Final answer:
The true statement about enzymes is that most enzymes are proteins. Enzymes have high specificity for their substrates due to the shape of their active sites, and they function by lowering the activation energy for reactions without being consumed by those reactions.
Step-by-step explanation:
The correct statement about enzymes among the given options is: Most enzymes are proteins. Enzymes are crucial biological catalysts that significantly speed up the rate of chemical reactions without being consumed in the process. Although enzymes are predominantly proteins, not all proteins are enzymes since proteins have a wide variety of functions beyond catalysis.
Enzymes demonstrate high specificity for their substrates, which is largely attributed to the shape and chemical environment of the enzyme's active site. This specificity arises because of the unique three-dimensional structure formed by the amino acid residues within the enzyme, allowing only specific substrates to bind effectively.
Moreover, the active site of an enzyme binds to a substrate in a manner that lowers the activation energy required for the reaction, making the process more efficient. After the reaction, the enzyme releases the product and is ready to participate in additional reactions. Therefore, enzymes are not changed or consumed by the reactions they catalyze but may change shape during the process, which is a reversible alteration.