of the 60% phospholipid composition of the red cell membrane?

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

    Which integral protein facilitates anion transport across the red cell membrane?

    <p>Band 3</p> Signup and view all the answers

    Which component of the red cell membrane is characterized by polar head groups attached to non-polar fatty tails?

    <p>Lipid Bilayer</p> Signup and view all the answers

    What percentage of the red cell membrane's chemical structure is composed of carbohydrates?

    <p>7%</p> Signup and view all the answers

    Where do red blood cells develop?

    <p>Bone marrow</p> Signup and view all the answers

    What is the average lifespan of a red blood cell in the blood circulation?

    <p>120 days</p> Signup and view all the answers

    Which protein facilitates glucose diffusion across the cell membrane?

    <p>GLUT-1</p> Signup and view all the answers

    What results from the phosphorylation of the Na+/K+ ATPase pump?

    <p>3 Na+ are transported out of the cell</p> Signup and view all the answers

    Which disorder is characterized by the absence of Rh polypeptides and RhAG in the membrane?

    <p>Rh Null Syndrome</p> Signup and view all the answers

    What is the main function of ankyrin in the cytoskeleton?

    <p>Anchors spectrin molecules to the lipid bilayer</p> Signup and view all the answers

    What subunit binding pattern is associated with spectrin?

    <p>Anti-parallel arrangement</p> Signup and view all the answers

    What happens to glucose after it binds to GLUT-1 on the outside of the cell?

    <p>It causes a conformational change in GLUT-1 and is translocated inside the cell</p> Signup and view all the answers

    Which protein directly binds to glycophorin A and C?

    <p>Band 4.1</p> Signup and view all the answers

    Which primary membrane disorder results in the presence of a large proportion of oval or elliptical cells?

    <p>Hereditary Elliptocytosis</p> Signup and view all the answers

    What results from the dephosphorylation of the Na+/K+ ATPase pump?

    <p>2 K+ are transported into the cell</p> Signup and view all the answers

    Which of the following proteins is not part of the cytoskeleton's peripheral proteins?

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

    Study Notes

    Integral Proteins

    • Glycophorin A: a sialoglycoprotein that provides negative charge and acts as a binding site for viruses, bacteria, and parasites
    • Glucose Transport Protein (GLUT 1): facilitates glucose diffusion across the membrane with 12 trans-membrane domains
    • Band 3: facilitates anion transport across the membrane and has binding sites for Hb, ankyrin, Band 4.1, and Band 4.2

    Representation of Membrane Structure

    • Phospholipid Monolayer: a basic phospholipid bilayer that acts as a permeability barrier
    • Spectrin Tetramer: a protein that forms a 2D lattice in the cytoskeleton
    • Ankyrin Complex: a protein that anchors spectrin molecules to the lipid bilayer
    • 4.1-R Complex: a protein that binds to spectrin close to the actin binding site

    Pump

    • Na+/K+ ATPase: an enzyme composed of 3 protein subunits that catalyzes the conversion of ATP to ADP to release energy
    • Function of Na+/K+ ATPase: transports 3 Na+ molecules out of the cell and 2 K+ molecules into the cell, maintaining ion balance

    Mechanism of Na+/K+ ATPase

    • Phosphorylation: transports 3 Na+ molecules out of the cell
    • Dephosphorylation: transports 2 K+ molecules into the cell

    Primary Membrane Disorders

    • Hereditary Spherocytosis: an autosomal inherited disorder that affects spectrin, causing spherocytosis and hemolytic anemia
    • Hereditary Elliptocytosis: a disorder that causes elliptical red blood cells due to defective spectrin, Band 4.1, or Band 3
    • Rh Null Syndrome: a disorder that causes the absence of Rh polypeptides and RhAG in the membrane, leading to stomatocytosis and spherocytosis

    Red Cell Membrane

    • Functions: separates cell contents from plasma, maintains shape, regulates intracellular cation concentrations, and is a site for membrane surface receptors
    • Composition: 44% lipid, 49% protein, and 7% carbohydrate
    • Glycocalyx: an outer carbohydrate "coat" made up of extracellular proteins and glycosylated proteins and lipids from the lipid bilayer

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    Description

    Learn about integral membrane proteins, specifically glycophorin A and glucose transport protein (GLUT 1), and how they facilitate glucose diffusion in cells.

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