Final answer:
Carbohydrates are digested into monosaccharides by enzymes such as amylase, maltase, lactase, and sucrase, and absorbed in the small intestine through secondary active transport for glucose and galactose, and facilitated diffusion for fructose. These simple sugars are then transported into the bloodstream, regulated by hormones insulin and glucagon.
Step-by-step explanation:
During digestion, carbohydrates are initially broken down into smaller molecules through the action of enzymes such as salivary amylase in the mouth and pancreatic amylase in the small intestine. The resulting disaccharides are further digested into monosaccharides by enzymes like maltase, lactase, and sucrase. Once carbohydrates are broken down into monosaccharides, which are simple sugars such as glucose, fructose, and galactose, they are ready to be absorbed.
Absorption occurs primarily in the small intestine, where glucose and galactose are absorbed through secondary active transport linked to sodium ions, and fructose is absorbed via facilitated diffusion. These monosaccharides enter the epithelial cells lining the small intestine and are then transported into the bloodstream through the intestinal capillaries, where they can be used as energy or stored for later use. The hormones insulin and glucagon help regulate the uptake and release of these sugars into the cells.
Importantly, all digestible dietary carbohydrates are absorbed, while indigestible fibers are excreted in the feces. This efficient absorption process in the small intestine is estimated to absorb about 120 grams of monosaccharides per hour, ensuring the body has a continuous supply of energy.