Middle back pain is any type of pain or discomfort in the area between your upper and lower back. Health care professionals refer to this area as the lower thoracic area or lower thoracic spine. The upper thoracic area or upper thoracic spine makes up part of the upper back.
Amino Acids. Amino acids are the monomers of proteins. They have a positively-charged amino group on one side and a negatively-charged carboxyl group on the other. Attached to the central carbon is a variable group called the 'R' group. This group is different for each amino acid. There are 20 amino acids in human cells.
1 For lipids (Diglycerides, triglycerides)*, the monomers are glycerol and fatty acids. 2  For proteins (Polypeptides), the monomers are amino acids.  For Nucleic acids (DNA/RNA), the monomers are nucleotides which is made of a pentose sugar, a nitrogenous base and a phosphate group.