Histology Embryology ° Chemica| digestion Complex food molecules(carbohydrates, proteins and lipids) broken down into chemical building blocks(simple sugars, amino acids and fatty acids and glycerol) Carried out by enzymes secreted by digestive glands into lumen of the alimentary canal• Chemical digestion --- Complex food molecules (carbohydrates, proteins and lipids) broken down into chemical building blocks (simple sugars, amino acids, and fatty acids and glycerol) --- Carried out by enzymes secreted by digestive glands into lumen of the alimentary canal