Figure 03.UN00b Title: Hydrolysis Caption: Hydrolysis of biological molecules.

Figure 03.UN00e Title: Structures of ribose and deoxyribose Caption: Structures of ribose and deoxyribose.

Figure 03.1 Title: Synthesis and breakdown of a disaccharide Caption: The disaccharide sucrose is synthesized by a dehydration synthesis reaction in which a hydrogen (–H) is removed from glucose and a hydroxyl group (–OH) is removed from fructose. A water molecule is formed in the process, leaving the two monosaccharide rings joined by single bonds to the remaining oxygen atom. Hydrolysis of sucrose is just the reverse of its synthesis, as water is split and added to the monosaccharides.

Figure 03.UN07 Title: Amino acid functional groups Caption: Amino acid functional groups.

Figure 03.9 Title: Amino acid diversity Caption: The diversity of amino acid structures is a consequence of differences in the variable R group (colored blue). Some amino acids are classified according to the variable R group as hydrophilic, others as hydrophobic. Cysteine stands in a class by itself. Two cysteines in distant parts of a protein molecule can form a covalent bond between their sulfur atoms, creating a disulfide bridge that brings the cysteines very close together and bends the protein chain.

Figure 03.UN00a Title: Dehydration synthesis Caption: Dehydration synthesis is used to form biological molecules.

Figure 03.10 Title: Protein synthesis Caption: In protein synthesis, a dehydration synthesis joins the carbon of the carboxyl acid group of one amino acid to the nitrogen of the amino group of a second amino acid. The resulting covalent bond is called a peptide bond.

Figure 03.UNE1 Title: Hair structure Caption: Hair structure.

Figure 03.11 Title: The four levels of protein structure Caption: Levels of protein structure are represented here by hemoglobin, the oxygen-carrying protein in red blood cells. All levels of protein structure are determined by the amino acid sequence of the protein, interactions among the R groups of the amino acids (primarily hydrogen bonds and disulfide bridges between cysteines), and interactions between the R groups and their surroundings (generally water or lipids).

Figure 03.12 Title: The pleated sheet is an example of protein secondary structure Caption: In a pleated sheet, several peptide chains lie side by side (here shown horizontally). Hydrogen bonds between peptides (vertical dotted lines) hold the peptide chains together. The R groups (green) project alternately above and below the sheet. Despite its accordion-pleated appearance, each peptide chain is in a fully extended state and cannot easily be stretched farther. For this reason, pleated sheet proteins such as silk are strong, but not elastic.

Figure 03.UN12a Title: Deoxyribose nucleotide Caption: Deoxyribose nucleotide.

Figure 03.UN12b Title: Nucleotide chain Caption: Nucleotide chain.

Figure 03.13 Title: A sampling of the diversity of nucleotides Caption: Individual nucleotides, constructed of a sugar, a phosphate group, and a nitrogen-containing base, are often modified by the addition of different functional groups and serve a variety of cellular functions.

Figure 03.13a Title: Cyclic AMP Caption:

Figure 03.13b Title: ATP Caption:

Figure 03.13c Title: Coenzyme Caption: