How are different foods broken down in the digestive tract?

Different foods are broken down in the digestive tract through mechanical and chemical processes involving enzymes and stomach acids.

The digestive process begins in the mouth, where food is mechanically broken down by chewing and chemically broken down by enzymes in saliva. Salivary amylase, for instance, starts the breakdown of carbohydrates into simpler sugars. The food then travels down the oesophagus into the stomach, where it is further broken down by the mechanical churning action of the stomach muscles and the chemical action of stomach acid and enzymes. Pepsin, a stomach enzyme, begins the breakdown of proteins into smaller peptides.

The partially digested food, now a thick liquid called chyme, moves into the small intestine. Here, it is broken down further by a variety of enzymes. Pancreatic amylase continues the breakdown of carbohydrates, while proteases like trypsin and chymotrypsin continue the breakdown of proteins. Lipases, also secreted by the pancreas, begin the breakdown of fats into fatty acids and glycerol. These enzymes work best in the alkaline environment provided by bicarbonate ions, also secreted by the pancreas.

The final stages of digestion occur in the large intestine, where bacteria break down any remaining carbohydrates and proteins, producing gases and a few vitamins as by-products. The large intestine also absorbs water and electrolytes from the remaining undigested food matter, transforming it into faeces.

In summary, the breakdown of different foods in the digestive tract involves a combination of mechanical and chemical processes. Different enzymes, working in different parts of the digestive tract and under different conditions, break down carbohydrates, proteins, and fats into their constituent parts, which can then be absorbed and used by the body.