I. Inorganic Molecules (p. 77)

A. Water (p. 77)

1. The important properties of water are attributable to its polar covalent bonds and its V shape. (fig. 3.1; TR 63; table 3.1)

2. These properties make water a good solvent, transport medium, coolant, and lubricant, as well as a ready participant in chemical reactions.

3. Solvency

a. Solvency is the ability to dissolve matter; water is called the universal solvent.

b. Molecules that dissolve readily in water are hydrophilic; those that do not are hydrophobic.

c. When NaCl is dissolved in water, water molecules form a hydration sphere around each sodium and chloride ion.

4. Adhesion and Cohesion

a. Adhesion is the tendency of one substance to cling to another; cohesion is the tendency of molecules of the same substance to cling together.

b. Water is highly cohesive, as evidenced by its high surface tension.

5. Thermal Stability

a. Water has a high heat capacity, meaning that it takes a large amount of heat to change the temperature of water.

6. Chemical Reactivity

a. Water is a reactant or product in numerous chemical reactions within the body.

B. Minerals (p. 79)

1. Minerals are inorganic elements passed to us through the food chain; they make up about 4% of the human body by weight.

2. Most of the mineral content of the body is calcium and phosphorus, which contribute to the structure of body parts (i.e., bone).

3. Minerals also take part in many metabolic reactions as cofactors or electrolytes.

C. Gases (p. 79)

1. Carbon dioxide and oxygen are the two most important gases in the body.

2. Certain gases are also used as chemical messengers, such as nitric oxide.

II. Carbon and Organic Molecules (p. 79)

A. Carbon (p. 80)

1. Carbon is used extensively by organisms. It reacts readily to form four covalent bonds, giving it the ability to form long chains.

B. Functional Groups (p. 80)

1. A functional group is a small cluster of atoms that determines many of the properties of the organic molecule. (fig. 3.2; TR 64)

C. Monomers and Polymers (p. 80)

1. Large organic molecules are called macromolecules. These are mostly polymers—repeating series of subunits (building blocks) called monomers.

2. The joining of monomers to form a polymer is called polymerization; this occurs by dehydration synthesis. (fig. 3.3a; TR 65)

3. Breaking polymers apart requires the addition of water through hydrolysis. (fig. 3.3b)

III. Carbohydrates (p. 81)

A. Monosaccharides (p. 81)

1. The simple sugars are the monosaccharides that serve as the monomers for polysaccharides.

2. Glucose, fructose, and galactose are the three monosaccharides of primary importance; all have the molecular formula C₆H₁₂O₆. (fig. 3.4; TR 66)

B. Disaccharides (p. 82)

1. Two monosaccharides joined together become a disaccharide.

2. Table sugar, sucrose, is made up of glucose + fructose; the other two major disaccharides are lactose and maltose. (fig. 3.5; TR 67)

3. The C–O–C bonds that hold the disaccharides together are called glycosidic bonds. (fig. 3.6; TR 68)

C. Polysaccharides (p. 82)

1. Polymers of glucose are called polysaccharides. (fig. 3.7; TR 69)

2. Starch is a polysaccharide that serves to store energy for plants.

3. The polysaccharide cellulose gives plant cell walls strength and gives roughage to the human diet.

4. Glycogen is the polysaccharide form animals and humans use to store energy.

D. Carbohydrate Functions (p. 83; table 3.2)

1. Carbohydrates serve primarily as a source of energy.

2. Carbohydrates are also often conjugated with proteins and lipids, forming glycoproteins and glycolipids (components of the glycocalyx of cells). Glycoproteins are also a major component of mucus.

3. Proteoglycans (mucopolysaccharides) hold cells and tissues together, lubricate joints and are a component of cartilage, among other functions.

IV. Lipids (p. 85)

A. Fatty Acids (p. 85; table 3.3)

1. Fatty acids are one type of lipid, hydrophobic organic molecules with a high ratio of H to O.

2. Fatty acids are chains of 4 to 24 carbon atoms with a carboxyl group at one end and a methyl group at the other.

3. Fatty acids are saturated (with a hydrogen at every position along the carbon chain) or unsaturated (missing a carbon, and with a double bond). (fig. 3.8; TR 70)

4. Polyunsaturated fatty acids have multiple C=C bonds.

B. Triglycerides (p. 86)

1. A triglyceride is a neutral fat made up of three fatty acids bound to a molecule of glycerol.

2. Dietary triglycerides take the form of oils (from plants) and animal fat.

3. In the body, triglycerides store energy in adipose tissue and provide insulation and cushioning.

C. Phospholipids (p. 87)

1. Phospholipids contain two fatty acids and a phosphate group. (fig. 3.9; TR 71)

2. They have a polar hydrophilic region (phosphate group end) and hydrophilic fatty acid tails (hydrophobic area).

3. They serve as the structural foundation of cell membranes.

D. Eicosanoids (p. 87)

1. Prostaglandins, the most functionally diverse eicosanoids, are fatty acids modified into a ring structure. (fig. 3.10; TR 72)

2. Prostaglandins are produced in almost all types of tissue and serve as intercellular messengers.

E. Steroids (p. 87)

1. Steroids are lipids with complex ring structures.

2. Examples include cholesterol and steroids formed from it. (fig. 3.11; TR 73)

V. Proteins (p. 87)

A. Amino Acids (p. 88)

1. A protein is a polymer of amino acids.

2. An amino acid has a carboxyl end and an amino end as well as a variable R group. (fig. 3.12; TR 74)

3. Twenty kinds of amino acids are used in protein structure. (table 3.4)

B. Peptides (p. 89)

1. A peptide is two or more amino acids joined by peptide bonds.

2. The peptide bond is formed between the amino group of one amino acid and the carboxyl group of the next.

3. Peptides vary according to size: dipeptides, tripeptides, oligopeptides, and polypeptides. (fig. 3.13; TR 75)

C. Levels of Protein Structure (p. 90; figs. 3.14–3.16; TR 76-78)

1. Primary structure refers to the order of the amino acids in the peptide.

2. Secondary structure is a coiled or folded shape held together by hydrogen bonds.

3. Tertiary structure is formed by further bending and folding of the proteins.

4. Quaternary structure occurs between two or more polypeptide chains.

D. Protein Conformation and Denaturation (p. 92)

1. Protein conformation refers to its overall shape. It cannot function properly if the shape is altered.

2. Denaturation due to heat or changes in pH causes a protein to unwind and destroys it.

E. Conjugated Proteins (p. 92)

1. Conjugated proteins have a non-amino acid prosthetic group bound to them, such as hemoglobin.

F. Protein Functions (p. 92)

1. Proteins serve as structural components and as enzymes in catalysis as well as for communication, membrane transport, cell recognition and protection, and movement and adhesion.

VI. Enzymes and Metabolism (p. 93)

A. Enzyme Structure and Action (p. 94; table 3.5)

1. Enzymes are proteins that function as catalysts.

2. Enzymes serve to lower the energy of activation in a chemical reaction, causing it to proceed. (fig. 3.17; TR 79)

3. Enzymes are not altered by acting as catalysts.

4. Enzymes are named for the substrate upon which they act, adding the suffix -ase to the substrate name.

5. Portions of enzyme molecules serve as active sites where substrate molecules attach. (fig. 3.18; TR 80)

6. Enzymes are specific for their substrates (enzyme-substrate specificity), adjusting shape slightly to accommodate the substrate (induced-fit) and thus forming an enzyme-substrate complex.

7. Enzymes are temperature and pH sensitive, since slight changes can disrupt the hydrogen bonds holding the molecule in its proper conformation.

B. Cofactors (p. 95)

1. Many enzymes require nonprotein cofactors to function properly.

2. Many enzymes work in conjunction with organic coenzymes. (fig. 3.19; TR 81)

C. Metabolic Pathways (p. 96)

1. Metabolic pathways require a sequence of enzymes to catalyze each reaction in turn.

2. By activating or deactivating enzymes, cells can turn on metabolic pathways when their end products are needed and shut them down when those products are not needed.

VII. Nucleotides and Nucleic Acids (p. 96)

A. Adenosine Triphosphate (p. 96)

1. Adenosine triphosphate (ATP) is the universal energy-carrying molecule.

2. ATP consists of a double carbon-nitrogen ring (adenine), a five carbon sugar (ribose), and a chain of three phosphate groups. (fig. 3.20; TR 82)

3. Most energy transfers involve removing the terminal phosphate group, employing ATPases.

4. ATP is short-lived but is regenerated via phosphorylation.

5. The oxidation of glucose is the primary source of energy to synthesize ATP. (fig. 3.21; TR 83)

6. The first stage of oxidation is glycolysis, in which glucose is split into two three-carbon molecules of pyruvic acid. (fig. 3.22; TR 84)

7. If no oxygen is available, pyruvate enters anaerobic fermentation, a more inefficient pathway.

8. If oxygen is available, aerobic respiration occurs within the mitochondria.

B. Other Nucleotides (p. 98)

1. Guanosine triphosphate (GTP) is another energy-transferring molecule.

2. Cyclic adenosine monophosphate (cAMP) is a molecule that acts as a "second messenger" to activate metabolism within a cell.

C. Nucleic Acids (p. 98)

1. Nucleic acids are polymers of nucleotides.

2. Deoxyribonucleic acid (DNA) is the largest nucleic acid and the one that constitutes our genes and is responsible for transferring hereditary information.

3. Ribonucleic acid (RNA) exists in three forms and functions to synthesize the body’s proteins by assembling amino acids in the order described by DNA.