L20: Catalytic Power Flashcards Preview

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Flashcards in L20: Catalytic Power Deck (7)
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1
Q

High energy transition state

A

Bonds are partially broken (enthalpy change positive), reactants become more ordered (entropy change negative)

Free energy of activation = enthalpy change - temp x entropy change -> free energy of activation always positive

2
Q

Catalyst

A

Lower free energy of transition state

Stabilise transition state

Reduce free energy of activation -> increase rate constant for reaction

3
Q

Transition states in enzyme catalysed reactions

A
  1. Binding of substrate to enzyme active site
  2. For the reaction itself
  3. For dissociation of product from enzyme active site
4
Q

Intermediates

A

Enzyme-catalysed reactions proceeds via intermediates that don’t occur in uncatalysed reaction

Advantage of having intermediate: reaction split into 2 separate steps -> each have own transition state. Have lower free energies of activation -> enhancing rate of reaction

5
Q

Arrhenius plots

A

Describe temp dependency of rate constant for reaction

In enzyme catalysed reactions: rate of reaction is measured at high (saturating) [subs] at different temps -> rate of reaction is function of rate constant of rate limiting step in reaction, kcat

Gives activation energy, Ea

R: gas constant

6
Q

Catalytic power

A

Ratio of rate constant of catalysed reaction to that of uncatalysed reaction

7
Q

Calculated activation parameters

A

Give info about enthalpy and entropy changes required to get transition stage of slowest step of reaction i.e. one with highest energy barrier that governs rate if overall reaction