Cell Membrane Functions
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Questions and Answers

What is the primary factor that influences the rate of diffusion, according to Fick's Law?

  • Surface area of the membrane
  • Molecular weight of the substance
  • Lipid solubility of the substance
  • Concentration gradient of the substance (correct)

    • Which of the following is NOT a characteristic of unassisted membrane transport diffusion?

  • It only occurs if the substance can cross the membrane
  • It is a passive mechanism
  • It always moves from an area of high to low concentration
  • It requires energy input (correct)

    • What type of hormones can move into cells passively?

  • Amino acid hormones
  • Peptide hormones
  • Protein hormones
  • Steroid hormones (correct)

    • What is the term for the movement of water down its own concentration gradient through a semipermeable membrane?

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

    What is the term for the difference in concentration of non-penetrating solutes between two solutions?

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

    What is the formula for the rate of diffusion, according to Fick's Law?

    <p>Rate = (SA x CG)/ TW</p> Signup and view all the answers

    What happens to a cell in a hypotonic solution?

    <p>It bursts</p> Signup and view all the answers

    What is the function of membrane-spanning proteins in carrier-mediated transport?

    <p>To bind and transport specific substances</p> Signup and view all the answers

    What is the maximum rate of transport by a carrier protein?

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

    Which type of transport involves the movement of a substance from high to low concentration?

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

    What happens to the carrier protein after the solute molecule binds to it in facilitated diffusion?

    <p>It changes conformation to release the solute</p> Signup and view all the answers

    What is the purpose of GLUT4 in adipose muscles?

    <p>To facilitate glucose uptake</p> Signup and view all the answers

    What is the primary function of the cell membrane as a physical barrier?

    <p>To separate the cell from its environment and prevent toxic waste buildup</p> Signup and view all the answers

    What is the main characteristic of the fluid mosaic model of the cell membrane?

    <p>A fluid structure with a dynamic arrangement of proteins and lipids</p> Signup and view all the answers

    What is the function of intrinsic proteins in the cell membrane?

    <p>To span the entire width of the membrane and function as self-identity markers</p> Signup and view all the answers

    What is the purpose of cholesterol in the cell membrane?

    <p>To provide fluidity and stability to the membrane</p> Signup and view all the answers

    What is the function of glycoproteins in the cell membrane?

    <p>To function as self-identity markers and help with cell differentiation</p> Signup and view all the answers

    What type of protein is aquaporin?

    <p>Water channel</p> Signup and view all the answers

    What is the function of cell adhesion molecules (CAMs) in the cell membrane?

    <p>To help with the adhesion of cells to each other</p> Signup and view all the answers

    What is the term for the entire structure of cells, tissues, organs, and systems that make up an organism?

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

    What is the term for the process of cells working together to provide signals on what needs to happen?

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

    What is the function of the phospholipid bilayer in the cell membrane?

    <p>To form a barrier that separates the cell from its environment</p> Signup and view all the answers

    What is the effect of acetylcholine binding to its receptor on the voltage-gated ion channel?

    <p>It opens the channel, allowing Na+ flow in.</p> Signup and view all the answers

    What is the purpose of the Na+/K+ ATPase pump in generating the resting membrane potential?

    <p>To pump 3 Na+ out and 2 K+ in.</p> Signup and view all the answers

    What is the equilibrium potential of K+ (Ek+)?

    <p>-90 mV</p> Signup and view all the answers

    What is the general mechanism of second messenger pathways?

    <p>The first messenger binds to a receptor, releasing a second messenger, which then relays the signal.</p> Signup and view all the answers

    What is the primary mechanism by which sodium ions are transported out of the blood?

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

    What is the purpose of leak channels for Na and K ions?

    <p>To passively allow diffusion down their concentration gradients.</p> Signup and view all the answers

    Which type of transport involves the movement of molecules down their concentration gradient?

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

    Why is the equilibrium potential for Na+ lower than for K+?

    <p>Because the concentration gradient for Na+ is smaller than for K+.</p> Signup and view all the answers

    What is the primary function of Na+/K+ ATPase in the kidney?

    <p>To regulate the concentration of sodium ions outside the cell</p> Signup and view all the answers

    Which type of vesicular transport involves the non-selective uptake of extracellular fluid?

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

    What is the primary function of exocytosis in the cell?

    <p>To secrete neurotransmitters and hormones</p> Signup and view all the answers

    Which type of cell communication involves the direct contact of plasma membranes between cells?

    <p>Juxtacrine signaling</p> Signup and view all the answers

    What is the primary function of lipid-soluble chemical messengers in signal transduction?

    <p>To cross the plasma membrane and affect gene transcription</p> Signup and view all the answers

    What is the primary function of ion channels in the cell?

    <p>To allow ions to move into the cell and affect physiological responses</p> Signup and view all the answers

    Which type of ion channel is always open and allows for the leakage of ions into and out of the cell?

    <p>Leak channel</p> Signup and view all the answers

    What is the primary function of ligand-gated ion channels in the cell?

    <p>To open and close in response to stimuli</p> Signup and view all the answers

    Study Notes

    Passive Transport

    • Passive transport occurs without energy input, allowing substances to move from high to low concentration
    • Types of passive transport:
      • Diffusion: movement of substances from high to low concentration
      • Osmosis: movement of water molecules from high to low concentration

    Facilitated Diffusion

    • Facilitated diffusion is a type of carrier-mediated transport
    • Carrier proteins bind to specific substances and transport them across the membrane
    • Characteristics:
      • Specificity: each carrier protein binds to specific substances
      • Saturation: finite number of carrier proteins, leading to saturation
      • Competition: multiple substances competing for same carrier protein
    • Examples:
      • GLUT4: facilitates glucose transport into adipose and muscle cells
      • Insulin stimulates GLUT4 insertion into cell membrane

    Active Transport

    • Active transport moves substances from low to high concentration, requiring energy input
    • Examples:
      • Iodine uptake in thyroid gland cells
      • Sodium-potassium pump (Na+/K+ ATPase) maintains ion balance

    Cell Membrane Structure

    • Fluid mosaic model: flexible and dynamic structure with integral and peripheral proteins
    • Components:
      • Phospholipids: amphipathic molecules forming bilateral layer
      • Cholesterol: maintains fluidity and stability
      • Carbohydrates: attached to lipids or proteins, functioning as identity markers
    • Functions:
      • Physical barrier
      • Homeostasis maintenance
      • Mechanical barrier
      • Adhesion between cells
      • Cell signaling

    Membrane Proteins

    • Types:
      • Intrinsic (integral): spanning the membrane
      • Extrinsic (peripheral): attached to one side of the membrane
    • Functions:
      • Aquaporins: water channels
      • Ion channels: selective ion transport
      • Carrier molecules: facilitated diffusion
      • Receptors: binding specific molecules
      • Enzymes: performing physiological activities
      • Cell adhesion molecules (CAMs): adhering cells together

    Cell-Cell Adhesions

    • Cell-cell adhesions form tissues, organs, and systems
    • Extracellular matrix (ECM) components:
      • Proteins
      • Polysaccharides
      • GAGs
    • Functions:
      • Adhesion
      • Signaling
      • Mechanical support

    Second Messenger Pathways

    • Second messenger relays signals inside the cell
    • Amplifies initial response through a signaling cascade
    • Two major pathways:
      • Cyclic AMP
      • Ca2+/DAG

    Membrane Potential

    • Plasma membrane is polarized electrically, with a potential difference across the membrane
    • Generation of RMP (-70mV) due to unequal distribution of Na+, K+, and anions
    • Membrane potential is the capacity to do work, measured in millivolts (mV)

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    Description

    Learn about the crucial functions of the cell membrane, including its role as a physical barrier, maintaining homeostasis, and facilitating exchange of nutrients and wastes. Discover how it responds to environmental changes and signals, and how it knows when to produce an enzyme.

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