Cell Biology Chapter: Membrane Proteins
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Questions and Answers

Which type of protein extends across the lipid bilayer?

  • Covalently attached proteins
  • Transmembrane proteins (correct)
  • Peripheral proteins
  • Lipid-anchored proteins

    • How are some membrane proteins anchored to the cytosolic half of the lipid bilayer?

  • By an amphipathic α helix (correct)
  • By a single β sheet
  • Through a transmembrane helix
  • Using hydrogen bonds

    • What connects some proteins to either side of the bilayer?

  • Hydrophobic interactions
  • Covalently attached lipid molecules (correct)
  • Hydrogen bonding
  • Electrostatic interactions

    • What type of interactions often attaches proteins to the membrane weakly?

    <p>Noncovalent interactions</p> Signup and view all the answers

    Which type of protein association is characterized by being solely linked through weak interactions?

    <p>Peripheral proteins</p> Signup and view all the answers

    What is the primary function of the plasma membrane?

    <p>To serve as a continuous barrier between cytoplasm and the external environment</p> Signup and view all the answers

    Which of the following structures is involved in the production of ATP?

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

    Internal membranes within a cell are primarily responsible for which of the following?

    <p>Dividing the cell into functional compartments</p> Signup and view all the answers

    What role do enzymes play in the internal membranes?

    <p>They are involved in the cell's metabolism</p> Signup and view all the answers

    Which organelle is responsible for sorting and modifying proteins?

    <p>Golgi apparatus</p> Signup and view all the answers

    What is the main characteristic of lipid-anchored membrane proteins?

    <p>They are covalently attached to lipid chains.</p> Signup and view all the answers

    Which of the following proteins is an example of a GPI-linked protein?

    <p>N-CAM</p> Signup and view all the answers

    How do peripheral proteins typically attach to the membrane?

    <p>By electrostatic bonds with membrane lipids or interactions with other proteins.</p> Signup and view all the answers

    Which fatty acid is linked to protein kinases and growth hormone receptors as an anchor?

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

    What is a common function of G trimeric proteins?

    <p>Coupling between primary effectors and membrane-associated enzymes.</p> Signup and view all the answers

    What is a primary characteristic of transmembrane proteins?

    <p>They penetrate the hydrophobic interior of the lipid bilayer.</p> Signup and view all the answers

    Which of the following accurately describes the structure of transmembrane proteins?

    <p>They usually consist of coiled helices formed by nonpolar amino acids.</p> Signup and view all the answers

    What role do oligosaccharides play in many transmembrane proteins?

    <p>They are exposed on the surface and contribute to glycoprotein formation.</p> Signup and view all the answers

    In what form do sulfhydryl groups typically exist in the cytoplasmic domain of transmembrane proteins?

    <p>They are usually maintained in their reduced form.</p> Signup and view all the answers

    What type of structure do transmembrane proteins primarily form?

    <p>Beta-barrel structure</p> Signup and view all the answers

    How do some polypeptide chains traverse the lipid bilayer in a unique structure?

    <p>They roll into a cylindrical structure known as a beta barrel.</p> Signup and view all the answers

    Which amino acid side chains are predominantly found inside the barrel of transmembrane proteins?

    <p>Hydrophilic side chains</p> Signup and view all the answers

    In which type of membranes are beta-barrel proteins predominantly located?

    <p>Bacterial and mitochondrial membranes</p> Signup and view all the answers

    What is a significant example of a beta-barrel structure?

    <p>Porin proteins</p> Signup and view all the answers

    What is the role of integral monotopic proteins in relation to the lipid bilayer?

    <p>They are associated with the cytoplasmic half of the lipid bilayer.</p> Signup and view all the answers

    What is one function of membrane proteins related to solute transport?

    <p>Forming hydrophilic channels for specific solutes.</p> Signup and view all the answers

    Which function of membrane proteins involves interaction with the cytoskeleton?

    <p>Anchoring the membrane to macromolecules.</p> Signup and view all the answers

    What percentage of the mass of most plasma membranes do carbohydrates comprise?

    <p>5-10%</p> Signup and view all the answers

    What primarily constitutes the outer leaflet of lipid rafts?

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

    Which proteins are primarily concentrated in the inner leaflet of lipid rafts?

    <p>Src kinase and lipid-anchored proteins</p> Signup and view all the answers

    What are glycoproteins?

    <p>Membrane proteins linked to oligosaccharides.</p> Signup and view all the answers

    What role do lipid rafts play in cellular function?

    <p>They form signaling microdomains for certain receptors.</p> Signup and view all the answers

    Which of the following is NOT a function of membrane proteins?

    <p>Storing genetic information.</p> Signup and view all the answers

    In the context of lipid rafts, which lipid molecule tends to concentrate alongside cholesterol in the inner leaflet?

    <p>Glycerophospholipids with long saturated fatty acyl tails</p> Signup and view all the answers

    Which of the following is thought to stabilize lipid rafts?

    <p>Proteins that bind to carbohydrates in the trans-Golgi network</p> Signup and view all the answers

    What percentage of the mass of most plasma membranes is constituted by carbohydrates?

    <p>5-10%</p> Signup and view all the answers

    Which of the following describes glycoproteins?

    <p>Proteins linked to short chains of sugars</p> Signup and view all the answers

    Where is the carbohydrate layer, or glycocalyx, located?

    <p>On the outside of the plasma membrane</p> Signup and view all the answers

    Where are sugar residues added to glycosylated transmembrane proteins?

    <p>In the lumen of the ER and Golgi apparatus</p> Signup and view all the answers

    What is the primary role of glycolipids in the plasma membrane?

    <p>To form a sugar coating on the cell surface</p> Signup and view all the answers

    What role do carbohydrates play in the adhesion phenomena between cells?

    <p>They contribute to cell adhesion through specific molecules.</p> Signup and view all the answers

    Which of the following statements about the immunological reactions of carbohydrates is true?

    <p>They can act as antigens in blood group classification.</p> Signup and view all the answers

    How do carbohydrates influence the hydro-mineral environment of a cell?

    <p>They regulate osmotic pressure and maintain cell hydration.</p> Signup and view all the answers

    What is a physiological role of carbohydrates related to specific membrane receptors?

    <p>They participate in ligand recognition by specific membrane receptors.</p> Signup and view all the answers

    In what way do carbohydrates contribute to the insulation of certain axons?

    <p>Galactocerebroside acts as a glycolipid in the insulating sheath of myelin.</p> Signup and view all the answers

    What is one of the primary functions of biomembranes?

    <p>Compartmentalization of the cell contents</p> Signup and view all the answers

    Which characteristic of biomembranes contributes to their selective permeability?

    <p>Asymmetric organization</p> Signup and view all the answers

    What is a role of biomembranes in relation to cells?

    <p>Interacting between cells</p> Signup and view all the answers

    Which component is part of the structure of biomembranes?

    <p>Double layer of phospholipids</p> Signup and view all the answers

    Which process is NOT directly associated with the functioning of biomembranes?

    <p>Cell division</p> Signup and view all the answers

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