1. Carbohydrates: These are composed of carbon, hydrogen, and oxygen. They serve as a primary energy source for cells, provide structural support, and play a role in cell signaling and recognition. Examples include sugars (glucose, fructose), starches, and cellulose.

2. Lipids (Fats & Oils): These are diverse molecules characterized by being largely nonpolar and hydrophobic. Lipids store energy, form cell membranes, act as hormones, and provide insulation. Examples include triglycerides, phospholipids, cholesterol, and steroids.

3. Proteins: These are complex polymers made up of amino acid chains. They have diverse functions, including enzymes (catalyzing reactions), structural components (like collagen in connective tissue), transport molecules (like hemoglobin), and hormones (like insulin).

4. Nucleic Acids: These are complex molecules that store and transmit genetic information. They are made of nucleotides, each consisting of a sugar, a phosphate group, and a nitrogenous base. DNA (deoxyribonucleic acid) holds the genetic code, while RNA (ribonucleic acid) is involved in protein synthesis.