Amino acids are the chemical units or "building blocks" that make up proteins. Protein provides the structure for all living things. Next to water, protein makes up the greatest portion of our body weight. Proteins make up the muscles, ligaments, tendons, organs, glands, nails, hair and are essential for bone growth. Enzymes and hormones that catalyze and regulate all bodily processes are protein. Dietary amino acids are classified as "essential" or "non-essential". Essential amino acids cannot be manufactured by the body and must be supplied in the diet or ill-health results. The non-essential amino acids are reassembled as hormones, enzymes, neurotransmitters (chemical messengers), antibodies and nutrient carriers.