Carbohydrates:

Carbohydrates are the human body’s key source of energy, providing 4 calories of energy per gram. When carbohydrates are broken down by the body, glucose is produced.

Carbohydrates are available in wide variety of foods, for example: cereals, fruits (especially dates), honey, milk, sugar, beet, potato, and sugarcane.

Digestion of Carbohydrates in Humans:

• Carbohydrates digestion begins in the mouth only and continues up to the stomach and small intestine.
• Salivary amylase present in the saliva, amylase and maltase present in the small intestine helps in the digestion of carbohydrates.

Proteins:

Proteins are the chief builders of the body. They are complex molecules made up of carbon, hydrogen, oxygen and nitrogen. Proteins are used to synthesize enzymes (pepsin, trypsin), hormones (insulin, adrenaline).

Proteins are present in cereals, groundnuts, beans, pulses, fish, eggs, meat, milk, cheese etc.

Digestion of Proteins in Humans:

• Protein digestion mainly takes place in stomach.
• Gastric glands of the stomach secrete enzymes such as pepsin which digests the proteins.

Fats:

Fats are nutrients in food that the body uses to build cell membranes, nerve tissue (including the brain) and hormones. The body also uses fat as fuel. It is essential to eat some fats, though it is also harmful to eat too much. The fats you eat give your body energy that it needs to work properly. During exercise, your body uses calories from carbohydrates you have eaten.

The common fats are butter, ghee, cheese, meat, egg yolk, milk, nuts etc.

Digestion of Fats in Humans:

• Fats digestion starts in stomach.
• Gastric glands of the stomach secrete gastric lipase is present which helps in the digestion of fats.
• In the small intestine, pancreatic lipase is present which helps in the breakdown of the emulsified fats.