Craven Flashcards
What is the equation for a unimolecular irreversible reaction?
k
A —–> B
In a unimolecular irreversible system, why do molecules last in state A for diff amounts of time?
- undergo diff collisions
- stochastic process
In a unimolecular irreversible system, what is the average amount of time spent in A?
- DIAG*
- 1 / k
In a unimolecular irreversible system what is the rate of change of no. molecules in state A?
- -kNA
- where NA = no. molecules in state A
In a unimolecular irreversible system what is the rate of change of [A]?
- -k[A]
What order is the rate constant in a unimolecular irreversible system?
- 1st order
What is the numerical solution of rate equation, for unimolecular irreversible systems?
- set of values of [A] at set of times for particular values (discrete)
Why is the numerical solution always slightly approx compared to analytical solution, and how can it be made more accurate?
- assumes ROC of [A] constant during whole timestep
- use smaller timestep
What is the analytical solution of the rate equation for unimolecular irreversible systems, and how is it calc?
- works out equation for [A] as function of time
- [A] = [A]0e^-kt
What are the advantages of the analytical solution of the rate equation, for unimolecular irreversible systems?
- works for any [A]0, k and t
- exact
What are the disadvantages of the analytical solution of the rate equation, for unimolecular irreversible systems?
- need to know lots of maths
- only poss to find in simple cases
What are the advantages of the numerical solution of the rate equation, for unimolecular irreversible systems?
- maths easy
- totally general, can apply to v complex biological models
What is the disadvantage of the numerical solution, for unimolecular irreversible systems?
- slightly approx
What is the [A] at t=0, and why?
- [A] = [A]0e^kx0
- ∴ [A] = [A]0
What is the [A] if let t become v big?
- kt v big
- e^kt v big
- so e^-kt = 0
- [A] = 0 (all A used up)
How is half life calc?
- 0.693/k
How can [B] be calc in terms of [A]?
- [B] = [A]0 - [A]0e^-kt
- [B] = [A]0 (1-e^-kt)
What is the equation for a biomolecular irreversible reaction?
k
- A + B —–> C
What order is the rate constant in a biomolecular irreversible system?
- 2nd order
In a biomolecular irreversible system, what is the average time spent in A?
- 1 / k[B]
In a biomolecular irreversible system, how does [A] relate to [B]?
- from perspective of A, rate of making collisions w/ B is dep on [B]
- in ideal solution rate directly proportional to to [B]
In a biomolecular irreversible system, how is the rate of change of [C] calc?
- k[A][B]
What is the diffusion controlled limit in biomolecular irreversible systems?
- typically most collisions unsuccessful, but collision can occur straight away
- if [B] = 1mM, time for collision ≈1μs
- av time = 1 / k[B]
- so 1μs = 1 / k x 1m
10^-6s = 1 / k x 10^3M
k = 10^9M^-1s^-1 - approx largest value of 2nd order rate constant, so reaction can’t go faster than this
- but k generally a lot smaller
Why are calcs of reaction time courses much more complex for biomolecular irreversible system than unimolecular?
- likelihood of A reacting (in next moment of time) changes as B used up
- or opp true