Final answer:
Enzymes are primarily proteins that catalyze biochemical reactions by lowering activation energy, thus speeding up the reactions. They are specific to their substrates due to unique active sites formed by amino acid residues. The correct statements about enzymes are that they are composed of proteins and they lower activation energy.
Step-by-step explanation:
Enzymes play a critical role in biochemical reactions as they are specialized molecules that catalyze these reactions. The correct statements about enzymes are that they are mostly made up of proteins, and they lower the activation energy to speed up a chemical reaction. This lowering of activation energy facilitates the breaking and formation of chemical bonds more efficiently. Enzymes are highly specified as they bind to corresponding substrates at their active sites, which are unique chemical environments composed of specific amino acid residues.
Therefore, the statement that all enzymes are made up of proteins (I) is true, and they lower activation energy to speed up a chemical reaction (II) is also true. The statement that all enzymes are made up of nucleic acids (III) is incorrect, as enzymes can also be made from RNA, but primarily, they are protein in nature. The correct answer to the provided question is that enzymes are made of proteins and they lower activation energy, making the correct option (C) I, III.