How does the digestive system break down carbohydrates?

The digestive system breaks down carbohydrates through enzymatic actions starting in the mouth and ending in the small intestine.

The process of carbohydrate digestion begins in the mouth. Here, the enzyme salivary amylase, present in saliva, starts to break down complex carbohydrates, such as starch, into smaller chains of glucose molecules called maltose. This enzymatic action is facilitated by the mechanical action of chewing, which increases the surface area of the food for the enzymes to act upon.

The partially digested carbohydrates then move down the oesophagus and into the stomach. However, the stomach does not play a significant role in carbohydrate digestion. The acidic environment in the stomach inactivates the salivary amylase, halting the breakdown of carbohydrates temporarily.

The next stage of carbohydrate digestion occurs in the small intestine. Here, the pancreas releases pancreatic amylase into the small intestine. This enzyme continues the breakdown of complex carbohydrates into maltose. Additionally, the cells lining the small intestine produce enzymes called disaccharidases. These enzymes, including maltase, sucrase, and lactase, break down the disaccharides maltose, sucrose, and lactose into their respective monosaccharides: glucose, fructose, and galactose.

The monosaccharides are then absorbed through the walls of the small intestine and into the bloodstream. This absorption process is facilitated by transport proteins in the cell membranes of the intestinal cells. Once in the bloodstream, these monosaccharides can be transported to the cells of the body where they can be used for energy.

In summary, the digestive system breaks down carbohydrates through a series of enzymatic actions. These enzymes, produced by the salivary glands, pancreas, and cells of the small intestine, progressively break down complex carbohydrates into simpler sugars that can be absorbed and used by the body. This process is a crucial part of how the body obtains and utilises energy from food.