Cell Structure and Functions: Membrane Transport
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Questions and Answers

Which process involves the movement of more than one substance at a time, with substances being moved in the same direction?

  • Exocytosis
  • Phagocytosis
  • Symport (correct)
  • Pinocytosis
  • What type of transport across membranes involves the ejection of substances 'out of the cell'?

  • Exocytosis (correct)
  • Receptor-mediated endocytosis
  • Phagocytosis
  • Endocytosis
  • Which example best illustrates 'cell drinking'?

  • WBC engulfing bacteria
  • Phagocytosis by intestinal cells
  • Transport of Na+/Glucose
  • Pinocytosis by intestinal cells (correct)
  • The concentration of specific substances that bind to receptor proteins is a characteristic of which type of endocytosis?

    <p>Receptor-mediated endocytosis</p> Signup and view all the answers

    In which process are large or solid materials engulfed by cells?

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

    What type of transport moves fluid and large particles across membranes in vesicles?

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

    What is the function of the cell membrane in regards to transport?

    <p>Selectively permitting some substances to enter or exit the cell</p> Signup and view all the answers

    Why does passive transport not require ATP energy?

    <p>Passive transport relies on the kinetic energy of molecules</p> Signup and view all the answers

    What is the term used to describe the fluid outside of cells that contains nutrients like amino acids and sugars?

    <p>Interstitial fluid</p> Signup and view all the answers

    When does diffusion occur?

    <p>When solute concentration is higher inside the cell</p> Signup and view all the answers

    What is the primary difference between facilitated diffusion and simple diffusion?

    <p>Facilitated diffusion involves carrier proteins, while simple diffusion does not</p> Signup and view all the answers

    What is the significance of a concentration gradient in the context of membrane transport?

    <p>A concentration gradient drives diffusion and other forms of passive transport</p> Signup and view all the answers

    Which process involves the diffusion of H2O from high to low concentration?

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

    Which type of proteins form passageways through the plasma membrane for specific ions or molecules?

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

    What is the main difference between isotonic and hypertonic solutions?

    <p>Hypertonic has higher solute concentration than isotonic</p> Signup and view all the answers

    Which type of transport requires energy and moves molecules against the concentration gradient?

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

    What do carrier proteins do to assist in the transport of molecules across the membrane?

    <p>Bind to molecules, change shape, and ferry them across the membrane</p> Signup and view all the answers

    In which type of transport does ATP directly drive the process?

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

    Study Notes

    Cell Structure

    • A cell has three basic parts: the plasma membrane, the cytoplasm, and the genetic material (DNA or RNA)
    • The plasma membrane regulates what enters and leaves the cell
    • The cytoplasm is the jelly-like substance inside the cell where metabolic reactions occur
    • The genetic material contains the cell's instructions for growth, reproduction, and response to stimuli

    Phospholipids in a Watery Environment

    • Phospholipids organize into a bilayer in a watery environment due to their hydrophobic tails and hydrophilic heads
    • The tails face inward, away from water, and the heads face outward, interacting with water

    Membrane Transport

    • Membrane transport refers to the movement of substances (solutes, ions, and water) in and out of the cell
    • Two factors involved: permeability and size of solutes or substances
    • Interstitial fluid is the fluid outside cells, rich in nutrients, sugars, fatty acids, vitamins, hormones, salts, and wastes

    Selective Permeability

    • The plasma membrane allows only certain substances to enter the cell
    • Nutrients enter, and wastes leave the cell through passive or active transport mechanisms

    Passive Transport

    • No energy (ATP) is needed
    • Molecules move down their concentration gradient from high to low concentration
    • Types of passive transport: diffusion, osmosis, and facilitated diffusion

    Concentration Gradient

    • A concentration gradient exists when the solute concentration in a solvent is greater at one point than at another
    • The concentration gradient is calculated as the concentration difference between two points divided by the distance between them

    Diffusion

    • The movement of solutes from an area of higher concentration to an area of lower concentration
    • Example: a salt crystal placed in a beaker of water, where salt ions move into the water, eventually reaching equilibrium

    Facilitated Diffusion

    • Transport proteins (carrier or channel proteins) assist molecules across the membrane
    • Examples: glucose, amino acids, H2O, and ions
    • Channel proteins form passageways through the plasma membrane, allowing specific ions or molecules to enter or exit the cell
    • Carrier proteins bind to molecules, change shape, and ferry them across the membrane

    Osmosis

    • Refers to the diffusion of water from high to low concentration
    • Aquaporins are channel proteins for water passage
    • Tonicity refers to the ability of a solution to change the shape or tone of cells by changing water volume

    Active Transport

    • Energy (ATP) is needed to move molecules against their concentration gradient from low to high concentration
    • Types of active transport: primary and secondary active transport

    Primary Active Transport

    • Directly uses ATP to drive transport
    • Examples: Ca2+ pump, H+ pump, and Na+-K+ pump
    • The sodium-potassium pump is an example of primary active transport

    Secondary Active Transport

    • Moves more than one substance at a time
    • Types: symport (2 substances moved in the same direction) and antiport (2 substances moved in opposite directions)
    • Examples: cotransport of sugars, amino acids, and ions

    Vesicular Transport

    • Fluid and large particles are transported across membranes in vesicles (sacs)
    • Types: exocytosis (eject substances out of the cell) and endocytosis (ingest substances into the cell)

    Endocytosis

    • Types: phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis
    • Examples: white blood cells engulfing bacteria, intestinal cells ingesting fluid with dissolved molecules, and concentration of specific substances (ligands) that bind to receptor proteins

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    Test your knowledge on the functions of basic parts of a cell, reasons for phospholipid bilayer organization, and mechanisms of membrane transport for substances in and out of the cell.

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