For carbs, the monomer is monsaccharides, for proteins, it is amino acids, for lipids/ fatty acids, it is glycerol (although many people think it doesn't have one), and for nucleotides it is nucleic acids.
Carbohydrates are a great source of energy, proteins are enzymes, fatty acids provide energy and hormones, and nucleotides are found in DNA, the most important molecule in your body.
