Activation energy is best defined as the energy

Correct answer: C. needed to bring the reactants to the transition state so the reaction can proceed

  • A. released when the products are formed
  • B. stored in the bonds of the substrate
  • C. needed to bring the reactants to the transition state so the reaction can proceed
  • D. used by the enzyme to bind the substrate

Explanation

Even an energetically favourable reaction needs an initial input to break existing bonds and reach the unstable transition state, and that barrier is what keeps sugars from spontaneously oxidising in the air. An enzyme lowers the barrier by stabilising the transition state, so far more molecules can cross it at body temperature. The energy difference between reactants and products is a separate quantity that the enzyme does not change.

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About Mode of Enzyme Action

Enzyme action depends on the active site forming a temporary enzyme substrate complex, then converting substrate into products with lower activation energy. The lock and key and induced fit models explain specificity and binding, while cofactors and changes in enzyme shape can affect catalysis.

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