Molecules of Life Overview

Cells are primarily composed of water and carbon-based organic compounds.
Organic compounds contain carbon; simplest form is hydrocarbons (only carbon and hydrogen).
Four major classes of organic molecules: carbohydrates, lipids, proteins, and nucleic acids.

Known as macromolecules due to large size.
Also referred to as polymers, constructed from smaller subunits called monomers.
Monomers serve as building blocks for larger polymers.

Main source of energy for cellular functions.
Building blocks are simple sugars known as monosaccharides.
Three classes include:
- Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose).
- Disaccharides: Formed from two monosaccharides via dehydration reactions (e.g., sucrose, maltose, lactose).
- Polysaccharides: Long chain polymers made of monosaccharides (e.g., starch, glycogen, cellulose).

Hydrophobic compounds that do not mix well with water.
Key types include fats, phospholipids, and steroids.
Fats serve mainly as energy storage, composed of glycerol and fatty acids, typically in triglyceride form.
Phospholipids form cell membranes, consisting of two fatty acids and a phosphate group, creating hydrophobic tails and hydrophilic heads.
Steroids consist of fused ring structures; cholesterol is an important steroid that supports cell membrane structure and synthesizes sex hormones.

Polymers made from amino acid monomers.
Composed of 20 different amino acids linked by peptide bonds, creating long protein chains.
Amino acids consist of an amino group, a carboxyl group, and a variable side chain (R group).
Functions encompass:
- Structural components (e.g., actin, myosin in muscles).
- Defensive roles (e.g., antibodies).
- Transport functions (e.g., hemoglobin).