Name: Process of Digestion in Human Beings
Uploaded: 2019-07-19
Duration: 5 min 25 s
Description: Hungry? What is the process by which our body processes food? Let's go on a food trip through the human digestive system and learn how our body digests food.

Question

A person had roti and dal for his lunch. Trace the changes in those during its passage through the alimentary canal.

Accepted Answer

Roti mainly contains carbohydrate and fibers, while dal contains protein. Dal may also contain fat because of the addition of oil or ghee during cooking. Following changes would happen in these food items during their passage through the alimentary canal.

Oral Cavity:

In the oral cavity, food is chewed so that it can change into a bolus. Saliva is mixed with food. Saliva makes it easier to swallow the food. Moreover, salivary amylase in saliva digests starch. Starch is converted into maltose during this process.

Starch $\to_{p H 6.8}^{S a l i v a r y A m y l a s e}$ Maltose

Stomach:

After the buccal cavity, the food reaches the stomach through the oesophagus. No digestion occurs in the oesophagus. In the stomach, food is converted to chyme. Hydrochloric acid gets mixed with the food. It provides acidic pH for optimum activity of pepsin. Partial digestion of protein takes place in the stomach.

Protein $+$ Pepsin $\to$ Peptones $+$ Proteoses

Small Intestine:

Pancreatic juice contains pancreatic amylase. Amylase in pancreatic juice converts polysaccharides into disaccharides. This step shows further processing of carbohydrates from the roti.

Polysaccharides (starch) $\overset{A m y l a s e}{\to}$ Disaccharides

Chymotrypsin from pancreatic juice digests peptones and proteoses into dipeptides.

Fats $\overset{L i p a s e s}{\to}$ Diglycerides $\to$ Monoglycerides

The enzymes of the succus entericus end products of the above reactive to simple absorbable form. The simple absorbable form of roti and dal are:

Dipeptides $\overset{D i p e p t i d a s e s}{\to}$ Amino acids

Maltose $\overset{M a l t a s e}{\to}$ Glucose $+$ Glucose

Lactose $\overset{L a c t a s e}{\to}$ Glucose $+$ Galactose

Sucrose $\overset{S u c r a s e}{\to}$ Glucose $+$ Fructose

Di and Monoglycerides $\overset{L i p a s e s}{\to}$ Fatty acids $+$ Glycerol

Once all the nutrients are converted into simple substances, the simple substances are absorbed by the walls of the small intestine. After that, undigested food is sent to the large intestine and finally to the rectum.

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