1. Carbohydrates: These are composed of carbon, hydrogen, and oxygen, often in a 1:2:1 ratio. They serve as a primary energy source for living organisms and are also involved in structural support. Examples include sugars, starches, and cellulose.

2. Lipids (Fats & Oils): These are composed of carbon, hydrogen, and oxygen but have a higher proportion of hydrogen than carbohydrates. They are essential for energy storage, insulation, and forming cell membranes. Examples include triglycerides, phospholipids, and steroids.

3. Proteins: These are made up of long chains of amino acids. They have a wide range of functions including enzymatic activity, structural support, and hormone regulation. Examples include enzymes, antibodies, and collagen.

4. Nucleic Acids: These are complex molecules made up of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base. They are responsible for storing and transmitting genetic information. Examples include DNA and RNA.