Hemoglobin serves as a chemical messenger
In DNA<span>, the code letters are A, T, G, and C, which stand </span>for<span> the chemicals </span>adenine<span>, thymine, guanine, and cytosine, respectively. In base pairing, </span>adenine always pairs<span> with thymine, and guanine </span>always pairs<span> with cytosine.</span>
The substrate is the part that sticks into the active site of an enzyme.
