Acetylcholine Channel and Cell Membrane
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Questions and Answers

What type of channel protein allows for the selective passage of water while excluding other molecules?

  • Cholesterol pores
  • Carrier proteins
  • Aquaporin (correct)
  • Ion channels

    • Which part of the phospholipid bilayer shows affinity towards the aqueous environment?

  • Hydrophilic head (correct)
  • Cholesterol
  • Sphingolipid
  • Hydrophobic tail

    • Which type of transport does not require energy and relies on the concentration gradient?

  • Endocytosis
  • Active transport
  • Osmosis
  • Facilitated diffusion (correct)

    • What is the primary role of carrier proteins in cell membranes?

    <p>To facilitate the passage of substances through the lipid bilayer</p> Signup and view all the answers

    Which characteristic of the cell membrane contributes to its selective permeability?

    <p>The presence of both hydrophilic and hydrophobic regions</p> Signup and view all the answers

    What type of molecules are primarily found in nerve cell membranes, aiding in signaling?

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

    Which statement best describes the function of lipid bilayers in cell membranes?

    <p>They serve as a highly sensitive barrier with selective permeability.</p> Signup and view all the answers

    Which type of transport requires energy input through ATP to move substances against their concentration gradient?

    <p>Active transport</p> Signup and view all the answers

    What is the role of the Goldman equation in cell membrane study?

    <p>To calculate membrane potential</p> Signup and view all the answers

    What ions are involved in the calculation of the resting membrane potential?

    <p>Sodium (Na⁺), Potassium (K⁺), and Chloride (Cl⁻)</p> Signup and view all the answers

    Which value is derived from the Nernst potential of potassium (K)?

    <p>-94 mV</p> Signup and view all the answers

    What initiates the action potential in a nerve fiber?

    <p>A sudden change to a positive potential</p> Signup and view all the answers

    What is the resting stage of the action potential characterized by?

    <p>A stable negative membrane potential</p> Signup and view all the answers

    What happens to the membrane potential during an action potential?

    <p>It rapidly changes from negative to positive then back to negative</p> Signup and view all the answers

    How is the value of -90 mV for the resting membrane potential derived?

    <p>From the contribution of sodium, potassium, and chloride ions</p> Signup and view all the answers

    What is the significance of the action potential moving along the nerve fiber?

    <p>It allows for communication of nerve signals</p> Signup and view all the answers

    What is the rate of sodium conductance during the early portion of the action potential compared to potassium conductance?

    <p>It increases more than 1000-fold.</p> Signup and view all the answers

    What occurs to the inactivation gate of the voltage-gated sodium channel during repolarization?

    <p>It closes several 10,000ths of a second after the activation gate opens.</p> Signup and view all the answers

    How does the conductance of sodium compare to potassium during repolarization?

    <p>Potassium conductance is high and sodium conductance is virtually zero.</p> Signup and view all the answers

    What happens to the membrane potential after sodium channels begin to close?

    <p>It begins to return towards the resting membrane state.</p> Signup and view all the answers

    What role do potassium ions play during repolarization?

    <p>They exit the cell, contributing to the loss of positive charge.</p> Signup and view all the answers

    How does the timing of the inactivation gate closing compare to the activation gate during an action potential?

    <p>The activation gate opens before the inactivation gate closes.</p> Signup and view all the answers

    What is the consequence of the sodium channels closing while potassium channels begin to open?

    <p>Rapid loss of potassium ions occurs, causing membrane potential shifts.</p> Signup and view all the answers

    What ultimately happens to the inactivation gates when the membrane potential nears the resting state?

    <p>They return to their original state.</p> Signup and view all the answers

    How does concentration difference affect the net rate of diffusion?

    <p>It is directly proportional to the net rate of diffusion.</p> Signup and view all the answers

    Which of the following factors is NOT stated as affecting the net rate of diffusion?

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

    What does the term 'osmolarity' refer to?

    <p>The osmolar concentration expressed as osmoles per liter of solution.</p> Signup and view all the answers

    What determines the rate at which a substance diffuses inward through a membrane?

    <p>The concentration of molecules on the outside of the membrane.</p> Signup and view all the answers

    How does pressure difference contribute to diffusion?

    <p>It allows for greater collision of molecules with the membrane.</p> Signup and view all the answers

    In the context of the Nernst equation, what is a primary factor influencing the balance of univalent ions like sodium and potassium?

    <p>Electrical potential difference.</p> Signup and view all the answers

    Which of the following statements about factors affecting diffusion is true?

    <p>Concentration difference directly increases the rate of diffusion.</p> Signup and view all the answers

    How is the term 'osmolarity' defined in the provided content?

    <p>As the concentration of solutes expressed per liter.</p> Signup and view all the answers

    What distinguishes an isotonic solution from an isosmotic solution?

    <p>An isotonic solution has the same salt concentration as cells, while an isosmotic solution simply has equal molar concentrations of solutes.</p> Signup and view all the answers

    Why is normal saline considered isotonic while D-5-W is considered hypotonic?

    <p>Normal saline does not contribute to cell volume changes, whereas D-5-W leads to glucose entry into cells.</p> Signup and view all the answers

    What happens to glucose in a D-5-W solution when administered intravenously?

    <p>Glucose enters cells, causing water to follow and increasing cell volume.</p> Signup and view all the answers

    Which of the following statements about osmolarity and tonicity is true?

    <p>Hyperosmotic solutions are distinct from hypertonic solutions due to solute permeability.</p> Signup and view all the answers

    How does blood glucose homeostasis relate to D-5-W administration?

    <p>Administering D-5-W stimulates insulin release and enhances glucose uptake.</p> Signup and view all the answers

    What is the primary outcome of administering a D-5-W solution into a patient's bloodstream?

    <p>It leads to cell swelling as glucose is metabolized within the cells.</p> Signup and view all the answers

    Why can't isosmotic solutions be automatically assumed to be isotonic?

    <p>Cell membrane permeability to solutes affects the resulting tonicity.</p> Signup and view all the answers

    What is a key difference between the concepts of osmolarity and tonicity?

    <p>Osmolarity quantifies all solutes in a solution, while tonicity specifically evaluates the solute's effect on cell volume.</p> Signup and view all the answers

    Study Notes

    Acetylcholine Channel and Cell Membrane Structure

    • Cell membranes are composed of a phospholipid bilayer, featuring hydrophilic heads and hydrophobic tails.
    • Cholesterol and sphingolipids enhance membrane structure and fluidity, with sphingolipids prevalent in nerve cells.
    • Pores are cell membrane proteins forming open tubes, permitting selective passage of certain molecules based on diameter and electrical charge.

    Aquaporin and Carrier Proteins

    • Aquaporins are specialized protein pores functioning solely as water channels, allowing rapid water movement while excluding other substances.
    • Carrier proteins facilitate active transport, shifting substances through the lipid bilayer either by diffusion or against electrochemical gradients.
    • Transport mechanisms include facilitated diffusion (energy-free) and active transport (requires ATP).

    Factors Affecting Diffusion

    • Concentration Difference: The net rate of diffusion correlates with the difference in concentration between intra- and extracellular environments.
    • Pressure Difference: Movement from high to low pressure enhances diffusion, driven by the collision of molecules across a surface.
    • Osmolarity is expressed as osmoles per liter and indicates the concentration of solutes affecting membrane dynamics.

    Membrane Potential and Action Potentials

    • The Goldman equation calculates membrane potential involving sodium (Na+), potassium (K+), and chloride (Cl−) ions.
    • Action potentials are rapid changes in membrane potential facilitating nerve signal transmission, transitioning from a resting state to positive then returning quickly to negative.
    • The resting membrane potential is approximately -90mV, derived from the Nernst potentials of K+ (-94mV) and Na+ (+61mV).

    Stages of Action Potential

    • Resting Stage: The membrane is stable until stimulated.
    • Depolarization: Sodium channels open, allowing Na+ influx, reversing membrane polarity.
    • Repolarization: Sodium channels close, potassium channels open, leading to K+ efflux and returning membrane potential toward resting levels.

    Inactivation Gates and Ion Roles

    • Inactivation gates on sodium channels close shortly after activation, preventing further Na+ entry during repolarization.
    • During the action potential, sodium conductance increases dramatically, leading to depolarization.
    • After the peak of action potential, potassium conductance rises, facilitating rapid repolarization.

    Osmolarity and Tonicity in IV Solutions

    • Isotonic solutions have the same solute concentration as cellular fluids, preventing net water movement into or out of cells.
    • Examples include normal saline (0.9% NaCl) being isotonic while D-5-W (5% glucose) becomes hypotonic after glucose enters cells, causing water to follow osmotically.
    • Isosmotic solutions are not always isotonic due to cellular uptake of solutes, affecting net water movement and cell volume.

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    Membrane Transport, Nerve Potential, Action Potential Lecture Notes (PHYSIO) PDF

    Description

    Explore the key components and functions of acetylcholine channels in relation to cell membrane proteins. This quiz covers various lipids such as cholesterol and sphingolipids and their roles in forming pores. Test your knowledge on how these elements contribute to membrane selectivity and functionality.

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