Enzyme-Controlled Reactions
Applied Science: BTEC Level 3 National Extended Diploma, topic 3.3.4
Rate of Reactions
The rate of a reaction can easily be calculated. This means that changes in rates of reactions, due to a number of different factors, can be detected.
Calculating rate of reaction
- Rates of reaction can be calculated by measuring the increase in products or decrease in reactants over time.
- Calculating the gradient of a graph of this enzyme activity against time will give the rate of reaction in the appropriate units.
- Units depend on what quantity is being measured but include, cm3 s−1 (cubic centimetres each second) and g dm-3 s−1 (grams per decimetre each second).
Enzymes have optimal conditions
- Optimum conditions are where the enzyme works at its maximum rate. The same conditions are not optimum for every enzyme.
- The optimal pH for pepsin, a digestive enzyme found in the stomach, is around pH 1.5, whereas the optimal pH for pancreatic lipase is pH 8.
- Denaturation can occur if external conditions cause changes to the enzyme’s tertiary structure, altering the shape of the active site so that the substrate no longer fits.
Test yourself on Enzyme-Controlled Reactions
Which of the following statements about rate of reaction are true?
Which of these is NOT a way of measuring rate of reaction?