After you eat protein, it is partly hydrolyzed in the stomach using the enzyme pepsin. Other amino acids are put into the blood, so individual cells can remove them to use for their protein synthesis needs. Nucleic acids are the body chemicals that specify the types of proteins the body makes, and the proteins determine the rest of the body chemicals. Chromosomes, or their bacterial equivalents, are long chains of DNA coated with proteins. The individual nucleotides or small groups of them are then absorbed, and can be used to build up new DNA or RNA, or simply broken down to be used as an energy source.
Hormones are a functional class of chemicals.
Some are complex carbohydrates, others are proteins, which regulate the function of other chemical systems within the body. This is often accomplished by turning on and turning off genes, thus turning on or off the proteins made by those genes. The enzyme is a big protein which uses the energy from ATP to effect the bonding of the two molecules. Few body chemical reactions can proceed without enzymes.