What are enzymes? How are they named, and how do they speed up reactions? Use your textbook's example of the hydrolysis of sucrose.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define. Enzymes are biocatalysts, almost all globular proteins, each specific to one reaction and one substrate.
2 · Explain the naming. Usually the substrate's name with -ase: maltase hydrolyses maltose. Some are named after the reaction: oxidoreductases.
3 · Explain how they act. Like other catalysts they lower the activation energy, and they are needed only in small amounts.
4 · Give the textbook's example. Hydrolysis of sucrose: activation energy 6.22 kJ mol⁻¹ with acid, only 2.15 kJ mol⁻¹ with sucrase.
5 · Draw the energy profile. Plot energy against the progress of the reaction: a tall hump (acid) and a low hump (enzyme) between the same reactant and product levels. Label each activation energy.
6 · Link to real life. Amylase in saliva starts digesting the starch in chapati and rice.
7 · Close in one line. So a small amount of a specific enzyme makes a reaction fast at body temperature.
Scoring tip: Quote both activation energies with their units. They show that you know the textbook's example.
