Is a key element found in all carbohydrates, lipids, proteins, and nucleic acids?

Carbon is a key element found in all carbohydrate, lipids, proteins and nucleic acids, which are all organic macromolecules.

The fundamental component of all these macromolecules is carbon. The carbon atom has the unique ability to  form covalent bonds with as many as four different atoms, making it the best or ideal element to form the backbone or  basic structural component  of the macromolecules.

Carbon easily bonds with non - metallic  elements and due to this, it is termed often as the building block of life.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.