Membrane Transport Quiz
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Questions and Answers

Which of the following best describes the energy requirements for transporting an uncharged molecule against its concentration gradient?

  • Only occurs if the molecule is transported via channels.
  • Requires energy input due to the movement against the concentration gradient. (correct)
  • Is solely dependent on the temperature of the environment.
  • Requires no energy input because the molecule is uncharged.

    • In the context of cellular transport, what is the fundamental difference between active and passive transport?

  • Active transport uses channels, while passive transport uses carriers.
  • Active transport requires energy input, while passive transport does not (though energy is required to establish the gradient). (correct)
  • Active transport moves substances down the electrochemical gradient, while passive transport moves substances against it.
  • Passive transport is facilitated by ATPases, while active transport relies on light energy.

    • How is the sodium/potassium pump categorized in terms of energy coupling?

  • Voltage-gated
  • ATPase (correct)
  • Light-driven
  • Redox-driven

    • Which of the following transport mechanisms is LEAST likely to be involved in active transport?

    <p>Channels (A)</p> Signup and view all the answers

    Considering the relationship between active and passive transport, what is the most accurate statement?

    <p>Active transport is a prerequisite for passive transport because it establishes the electrochemical gradient. (D)</p> Signup and view all the answers

    An uncharged molecule is transported across a membrane. What primarily determines its movement?

    <p>The chemical gradient of the molecule. (D)</p> Signup and view all the answers

    A cation is being transported across a cell membrane. Which factor would increase the rate of its transport into the cell?

    <p>Both A and B. (B)</p> Signup and view all the answers

    In Case 3, an anion's net driving force depends on the size between chemical and electrical gradients. If the anion's chemical gradient directs it out of the cell, but the electrical gradient drives it into the cell, under what condition will the anion move into the cell?

    <p>When the electrical gradient is stronger than the chemical gradient. (A)</p> Signup and view all the answers

    Consider an anion with a higher concentration outside the cell and a positive membrane potential (outside is positive). What must be true for the anion to move out of the cell?

    <p>The chemical gradient effect is greater than the electrical gradient. (A)</p> Signup and view all the answers

    Which of the following scenarios would result in the smallest net driving force on a charged ion?

    <p>Small chemical gradient and small electrical gradient in <em>opposite</em> directions. (C)</p> Signup and view all the answers

    A cell needs to transport potassium ions (K+) across its membrane. Considering both chemical and electrical gradients, which statement best describes the challenge the cell faces?

    <p>The cell must utilize transport proteins to facilitate the movement of potassium ions across the hydrophobic membrane, while also accounting for the influence of both concentration and charge differences. (C)</p> Signup and view all the answers

    Which of the following characteristics of transport proteins is LEAST likely to contribute to the 'controlled' interaction of a cell with its environment?

    <p>Their inherent property of allowing all molecules to pass freely and equally. (C)</p> Signup and view all the answers

    If a cell membrane suddenly became freely permeable to all ions, which of the following would most likely occur?

    <p>The cell would rapidly lose its ability to maintain distinct internal and external environments, disrupting essential functions. (A)</p> Signup and view all the answers

    In a scenario where the concentration of chloride ions (Cl-) is higher inside a cell compared to the outside, and assuming there's a negative electrical potential inside the cell, what would be the likely movement of chloride ions?

    <p>Chloride ions would move out of the cell due to chemical gradient, but the movement would be restricted by electrical gradient. (A)</p> Signup and view all the answers

    A researcher discovers a new transport protein that significantly increases the rate of glucose transport into a cell, but only when the cell is actively performing aerobic respiration. Which property is this transport protein most likely to possess?

    <p>The protein directly couples ATP hydrolysis to glucose transport. (B)</p> Signup and view all the answers

    In the context of cellular membrane transport, what is the key difference between active and passive transport?

    <p>Active transport requires energy input to move substances against the electrochemical gradient, while passive transport moves substances down the electrochemical gradient without energy input. (B)</p> Signup and view all the answers

    If a cell needs to transport a solute against its electrochemical gradient, which type of transport mechanism is required?

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

    What is the primary role of pumps in establishing electrochemical gradients across cellular membranes?

    <p>To establish ion concentration differences that drive other transport processes. (C)</p> Signup and view all the answers

    Which of the following best describes the 'gating' mechanism of ion channels?

    <p>The ability of the channel to open and close in response to specific stimuli. (B)</p> Signup and view all the answers

    During a patch-clamp experiment, what is the function of the suction pipette?

    <p>To isolate and form a tight seal with a small area of the cell membrane containing one or more ion channels. (C)</p> Signup and view all the answers

    Which of the following best describes the primary role of bacteriorhodopsin?

    <p>To use light energy to create a proton gradient. (B)</p> Signup and view all the answers

    How do pumps contribute to establishing electrochemical gradients?

    <p>By actively transporting ions against their concentration gradients, using energy. (D)</p> Signup and view all the answers

    In co-transport systems, what distinguishes a symporter from an antiporter?

    <p>Symporters move the driver ion and substrate in the same direction, while antiporters move them in opposite directions. (C)</p> Signup and view all the answers

    The salt bush (Atriplex) uses salt bladders to remove excess Na+ from its cells. Which transport system is most likely involved in this process?

    <p>A Na+/H+ antiporter. (A)</p> Signup and view all the answers

    How do transport proteins facilitate passive transport?

    <p>By providing a channel or undergoing conformational changes to allow solutes to move down their electrochemical gradients. (C)</p> Signup and view all the answers

    What is the primary difference between channels and carriers in passive transport?

    <p>Channels provide an aqueous pore, while carriers undergo conformational changes upon solute binding. (A)</p> Signup and view all the answers

    A cell needs to import glucose against its concentration gradient. Which mechanism would it most likely utilize?

    <p>Co-transport with an ion moving down its electrochemical gradient. (C)</p> Signup and view all the answers

    Why do some potassium (K+) channels exhibit a 100-fold higher permeability for K+ than for sodium (Na+)?

    <p>Because of specific structural features in the channel that precisely fit K+ ions, optimizing their passage. (A)</p> Signup and view all the answers

    Flashcards

    Membrane Transport

    The process of moving molecules across biological membranes.

    Transport Proteins

    Proteins that facilitate the movement of substances across a cell membrane.

    Facilitated Diffusion

    A type of passive transport that uses transport proteins to move molecules across membranes.

    Electrochemical Gradient

    The net driving force for moving molecules, combining chemical and electrical gradients.

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    Permeability

    The ability of a membrane to allow substances to pass through it.

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    Chemical Gradient

    The concentration difference of a substance across a membrane.

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    Electrical Gradient

    The difference in charge across a membrane that influences ion movement.

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    Net Driving Force

    The overall force moving ions, based on chemical and electrical gradients.

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    Cation

    A positively charged ion that seeks to move towards negatively charged areas.

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    Anion

    A negatively charged ion that is influenced by chemical and electrical forces.

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    Energy Investment

    The energy required to establish and maintain the electrochemical gradient.

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    Active Transport

    Movement of substances against the electrochemical gradient, requiring energy input.

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    Passive Transport

    Movement of substances down the electrochemical gradient without energy input.

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    Transport Proteins: Active vs Passive

    Active transport uses pumps and co-transport systems; passive uses channels and carriers.

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    Sodium/Potassium Pump

    A specific type of pump that uses ATP to transport sodium out and potassium in.

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    Bacteriorhodopsin

    A protein that uses light energy to transport protons across a membrane.

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    Conformational Change

    A structural alteration in a protein that allows it to perform its function.

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    Proton Pump

    A transport protein that moves protons (H+) across membranes using energy.

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    Co-Transporter

    A protein that couples the transport of one ion to another solute across a membrane.

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    Symport System

    A type of co-transport where both driver ion and solute move in the same direction.

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    Antiport System

    A co-transport mechanism where ions or solutes move in opposite directions.

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    Gated Ion Channels

    Proteins that open/close in response to stimuli like voltage or ligands.

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    Patch Clamp Technique

    A method used to measure single ion channel activity with a suction pipette.

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    Electrochemical Gradient Effects

    Combination of chemical and electrical gradients influencing ion movement across membranes.

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    Study Notes

    Membrane Transport

    • Membrane transport is NOT the movement of membranes themselves.
    • It involves the movement of molecules, especially ions, across biological membranes.
    • Also called 'trans'-membrane transport, ion transport, or nutrient transport.

    Importance of Membrane Transport

    • Necessary for protecting metabolic reactions inside cells from the environment.
    • Essential for communication and material exchange between the cell and its environment.
    • Transport proteins within the cell membrane control interactions between cells and the environment.

    Membrane Permeability

    • Highly permeable to small hydrophobic molecules and gases (e.g., oxygen).
    • Limited permeability to water.
    • Very low permeability to ions (e.g., potassium) and large solutes (e.g., glucose).

    Transport Proteins

    • Create hydrophilic passages.
    • Act as filters.
    • Enable energy coupling (where energy is linked to transport).
    • Allow for regulation.

    Facilitated Diffusion

    • Transport proteins form a hydrophilic pore.
    • Molecules diffuse through this pore.
    • Example: aquaporins (water channels).

    Driving Forces for Solute Transport

    • Chemical gradient: Difference in solute concentration.
    • Electrical gradient: Difference in charge.
    • Only relevant to charged molecules (ions).
      • Cations: Examples include proton (H+), potassium (K+), ammonium (NH₄⁺), histidine, and spermidine.
      • Anions: Examples include chloride (Cl⁻), nitrate (NO₃⁻), glutamate, malate, and pyruvate.

    Electrochemical Gradient

    • The net driving force for a molecule’s movement, resulting from the combination of chemical and electrical gradients.
    • Direction depends on the relative strengths of the chemical and electrical gradients, considering if the molecule is charged or uncharged.

    Energy Requirements of Transport

    • Electrochemical gradients determine energy needed for transport.
    • Energy investment is needed to move molecules against gradients (active transport).
    • Energy is gained when moving molecules down gradients (passive transport).

    Active and Passive Transport

    • Active transport: Moves substances against the electrochemical gradient; requires energy input.
    • Passive transport: Moves substances down the electrochemical gradient; requires no energy input, but still depends on previously established gradients.
    • Active transport is a prerequisite for passive transport, as the gradients are established by active transport.

    Transport Proteins for Active and Passive Transport

    • Transport proteins for active transport: Pumps, co-transport systems
    • Transport proteins for passive transport: Channels, carriers

    Pumps (Active Transport)

    • Energy coupling: ATP is used to power transport.
    • Examples of pumps: Sodium/potassium pumps, proton pumps, calcium pumps
      • e.g. Sodium/potassium pump transporter proteins bind 3 Na+ from inside the cell, get phosphorylated, releases 3 Na+, binds 2 K+ from outside the cell, dephosphorylated, releases 2K+ inside the cell.

    Co-transport Systems (Active Transport)

    • Couple the movement of one ion (driver) to the uphill movement of another solute (subscriber).
      • Symport: Driver ion and substrate move in the same direction.
      • Antiport: Driver ion and substrate move in opposite directions.

    Transport Coupling

    • Primary pumps use with co-transport systems in all life forms and function in organelles and cells.
    • Example: Na⁺/K⁺ ATPase and Na⁺-driven symport

    Passive Transport (cont.)

    • Movement of substances down the electrochemical gradient.
    • Relies on previously set electrochemical gradients.
    • Transport proteins for passive transport: Channels, carriers
      • Channels: create an aqueous pore for ion passage
      • Carriers: undergo conformational changes to expose binding sites to the membrane's different surfaces, allowing molecules to move through.

    Ion Channels

    • Exist as selective and gated pathways.
    • Selective permeability, e.g., K⁺ channels much more permeable to K⁺ than Na⁺.
    • Gated channels open/close in response to stimuli like voltage changes or ligand binding
      • An example of a gated channel would be voltage-gated channels which open and close in response to changes in membrane potential.

    Measuring Ion Channels

    • Patch-clamp measurement allow for measuring how single channel proteins gate.
    • Equipment includes suction pipette and amplifier.

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    L3 2025 Membrane Transport Tagged PDF

    Description

    Test your knowledge on membrane transport mechanisms, including the movement of molecules across biological membranes and the role of transport proteins. Explore the concepts of permeability, facilitated diffusion, and the importance of transport in cellular communication and metabolic reactions.

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