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A-Level Biology OCR A

Cell Transport Bonds Describe Auxins Iaa Lead Growth

Auxin, produced at the tip of shoots and roots, moves to the cell wall, increasing H+ concentration, which breaks hydrogen bonds and activates expansins to break cellulose bonds, making the wall less rigid and allowing the cell to expand.

L'auxine, produite à la pointe des pousses et des racines, se déplace vers la cellule de la paroi, augmentant la concentration de H+, ce qui décompose les liaisons d'hydrogène et active les expansines pour rompre les liaisons de cellulose, rendant la paroi moins rigide et permettant à la cellule de se dilater.

Front Describe how auxins such as IAA, lead to growth.
Back Auxin action:
  • Made it cells at tip of roots and shoots & in meristems
  • Move up/down through transport tissue and cell to cell
  • Bind to receptors on CSM, triggering second messenger cascade
  • This causes active transport of H+ into cell wall
  • Increased H+ conc disrupts hydrogen bonds and low pH (5) is optimum for expansins which break bonds within cellulose
  • Walls become less rigid
  • Plant expands as cell takes in water

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