Carbohydrates that reduce Fehling's or Benedict's reagent are known as reducing sugars. All monosaccharides, whether aldose or ketose, are reducing sugars. Some 22 amino acids are commonly found in animals and more than 100 less common forms are found in nature, chiefly in plants. When two or more amino acids are joined together, they are known as peptides . Each protein is characterised by a unique and invariant amino acid sequence.
Proteins are essential to all living organism.
Many different proteins are found in the cells of living organisms. As enzymes they regulate all aspects of metabolism.