The process of harvesting energy from carbohydrates begins with digestion, which involves converting food into smaller molecules through both mechanical and biochemical breakdown. Mechanical breakdown refers to the physical actions, such as chewing and grinding, that reduce food into smaller pieces. Biochemical breakdown, on the other hand, utilizes hydrolysis to further decompose larger molecules into smaller ones.
Initially, the enzyme salivary alpha-amylase plays a crucial role in this process by hydrolyzing starch and glycogen into smaller polysaccharides and maltose. Polysaccharides are polymers composed of multiple glucose molecules linked by glycosidic bonds, while maltose is a disaccharide formed from two glucose units connected by a glycosidic linkage. Additionally, oligosaccharides, which consist of 3 to 10 monosaccharides, are produced through the hydrolysis of glycogen and starch; these are sometimes referred to as dextrins.
As digestion progresses, the acidic environment of the stomach inactivates salivary alpha-amylase, effectively halting carbohydrate digestion. Although the stomach does not secrete enzymes for carbohydrate hydrolysis, it plays a significant role in inactivating this enzyme. The next phase occurs in the small intestine, where further hydrolysis leads to the production of a mixture of monosaccharides, including glucose, fructose, and galactose. Understanding these processes is essential for grasping the fundamentals of carbohydrate metabolism.