Carbon forms the framework of nearly all biological molecules primarily because a carbon atom can do which of the following?

Core Concept

With four valence electrons, carbon completes its octet by sharing electrons in four covalent bonds. This tetravalency lets carbon link to other carbons and to hydrogen, oxygen, nitrogen, phosphorus, and sulfur, producing straight chains, branched skeletons, rings, and double-bonded sites of diverse geometry. Carbon-carbon bonds are stable in aqueous solution at life-compatible temperatures yet remain reactive enough to be remodeled. No other common element combines this bonding versatility with comparable stability, which is why carbohydrates, lipids, proteins, and nucleic acids all rest on carbon frameworks.