Membrane transport

Card Set Information

Membrane transport
2014-03-11 15:31:32
chapter 11
chapter 11
Show Answers:

  1. What is active transport:
    Active transport: Energy-requiring transport of a solute across a membrane in the direction of increasing concentration, against concentration gradient.
  2. What are passive mechanisms:
    Passive mechanisms: diffusion of a polar substance across a biological membrane through a protein transporter.
  3. What is facilitative transport?
    Facilitative transport:  when proteins that span a membrane add transport specific nutrients, metabolites, ions, or proteins across the membrane.
  4. What is passive transport?
    Passive transport: is facilitated by membrane proteins. 2 compartments, unequal solute concentrations, separation of compartments by permeable barrier. Diffusion of a polar substance across a biological membrane through a protein transporter; also called facilitated diffusion.
  5. What is the difference between simple and facilitated diffusion?
    The difference between them are: diffusion requires no help, facilitated diffusion needs a transport protein.
  6. What are the components of electrochemical gradients?
    Components of electrochemical gradients: electrical potential and a difference in the chemical concentration across a membrane.
  7. Definition of elctrochemical gradient:
    Definition of electrochemical gradient: Selectively permeable membrane plus unequal distribution of charged solute. This results in unequal solute concentration and charge concentration between the two sides of the membrane. An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane.
  8. What is membrane potential?
    Membrane potential: an electrical gradient caused by unequal charge distribution.
  9. How do water, glucose, and other solutes get transported across membranes without the need for energy expenditures?
    To get through a membrane, any solute must: (1) strip away solation layer (2) move past hydriphobic molecules (3) rehydrate. Physical barrier must be overcome with energy, so much energy that membranes are virtually impenetrable to polar solutes.
  10. What are the fundamental mechanisms for transporting solutes across membranes?
    Two fundamental mechanisms for transporting solutes across membranes: Passive transport (facilitated diffusion) and active transport (expend energy to go against gradient).
  11. Define uniport, symport, and antiport:
    • Uniport : only one solute is
    • transported.

    • Symport: 2 different solutes move in the
    • same direction. Facilitated diffusion.

    • Antiport: an exchanger. Facilitated
    • diffusion.
  12. What is primary active transport?
    Primary active transport: solute accumulation is coupled directly to an exergonic chemical reaction, such as conversion of ATP to ADP + Pi. Because active transport is thermodynamically unfavorable (endergonic) and takes place only when coupled (directly or indirectly) to an exergonic process such as the absorption of sunlight, an oxidation reaction, the breakdown of ATP, or the concomitant flow of some other chemical species down its electrochemical gradient.
  13. What is secondary transport?
    Secondary active transport: occurs when endergonic (uphill) transport of one solute is coupled to the exergonic (downhill) flow of a different solute that was originally pumped uphill by primary active transport.
  14. ligand-gated channel:
    Ligand-gated channels: binding of an extracellular or intracellular small molecule forces an allosteric transition in the protein, which opens or closes the channel.
  15. voltage-gate ion channel:
    Voltage-gates ion channels: a change in transmembrane electrical potential, Vm, causes a charged protein domain to move relative to the membrane, opening or closing the channel.