Notes on quantitative biology

Separation of time scales

Reaction rate is proportional to the product of reactant concentrations, each raised to the power of how many molecules participate in that step.
Assumptions:
- Well-mixed, homogeneous, dilute solution.
- Constant temperature and volume.
- Reaction steps are truly elementary (no hidden multi-step mechanism).
- No transport limitation (reaction, not diffusion, is rate-limiting).
Expect deviations if you see:
- Saturation (e.g., enzyme binding sites saturate).
- Cooperative/allosteric effects (sigmoidal responses).
- Crowding/phase separation, surface reactions, or diffusion limitation.
- Complex mechanisms lumped into a single “overall” step.