USE OF FOOD IN THE BODY

USE OF FOOD IN THE BODY

Use of food in the body involves three processes --- digestion, absorption and utilization of nutrients in the body.

Digestion is the process, which releases many nutrients in the forms the body can use, by breaking up food in the intestinal tract.

Absorption is the process which carries these nutrients into the circulation system and delivers them to the cell.

Utilization: Cell is the functional unit of life. Hence a large number of the chemical reactions in the cell utilize the nutrients absorbed to produce materials needed for our existence.

Mechanical processes involved in digestion include chewing of food, swallowing of food, churning action in the stomach and rhythmic contraction of the intestinal tract. 

The digestive tract consist of mouth, Esophagus, Liver, Gall bladder, Stomach, Pancreas, Longitudinal muscle, Circular muscle, Duodenum, Jejunum, Large intestine, Ileum, Small intestine, Appendix, Anal Sphincter, Rectum.

Chewing of food reduces the food particles in size, mixes these with saliva and dilutes it with water, so that it is easy to swallow. The food swallowed is mixed with enzymes and acid by the churning action in the stomach. Further the rhythmic contraction of the intestine, help to break the food into small particles and move the food mass forward through the digestive tract.

Chewing of food reduces the food particles in size, mixes these with saliva and dilutes it with water, so that it is easy to swallow. The food swallowed is mixed with enzymes and acid by the churning action in the stomach. Further the rhythmic contraction of the intestine, help to break the food into small particles and move the food mass forward through the digestive tract.

Chemical reactions in digestion process: The first reaction is hydrolysis or splitting with the help of water, Carbohydrates, fats, and proteins break up with the addition of water into smaller molecules, which the tissues can use.

The chemical reactions are accelerated by enzymes, which are secreted in the mouth, stomach and small intestine. Enzymes are living catalysis, that increase the speed of biological reactions, without being a part of compound formed. The enzymatic reactions, which take place in the digestion processes are presented in the table.

As you may know, enzymes are proteins by nature. Their name indicates substance on which they can act, for example, sucrose act on sucrose. Enzymes are specific in their actions. An enzyme, which hydrolyses protein, will not act on starch. Each enzyme acts optimally at a certain pH, e.g., amylase acts only in alkaline medium.

Someone enzymes need another group, known as a coenzyme, to be attached to it to aid their function. For example, B-vitamin serve as a coenzymes in the reactions, which release energy from glucose. In enzyme reactions, mineral elements are essential as cofactors. Thus normal body metabolism is dependent on the presence of appropriate enzymes, coenzymes and cofactors specific to each reaction.

The digestive enzymes are only one group of a large number that are essential to regulate body processes. Other enzymes are present in various tissues of the body and help in the utilization of food that has been absorbed.

Carbohydrates

The digestion process begins with chewing the food in the mouth. The enzyme ptyalin starts the digestion of starch in the mouth. It hydrolyses stars to dextrin, isomaltose and maltose in  neutral or alkaline pH in the mouth. The food tastes sweet due to these products of hydrolysis. The activity of amylase continues in its movement from the mouth to the upper part of the stomach. But as soon as the food mass comes in contact with hydrochloric acid secreted there, this action ceases. Very little digestion of carbohydrates occurs in the stomach as the pH is unfavorable.

The food mixed with gastric juice forms a semi-fluid mass called chime. It takes about three to five hours to form chime. Small portion of chime are released through the pyloric sphineter into the duodenum, the first part of the small intestine.

Proteins: Digestion of proteins starts in the stomach, which serves as a storehouse, where some protein hydrolysis begins. Milk is clotted by a special enzyme rennin and acid is added.

Lipids: The stomach lipase does act on emulsified fats in milk, cream, butter, and egg yolk, but most of the hydrolysis of fats takes place in the small intestine.