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BIO 102: Transport across the Membrane
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BIO 102: Transport across the Membrane

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Questions and Answers

What is the primary difference between facilitated diffusion and active transport?

  • The direction of solute movement
  • The type of transport proteins used
  • The presence of a concentration gradient
  • The requirement of energy input (correct)
  • What is the energy source used by the Sodium-Potassium pump?

  • Glucose
  • Oxygen
  • Sodium ions
  • ATP (correct)
  • What is the purpose of the Sodium-Potassium pump in animal cells?

  • To maintain pH balance
  • To regulate temperature
  • To synthesize ATP
  • To maintain ion gradients for nerve and muscle function (correct)
  • What is the direction of solute movement in active transport?

    <p>Against the concentration gradient</p> Signup and view all the answers

    What is the ratio of sodium ions expelled to potassium ions admitted by the Sodium-Potassium pump?

    <p>3:2</p> Signup and view all the answers

    What is the result of active transport in cells?

    <p>Creation of a concentration gradient</p> Signup and view all the answers

    Why is it essential to maintain high concentrations of potassium and low concentrations of sodium in animal cells?

    <p>For nerve and muscle function</p> Signup and view all the answers

    What is the primary function of transport proteins in active transport?

    <p>To move solutes against their concentration gradient</p> Signup and view all the answers

    What is the net transfer of charge with each 'crank' of the sodium-potassium pump?

    <p>One positive charge from the cytoplasm to the extracellular fluid</p> Signup and view all the answers

    What is the main function of electrogenic pumps?

    <p>To generate voltage across a membrane</p> Signup and view all the answers

    What is the primary use of proton gradients in the cell?

    <p>For ATP synthesis during cellular respiration</p> Signup and view all the answers

    What is the mechanism by which a co-transporter couples the transport of two solutes?

    <p>The downhill diffusion of one solute drives the uphill transport of another solute</p> Signup and view all the answers

    What is the role of the proton pump in co-transport?

    <p>To maintain the electrochemical gradient of H+</p> Signup and view all the answers

    What is the direction of H+ transport during co-transport?

    <p>Down its concentration gradient from the extracellular fluid to the cell</p> Signup and view all the answers

    What is the purpose of H+ /sucrose co-transport in plants?

    <p>To load sucrose into cells in the veins of leaves</p> Signup and view all the answers

    What is the characteristic of an electrogenic pump?

    <p>It generates voltage across a membrane</p> Signup and view all the answers

    What is the primary function of exocytosis in cells?

    <p>To export products out of the cell</p> Signup and view all the answers

    Which type of molecules generally cross the cell membrane by bulk transport?

    <p>Large molecules like proteins and polysaccharides</p> Signup and view all the answers

    What is the process by which the cell membrane engulfs fluids and large molecules to bring them into the cell?

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

    Which of the following requires energy?

    <p>Exocytosis and endocytosis</p> Signup and view all the answers

    What is the role of microtubules in exocytosis?

    <p>To provide a pathway for vesicles to move to the plasma membrane</p> Signup and view all the answers

    What is the result of the fusion of vesicle and plasma membranes during exocytosis?

    <p>The vesicle membrane becomes part of the plasma membrane</p> Signup and view all the answers

    Which type of cells use exocytosis to export products?

    <p>All of the above</p> Signup and view all the answers

    What is the result of the indentation of the cell membrane during endocytosis?

    <p>A 'bubble' of membrane closes in on itself</p> Signup and view all the answers

    Study Notes

    Transport across the Membrane

    • Despite the help of transport proteins, facilitated diffusion is considered passive transport because the solute is moving down its concentration gradient, requiring no energy.
    • Active transport, on the other hand, uses a transport protein to move a substance against its concentration gradient, requiring energy input, often from ATP.

    Active Transport

    • One active transport system is the Sodium-Potassium pump, which uses ATP to expel 3 Na+ for every 2 K+ it admits, contributing to the membrane potential.
    • This process is essential for nerve and muscle function in animals, where high concentrations of potassium (K+) and low concentrations of sodium (Na+) are necessary.

    Electrogenic Pumps

    • The sodium-potassium pump is an electrogenic pump, generating voltage across a membrane.
    • In plants, fungi, and bacteria, the main electrogenic pump is a proton pump, actively transporting protons (H+) out of the cell.

    Co-transport (2ry Active Transport)

    • Co-transport couples the "downhill" diffusion of a solute to the "uphill" transport of a second substance against its own concentration gradient.
    • For example, in plants, the gradient of H+ generated by ATP-powered proton pumps drives the active transport of amino acids, sugars, and other nutrients into the cell.

    Bulk Transport

    • Bulk transport occurs by Exocytosis and Endocytosis, allowing large molecules and particles to cross the plasma membrane.
    • Like active transport, these processes require energy.

    Exocytosis

    • Exocytosis is the process by which the cell secretes certain molecules by the fusion of vesicles with the plasma membrane.
    • Vesicles that have budded from the Golgi apparatus move along microtubules to the plasma membrane, fuse with the membrane, and release their contents outside the cell.

    Endocytosis

    • Endocytosis is the process by which the cell engulfs fluids and large molecules to bring them into the cell.
    • The cell membrane indents, and a "bubble" of membrane closes in on itself, forming a vesicle.

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    Description

    This quiz covers transport across the membrane, including passive and active transport, and the role of transport proteins in facilitating the movement of solutes.

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