2. 4 Molecules containing covalently bonding carbon backbones are called organic compounds(including mainly alcohols, amines, aldehydes and ketones, carboxylic acids, sulfhydryls,.. etc. Most biomolecules are organic compounds 2.5 Carbon atoms have a characteristic tetrahedral arrangement of their four single bonds. Carbon-carbon single bonds have freedom of rotation, but not double nor triple bonds 2.6 No other chemical element has the capacity to form molecules of such widely different sizes and shapes or with such a variety of functional groups.2.4 Molecules containing covalently bonding carbon backbones are called organic compounds (including mainly alcohols, amines, aldehydes and ketones, carboxylic acids, sulfhydryls, … etc. Most biomolecules are organic compounds. 2.5 Carbon atoms have a characteristic tetrahedral arrangement of their four single bonds. Carbon-carbon single bonds have freedom of rotation, but not double nor triple bonds. 2.6 No other chemical element has the capacity to form molecules of such widely different sizes and shapes or with such a variety of functional groups