Final answer:
Proteins that catalyze chemical reactions are called enzymes. They lower the activation energy for reactions, allowing them to proceed more quickly and efficiently. The correct answer is a. Enzymes.
Step-by-step explanation:
Proteins that control or catalyze chemical reactions are called enzymes. These biological catalysts accelerate reactions by lowering the activation energy, which means they make it easier for chemical reactions to take place without being permanently altered themselves. Enzymes are usually made up of one or more polypeptide chains and possess an active site. This site provides a unique chemical environment suited for specific reactants known as substrates, facilitating their conversion into other compounds through the reaction process. The specificity of enzymes is attributed to their shape and the unique combination of amino acid side chains within the active site, allowing them to work on particular substrates with an induced fit model, adapting their shape for optimal binding.
The correct answer to the student's question is a. Enzymes.