Carbohydrate digestion and metabolism break down simple and complex carbohydrates from food into saccharides (i.e., sugars) for the body to use as energy. Carbohydrate digestion starts in the mouth during mastication, or chewing. The masticated carbohydrates remain intact in the stomach. Digestion resumes in the duodenum of the small intestine, where pancreatic alpha-amylase and brush border enzymes of the microvilli convert complex carbohydrates to monosaccharides. Finally, the monosaccharides...

Every plant cell has a cell wall that protects the cell, provides structural support, and gives the cell shape. Cellulose, the main structural component of the plant cell wall, makes up over 30% of plant matter. It is the most abundant organic compound on earth.  Cellulose is an unbranched polysaccharide composed of linear chains of glucose molecules linked by β (1→4) glycosidic bonds.
As a cell matures, its cell wall specializes according to its type. For example, the parenchyma cells of...

Carbohydrates are essential macronutrients that serve as the body's primary energy source. Their digestion begins in the mouth, where salivary amylase partially breaks down complex carbohydrates such as starch into smaller oligosaccharides. This mechanical and enzymatic activity prepares carbohydrates for further processing in the gastrointestinal tract.
After being swallowed, the partially digested carbohydrates mix with gastric secretions in the stomach. However, the acidic environment...

Carbohydrates, proteins, and fats are the primary macronutrients in the human diet. However, carbohydrates are the most favored source of energy in the body. They can be found in a wide variety of foods, including whole grains, fruit, and vegetables, in various forms, such as sugars, starch, and dietary fiber. Based on their structure, carbohydrates are classified into three main classes— monosaccharides, disaccharides, and polysaccharides. The body's cells can only utilize simple...

Carbohydrates are polymers composed of molecules containing atoms of carbon, hydrogen and oxygen. One gram of carbohydrate can provide four kilo-calories of energy, which makes it the most efficient instant energy source.
Starch accounts for approximately 60% of the carbohydrates consumed by humans. Since amylase enzymes cannot function in the stomach's acidic environment, starch can only be digested in the mouth and small intestine. Simple sugars are found naturally in milk and fruits in the...

The human body contains a monogastric digestive system. In a monogastric digestive system, the stomach only contains one chamber in which it digests food. Several other animal species also have monogastric digestive systems, including pigs, horses, dogs, and birds. This chapter, however, focuses on the human digestive system.