How are carbohydrates defined in terms of their composition?

Carbohydrates are organic compounds that are primarily composed of carbon, hydrogen, and oxygen. The defining characteristic of carbohydrates is their specific ratio of these elements, which is typically 1:2:1. This means that for every carbon atom, there are two hydrogen atoms and one oxygen atom. This ratio is seen in simple sugars, like glucose (C6H12O6), which follows the pattern, with six carbon atoms providing twelve hydrogen atoms and six oxygen atoms.

This 1:2:1 composition is essential for identifying carbohydrates and differentiating them from other macromolecules. For instance, proteins contain nitrogen and have a very different structure and function. Similarly, lipids do not follow the same elemental ratio as carbohydrates and are primarily made of long hydrocarbon chains. Thus, the defining composition of carbohydrates allows them to play unique roles in energy storage, structural components, and cellular signaling in biological systems.