Final answer:
The true statement about enzymes and substrates is that enzymes are specific about the substrates they can act upon, binding them at the active site to catalyze chemical reactions.
Step-by-step explanation:
The correct answer to which statement is true about enzymes and substrates is c. enzymes are specific about the substrates they can act upon. Enzymes increase the rate of a chemical reaction by lowering the activation energy required. They achieve this by binding to their substrates at a part of the enzyme called the active site. This site is highly specific, allowing only certain substrates to bind, akin to a key fitting into a specific lock. The binding typically involves non-covalent interactions, such as hydrogen bonds, ionic bonds, and hydrophobic interactions. However, some enzymes can form transient covalent bonds with the substrate during the reaction, as seen in covalent catalysis.
Once the substrate is bound, the enzyme catalyzes the reaction, converting the substrate into product(s). After the reaction, the products are released, leaving the enzyme ready to catalyze another reaction. This specificity ensures that enzymes operate efficiently within the complex environment of a living organism, catalyzing the correct reaction out of many possible ones.