To determine which statement is not true about enzymes, let’s examine each option:
- 1. They lower the activation energy of chemical reactions: This statement is true. Enzymes act as catalysts and lower the activation energy required for chemical reactions, making it easier for reactions to occur.
- 2. They are consumed by reactions they catalyse: This statement is not true. Enzymes are not consumed in the reactions they catalyse. Instead, they can be used repeatedly to facilitate many reactions without being depleted.
- 3. Each one is specific to a particular substrate to which it binds: This statement is true. Enzymes are highly specific and typically bind to a specific substrate, which is the reactant in the reaction they catalyse.
- 4. They are made of amino acids: This statement is true. Enzymes are indeed proteins, and proteins are made up of long chains of amino acids.
Therefore, the statement that is not true about enzymes is option 2: they are consumed by reactions they catalyse.