text: How many amino acids are there?  These are the "monomer" units, although they're not true monomers since they don't repeat much.  \n\n"R" symbolizes "other stuff" bonded to the peptide functionality.  Different amino acids have different atoms for "R".  \n\nCalories per gram depends on the specific material.  I would expect fats to contain the most, since they are mostly C and H, followed by carbohydrates, followed by proteins.  I could be wrong, though.