This lecture note summarises the kinetics and thermodynamics of enzyme reaction. It elaborates on the 1st and 2nd order rate, rate determining step, collision theory, activation energy, and Arrhenius theory.
Energy transformations
- Conversion of chemical E in nutrients to another form of chemical bond E in ATP
- Conversion of bond E in ATP to cellular work
- Osmotic work (ion pumps)
- Mechanical work (muscle contraction)
- Metabolic work (driving E-requiring biosynthetic reactions)
Chemical Kinetics
The rate of reaction: proportional to the frequency with which the reacting molecules simultaneously collide
The order of reaction: the sum of exponents
- Order = how many molecules have to bump into each other at one time for a reaction to occur
- Zero order: rarely occurs
- 1st order: when on molecule change to another A → B
- 2nd order: when 2 molecules react A + B → P + Q / 2A → P
- 3rd order: rarely occurs A+B+C → P+Q+R
1st Order Rate
→B
V = velocity of the reaction (M/min)
K = rate constant of the reaction
- Mostly, the reactions are reversible and equilibrium does not lie far to one side
- Natural log of the concentration ([A]) id directly proportional to the time
K for 1st order reaction has unit: s-1
Instantaneous rate: the rate of reaction at any specified time point that is the definition
of the derivative
- Half life: time for half of the reactant which is initially present to decompose or change
→ used to determine the amount of material left after a length of time
Radioactive isotope emits an energetic β particle and has a half-life of 14 days
→ half life of 1st order reaction is not dependent on the intial concentration
2nd Order Rate
→P →P+Q
- % change in A versus time
Enzymes Page 1
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