Biochemistry: Chemical Composition of Living Matter

Organic Compounds

• Organic compounds are carbon-containing, covalently bonded compounds in the body.
• Include four major classes of macromolecules: carbohydrates, lipids, proteins, and nucleic acids.
• Macromolecules are composed of smaller subunits known as monomers, linked by covalent bonds to form polymers.

Carbohydrates

• Found in grains, fruits, and vegetables; provide energy in the form of glucose.
• General formula: (CH₂O)n, with a carbon:hydrogen:oxygen ratio of 1:2:1.
• Three main subtypes: monosaccharides, disaccharides, and polysaccharides.

Monosaccharides

• Simple sugars with a single chain or ring structure.
• Examples include glucose (energy source), galactose (part of lactose), and fructose (part of sucrose).

Disaccharides

• Formed from two monosaccharides through dehydration synthesis, resulting in a covalent bond.
• Common disaccharides include maltose (grain sugar), lactose (milk sugar), and sucrose (table sugar).
• Hydrolysis is the process of breaking down disaccharides back into monosaccharides using water.

Polysaccharides

• Long branching chains of simple sugars; include starch (plant storage) and glycogen (animal storage).
• Starch has two components: amylose (unbranched, α 1-4 glycosidic bonds) and amylopectin (branched with α 1-4 and α 1-6 glycosidic bonds).
• Cellulose is a polysaccharide in plant cell walls, consisting of glucose monomers linked by β 1-4 glycosidic linkages, resulting in a fibrous structure.

Lipids

• Organic compounds comprised of carbon and hydrogen atoms.
• Triglycerides (neutral fats) consist of glycerol and fatty acid chains.
• Fats can be saturated (no double bonds, solid at room temperature) or unsaturated (at least one double bond, typically liquid at room temperature).

Saturated vs. Unsaturated Fatty Acids

• Saturated acids (e.g., stearic acid) pack tightly, can contribute to cardiovascular disease, and should be limited in the diet.
• Unsaturated fatty acids categorize into monounsaturated (one double bond) and polyunsaturated (multiple double bonds); generally liquid at room temperature.

Trans-Fats

• Formed from unsaturated fats with double bonds in either cis (same side) or trans (opposite side) configurations.
• Cis configuration leads to a kink in the chain, preventing tight packing; trans configuration allows for tighter packing.
• Trans-fats can negatively impact health, increasing LDL cholesterol levels in humans.