Question

Where does the chemical digestion of carbohydrates begin in the body?

Answer 1

Breakdown of large food molecules (i.e., proteins, fats, polysaccharides, nucleic acids) into smaller ones (I.e., amino acids, fatty acids, monosaccharides, nucleotides) is called digestion. Chemical digestion is the enzyme-mediated breakdown of large macronutrients into smaller molecules. Carbohydrates are taken mainly in the form of animal carbohydrates (glycogen) and plant carbohydrates (amylose). Amylose is not highly branched and mainly consists of a long chain of glucose linked by alpha 1:4 linkages.

Complete answer:
1. From the mouth to the stomach:
In the mouth, the mechanical and chemical digestion of carbohydrates begins. Chewing or masticating crumbles the carbohydrate into smaller and smaller pieces. The saliva secreted by salivary glands coats the food particles. Salivary amylase, an enzyme of saliva, breaks the bond between the monomeric sugar units of disaccharides, oligosaccharides, and starches. The salivary amylase breaks down amylose and amylopectin into dextrins and maltose. Only five percent of starches are broken down in the mouth. Amylase enzyme doesn’t function in the acidic condition of the stomach therefore, no chemical breakdown of carbohydrates occurs in the stomach. But the mechanical breakdown is still undergoing- the strong peristaltic contraction of the stomach mixes the carbohydrate into chyme (a more uniform mixture).
2. From the stomach to the small intestine:
The chyme gradually enters the upper part of the small intestine. When it enters, the pancreas releases the pancreatic juice through a duct. The pancreatic amylase of the pancreatic juice starts the breakdown of dextrins into shorter carbohydrate chains. Intestinal cells that line the villi also secrete enzymes. These enzymes are sucrose, maltase, and lactase. Sucrose is broken down into glucose and fructose by the enzyme sucrase. Maltose is broken down into two units of glucose by the enzyme maltase. Lactase breaks down lactose into glucose and galactose.

Note:
People who do not have enough lactase enzymes suffer from lactose intolerance, a condition in which lactose is not sufficiently broken down. The undigested lactose is broken down by bacteria in the large intestine. The bacterial digestion of lactose produces gases that lead to the symptoms of bloating, diarrhea, and abdominal pain.