glucose vs glycogen

glucose

noun
  • A simple monosaccharide (sugar) with a molecular formula of C₆H₁₂O₆; it is a principle source of energy for cellular metabolism. 

glycogen

noun
  • A polysaccharide that is the main form of carbohydrate storage in animals; converted to glucose as needed. 

How often have the words glucose and glycogen occurred in a corpus of books? (source: Google Ngram Viewer )