➢ Factors affecting reaction rates
○ Temperature
■ Although the rate of reaction increases with temperature, it only does so up to a point, because too much heat can denature an enzyme
■ $Q_10$
● Measure of sensitivity of a physiological process of enzymatic reaction rate
$Q_{10}=\left(\frac{R_2}{R_1}\right)^{\left(\frac{10}{T_2-T_1}\right)}$
- Temp must be celsius or kelvin
■ Same unit for $T_1 and T_2$ - Two reaction rates $(k_1 and k_2) $must have same unit
- Reaction rates with$ Q_10=1$ are temperature independent
- pH
■ Most enzyme’s ideal $\text pH$ is 7
➢ Enzyme Regulation
- Cell can control enzymatic reactions by regulating the conditions that change the shape of the enzyme
- Can be turned off/on by things that bind to them
■ Some bind at active site
■ Some bin at allosteric sites (non-active sites) - Competitive inhibition
■ If a substance has the exact complementary shape to the active site, it can compete with the substrate and block it from getting into the active site
■ If there is enough substrate available, it will out-compete the inhibitor and the reaction will occur
■ As substrate is used up, inhibitor out-competes the substrate and less reaction will occur - Allosteric inhibitors/Non Competitive inhibition
■ Binds to an allosteric site
■ Distorts shape of enzyme so it cannot function until the inhibitor is removed
■ Substrate can still bind if active site is intact, but the enzyme will not be able to catalyze the reaction
■ Activators can also be used to stabilize the enzyme’s active state
■ Inhibitors stabilize the inactive state
- Enzymes can also be controlled by negative feedback mechanisms
■ Product of reaction the enzyme is helping is also an allosteric inhibitor
■ Prevents a cell from wasting resources by synthesizing more of a product than is needed