Figure 1.2
Operation of a feedback system.

Figure 1.5 The anatomical position.

Figure 1.6 Directional terms.

Figure 1.7
Planes through the human body.

Figure 1.9 Body cavities.

Figure 2.1
Two representations of the structure of an atom.

Figure 2.2
Atomic structures of several stable atoms.

Figure 2.5
Covalent bond formation.

Figure 2.6 Hydrogen bonding among water molecules.

Figure 2.12
The pH scale.

Table 2.5
Major Functional Groups of Organic Molecules

NAME AND STRUCTURAL FORMULA*
OCCURRENCE AND SIGNIFICANCE

Alcohols contain an ─OH group, which is polar and hydrophilic due to its electronegative O atom. Molecules with many ─OH groups dissolve easily in water.

Thiols have an ─SH group, which is polar and hydrophilic due to its electronegative S atom. Certain amino acids (for example, cysteine) contain ─SH groups, which help stabilize the shape of proteins.

Ketones contain a carbonyl group within the carbon skeleton. The carbonyl group is polar and hydrophilic due to its electronegative O atom.

Aldehydes have a carbonyl group at the end of the carbon skeleton.

Carboxylic acids contain a carboxyl group at the end of the carbon skeleton. All amino acids have a ─COOH group at one end. The negatively charged form predominates at the pH of body cells and is hydrophilic.

Esters predominate in dietary fats and oils and also occur in our body as triglycerides. Aspirin is an ester of salicylic