Cell Membrane
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Cell Membrane

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Questions and Answers

What effect do calcium ions have on sodium channel activation gates?

  • They make it easier for sodium channels to open.
  • They stabilize the activation gates, making it harder for them to open. (correct)
  • They enhance the excitability of the membrane.
  • They have no effect on sodium channel activation.

    • How does a high extracellular fluid calcium ion concentration affect sodium ion permeability?

  • It fluctuates sodium ion permeability based on other ions present.
  • It increases sodium ion permeability.
  • It reduces sodium ion permeability. (correct)
  • It has no impact on sodium ion permeability.

    • What is the safety factor in the context of nerve impulses?

  • The ratio of nerve impulse frequency to action potential strength.
  • The time taken for a nerve impulse to travel across a synapse.
  • The ratio of action potential strength to excitability threshold. (correct)
  • The measure of the voltage across the membrane during rest.

    • What is the primary mechanism of action of local anesthetics on sodium channels?

    <p>They slow down the activation gates' opening process.</p> Signup and view all the answers

    What occurs when the safety factor is reduced below 1.0?

    <p>Nerve impulses fail to pass along anesthetized nerves.</p> Signup and view all the answers

    Which type of protein is solely responsible for diffusion?

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

    What characterizes facilitated diffusion compared to simple diffusion?

    <p>Involves carrier proteins</p> Signup and view all the answers

    How do carrier proteins primarily transport substances?

    <p>By undergoing conformational changes</p> Signup and view all the answers

    Which process requires moving water molecules through specific channels in the membrane?

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

    What distinguishes active transport from passive transport?

    <p>It requires energy from ATP</p> Signup and view all the answers

    Which of the following describes the motion involved in diffusion?

    <p>Based on normal kinetic motion of matter</p> Signup and view all the answers

    Aquaporins are essential for which mechanism of transport?

    <p>Facilitated diffusion of water</p> Signup and view all the answers

    Which term refers to the total concentration of solute particles in a solution?

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

    What energy source is primarily used by the sodium-potassium pump?

    <p>Breakdown of ATP</p> Signup and view all the answers

    What is the main function of the sodium-potassium pump?

    <p>Maintaining sodium outside and potassium inside the cell</p> Signup and view all the answers

    How many sodium ions does the sodium-potassium pump move outside the cell for each cycle?

    <p>3 sodium ions</p> Signup and view all the answers

    What is the role of the alpha subunit in the sodium-potassium pump?

    <p>Serving as the functional unit of the pump</p> Signup and view all the answers

    What is the concentration ratio of calcium ions inside the cell compared to outside?

    <p>1:10,000</p> Signup and view all the answers

    What type of transport process does the sodium-potassium pump utilize?

    <p>Primary active transport</p> Signup and view all the answers

    What happens to the electrical potential inside the membrane as a result of the sodium-potassium pump's activity?

    <p>It becomes more negative</p> Signup and view all the answers

    Which of the following describes the calcium pump's main function?

    <p>Pumping calcium outside of the cell</p> Signup and view all the answers

    Which components are involved in the sodium-potassium pump binding process?

    <p>3 binding units for Na+ and 2 for K</p> Signup and view all the answers

    Which organelles are examples of where calcium pumps operate?

    <p>Sarcoplasmic reticulum and mitochondria</p> Signup and view all the answers

    What happens when the inside of the cell membrane becomes positively charged?

    <p>Potassium gates open</p> Signup and view all the answers

    What initiates the opening or closing of a gated channel?

    <p>Chemical binding of a ligand</p> Signup and view all the answers

    How wide is a typical sodium channel?

    <p>0.3 to 0.5 nanometers</p> Signup and view all the answers

    What role do amino acids play in sodium channels?

    <p>They are negatively charged and attract sodium ions</p> Signup and view all the answers

    At what condition do gated channels typically exhibit variability in their state?

    <p>At different voltage potentials</p> Signup and view all the answers

    What is the primary function of ligand-gated channels?

    <p>Control ion flow in response to ligands</p> Signup and view all the answers

    Which of the following is an example of a ligand that can affect gated channels?

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

    What occurs during the closed state of a sodium channel?

    <p>Sodium ions are blocked from entering</p> Signup and view all the answers

    What characterizes the open state of a gated channel?

    <p>Ions can move freely through the channel</p> Signup and view all the answers

    What is a key feature of the potassium gates in relation to membrane potential?

    <p>They open when the inside of the cell becomes positively charged</p> Signup and view all the answers

    What is the primary function of co-transport in cellular transport mechanisms?

    <p>To couple the transport of two substances together</p> Signup and view all the answers

    Which of the following best describes sodium-hydrogen counter-transport?

    <p>It exchanges hydrogen ions to regulate blood pH</p> Signup and view all the answers

    Where is sodium-glucose co-transport primarily found?

    <p>In the epithelial cells of the intestine</p> Signup and view all the answers

    What stimulates the transport of sodium ions and the co-transported substance in co-transport mechanisms?

    <p>Concentration gradient of the sodium ion</p> Signup and view all the answers

    What role does the carrier protein serve in co-transport mechanisms?

    <p>It acts as an attachment point for transported substances</p> Signup and view all the answers

    Which of the following ions is exchanged during the sodium-hydrogen counter-transport?

    <p>Hydrogen ions</p> Signup and view all the answers

    In which part of the human body does sodium-glucose co-transport particularly occur?

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

    What maintains the acidity of urine through hydrogen ion exchange?

    <p>Sodium-hydrogen counter-transport</p> Signup and view all the answers

    What is a key mechanism by which cells transport glucose against its concentration gradient?

    <p>Co-transport with sodium ions</p> Signup and view all the answers

    What is a consequence of sodium-glucose co-transport mechanisms in the kidneys?

    <p>Enhanced absorption of glucose</p> Signup and view all the answers

    Study Notes

    Cell Membrane

    • Consists of a phospholipid bilayer with embedded proteins.
    • It is selectively permeable, controlling what enters and exits the cell.

    Cell Membrane Transport

    • The movement of substances across the cell membrane.
    • Two main types: diffusion and active transport.

    Diffusion

    • The movement of molecules from an area of high concentration to an area of low concentration.
    • Does not require energy.
    • Two types: simple diffusion and facilitated diffusion.

    Simple Diffusion

    • The movement of molecules across the cell membrane through intermolecular spaces or with the help of carrier proteins.
    • Its movement is based on the kinetic motion of molecules.

    Facilitated Diffusion

    • The movement of molecules across the cell membrane with the help of carrier proteins.
    • Carrier proteins bind to the molecules and facilitate their movement across the membrane.
    • Does not require energy.

    Aquaporins

    • Water channel proteins that facilitate the movement of water across the cell membrane.
    • They allow for rapid water movement.
    • Important for maintaining cell hydration.

    Osmosis

    • The movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.

    Osmolality

    • The concentration of dissolved particles in a solution.
    • It is expressed in osmoles per kilogram of solvent.

    Osmolarity

    • The concentration of dissolved particles in a solution.
    • It is expressed in osmoles per liter of solution.

    Active Transport

    • The movement of molecules across the cell membrane against their concentration gradient.
    • Requires energy.

    Primary Active Transport

    • The energy for transport comes directly from the breakdown of ATP.
    • Examples include the sodium-potassium pump and the calcium pump.

    Sodium-Potassium Pump

    • Pumps sodium ions out of the cell and potassium ions into the cell.
    • Maintains the electrochemical gradient across the cell membrane.
    • Necessary for nerve and muscle fiber function.

    Calcium Pump

    • Pumps calcium ions out of the cell.
    • Important for maintaining low intracellular calcium concentration.
    • Plays a crucial role in muscle contraction and other cellular processes.

    Secondary Active Transport

    • The energy for transport is derived indirectly from the movement of another substance down its concentration gradient.
    • Two types: co-transport and counter-transport.

    Co-Transport

    • Two molecules move in the same direction across the cell membrane.
    • One molecule's concentration gradient drives the movement of the other.
    • Example: glucose-sodium co-transport in the small intestine.

    Counter-Transport

    • Two molecules move in opposite directions across the cell membrane.
    • One molecule's concentration gradient drives the movement of the other.
    • Example: sodium-hydrogen counter-transport in the kidney tubules.

    Voltage-Gated Channels

    • Channel proteins that open or close in response to changes in the membrane potential.
    • Important for generating and transmitting nerve impulses.
    • Examples: sodium channels and potassium channels.

    Sodium Channels

    • Allow sodium ions to flow into the cell.
    • Open when the membrane potential depolarizes.

    Potassium Channels

    • Allow potassium ions to flow out of the cell.
    • Open when the membrane potential repolarizes.

    Ligand-Gated Channels

    • Channel proteins that open or close in response to the binding of a specific ligand.
    • Examples: acetylcholine receptor channels.

    Membrane Stabilizers

    • Substances that decrease membrane excitability by decreasing the permeability of the membrane to sodium ions.
    • Examples: calcium ions.

    Local Anesthetics

    • Substances that block the activation gates of sodium channels, reducing membrane excitability.
    • Examples: lidocaine, procaine.

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    Related Documents

    PHYSIO_LC3_TRANSPORT OF SUBSTANCES THROUGH CELL MEMBRANES.pdf

    Description

    Test your knowledge on cell membrane structure and transport mechanisms. This quiz covers concepts such as diffusion, facilitated diffusion, and the role of aquaporins. Understand how substances move across the cell membrane effectively.

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