Question

How do carbohydrates, proteins, and fats get digested in human beings?

Answer 1

Definition of digestion:

• Digestion is the process in which the food we ingest gets converted into simpler molecules. These simpler molecules can be easily absorbed by our bodies and enter into our blood. Blood then carries these simpler molecules to all the human body cells.

Important components of food:

• The food we eat contains three important components, which are considered vital nutrients. Those include carbohydrates, fats and proteins.

Digestion of Carbohydrates:

• Carbohydrates are broken down or digested in the mouth and the small intestine.

Carbohydrate digestion in the mouth:

• When we ingest food via the mouth, it gets chewed and combines with saliva produced by the salivary glands. The mixing of chewed food with saliva leads to bolus formation. Saliva contains an important enzyme called salivary amylase, which digests the carbohydrates present in the food. Complex carbohydrates (starch) get broken down into less complex forms during this process.
• The bolus then moves down via the esophagus and reaches the stomach. Bolus in the stomach is now known as chyme as it has mixed with the acidic contents inside the stomach. However, the stomach doesn't get involved in any further digestion of less complex carbohydrate forms. Less digested carbohydrates then enter into the small intestine.

Carbohydrate digestion in the small intestine:

• The less digested carbohydrates then move from the stomach to the initial part of the small intestine called the duodenum. In this response, the pancreas releases pancreatic juice, which contains pancreatic amylase. This amylase converts less digested carbohydrates into disaccharides, i.e., maltose, sucrose, and lactose.
• The small intestine also releases three important enzymes called maltase, sucrase, and lactase which further digest sucrose and lactose and maltose into simpler sugars. These simple sugars, i.e., glucose and fructose, enter the blood circulation via absorption.

Digestion of fats:

• Fats, which also represent an important component of nutrition, are mostly digested within the small intestine. When food enters the small intestine, the pancreatic juice is released by the pancreas, which contains an important enzyme called lipase. Lipase facilitates the breakdown of fats into fatty acids and glycerol. These broken down molecules are then absorbed in the small intestine and enter the blood circulation.

Digestion of proteins:

• Proteins present in the food are mostly digested in the stomach in the presence of the enzyme proteases. These enzymes break down protein molecules into individual amino acids. Amino acids are then absorbed within the small intestine and enter the blood circulation.