Here's why:
* Carbohydrates are the primary source of energy for living organisms. They are made up of simple sugars (monosaccharides) like glucose and fructose, which can be linked together to form complex carbohydrates (polysaccharides) like starch and cellulose.
* Lipids (fats and oils) also contain CHO, but they have a higher proportion of hydrogen and a lower proportion of oxygen compared to carbohydrates.
* Proteins are made up of amino acids, which contain CHO, but they also include nitrogen (N).
* Nucleic acids (DNA and RNA) contain CHO, but they also include nitrogen (N) and phosphorus (P).
So, while other biomolecules contain CHO, carbohydrates are the primary group defined by this elemental composition.
