Final answer:
An enzyme is a specialized protein that catalyzes biochemical reactions by lowering activation energy, speeding up the process without altering the reaction's overall energetics.
Step-by-step explanation:
A specialized protein that catalyzes biochemical reactions is known as an enzyme. Enzymes are typically proteins that consist of chains of amino acids, facilitating the speeding up of chemical reactions within living cells by lowering the necessary activation energy. They achieve this by binding to reactant molecules, thus enabling bond-breaking and bond-forming processes more efficiently. However, it is crucial to note that enzymes do not alter the reaction's Gibbs free energy (ΔG), meaning they do not affect whether a reaction is exergonic (spontaneous) or endergonic; they solely reduce the activation energy required for the reaction to proceed to the transition state. Examples of enzymes include salivary amylase, which acts on the substrate amylose in starch.