Sugars are hydrocarbons with hydroxyl groups replacing at least one of the hydrogens on each carbon. Fatty acids are hydrocarbons of about 20 carbons with a carboxyl group at one end. Unsaturated fatty acids have one or more double bond between some of the carbons. Triglycerides are combinations of three fatty acids, usually with glycerol as the backbone connecting them together. Weird lipids like cholesterol have ring structures and form the steroid hormones .
Amino acids are carbons with a hydrogen, amino, and carboxyl groups, and a variable group.
Proteins are made of almost every imaginable linear combination of amino acids, connected into polypeptides by amino-carboxyl peptide bonds . Conformation or shapes of proteins are determined first by the primary linear structure of amino acids, then their secondary structure of regions of alpha helix and pleated sheets, then their tertiary structures of overall shape, and finally sometimes their quaternary combinations of different subunits. Nucleotides are the monomers of the spectacular polymers DNA and RNA, composed of three parts, a ribose sugar , a phosphate , and a ringed base . They can also function individually, for example, ATP and co-enzymes like NAD in metabolism, or cyclic AMP in hormone signalling. Click here to return to the Biology 104 home page.