Answer :
Answer: A. Lowers activation energy
Explanation: The main purpose of an enzyme is to lower the activation energy of a chemical reaction, thus facilitating them and making reactions more energy efficient. This is done through enzymes binding with substrates (specific reactants that enzymes bind to and work on) and holding them in a position where bond-forming and bond-breaking processes can occur more readily.
Choice B is incorrect because enzymes are not consumed in a reaction. Enzymes merely bind to substrates and catalyze the reaction. Once the reaction has been completed, substrates are unbound from the enzymes, thus allowing enzymes to be re-used in multiple reactions. Enzymes themselves are not reactants, they are simply catalysts for a reaction. Thus, they're not consumed in a reaction.
Choice C is incorrect because enzymes are altered by changes in pH. In fact, most enzymes have an optimal pH level that they work best at. This is because the bonds that make up an enzyme are especially sensitive available H+ or OH- molecules that could alter bond structure. As a result, changes in pH can denature enzyme structure, resulting in enzymes unfolding or becoming malformed. This can drastically change enzyme efficiency.
Choice D is incorrect because enzymes are proteins, not RNA molecules. Enzymes are proteins that are made up of multiple amino acid sequences bonded and folded together. Enzymes are not made up of nucleotides or RNA.
