2.2. The molecular parts list[[Student version, December 8, 2002]] 43
Figure 2.14:(Molecular structure diagrams.) Adenosine triphosphate is hydrolyzed as part of many biochemical
processes. An ATP and a water molecule are both split, yielding ADP, inorganic phosphate (Pi), and a proton (H+).
Asimilar reaction yielding about the same amount of free energy splits ATP into adenosine monophosphate (AMP),
acompound with one phosphate group, and pyrophosphate, or PPi.Chapter 8 will discuss chemical energy storage;
Chapter 10 will discuss molecular motors fueled by ATP. [Copyrighted figure; permission pending.]
Figure 2.15:(Molecular structure diagrams.) (a)Formation of a polypeptide from amino acids by the condensation
reaction, essentially the reverse of the hydrolysis reaction shown in Figure 2.14. The four atoms in each gray
boxconstitute the “peptide bond.” (b)Ashort segment of a polypeptide chain, showing three residues (amino
acid monomers) joined by two peptide bonds. The residues shown are respectively histidine, cysteine, and valine.
Chapters 7–8 will discuss the interactions between the residues that determine the protein’s structure; Chapter 9 will
briefly discuss the resulting complex arrangement of protein substates. [Copyrighted figure; permission pending.]