A%20Balancing%20Act:%20Direct%20and%20Indirect%20Active%20Transport

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A Balancing Act Direct and Indirect Active
Transport
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The Basics

• The cell is the coolest thing ever.
• A cell is picky about its living conditions.
• Intracellular K ion concentration is maintained
  at 100-150 mM (351 inside to outside ratio).
• Intracellular Na ion concentration is
  maintained at 10-15 mM (0.081 inside to outside
  ratio).

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Direct Active TransportSodium Potassium Pump

• Pump is a transmembrane protein composed of two a
  and two ß subunits.
• Responsible for maintaining the sodium/potassium
  ion gradient.
• Pump uses ATP for energy, therefore it is also
  known as Na/K ATPase.
• The sodium/potassium gradient is a key factor in
  nerve impulse transmission and protecting the
  cell from swelling.

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Indirect Active TransportSodium/glucose
Symporter

• Facilitates movement of glucose into blood via
  sodium/glucose symporter protein.
• Driven by uptake of sodium ions.
• Occurs in epithelial cells that line the
  intestine.
• Occurs when glucose concentration levels are
  lower than in the epithelial cells.

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Steps of Na/Glucose Symporter Cycle

• Pump open to outside of cell.
• Sodium ion bonds, leads to confirmation change.
• Glucose binds, another confirmation change.
• Pump opens to inside.
• Sodium falls off.
• Glucose falls off.
• Pump returns to original state.

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Conclusion

• Cells use direct and indirect active transport to
  maintain its picky lifestyle.
• Sodium potassium pump is an example of direct
  active transport.
• Sodium/glucose symporter is an example of
  indirect active transport.

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• QUESTIONS?