Digestion of Larger Insoluble Molecules

Digestion is the process where the body breaks down food into smaller, soluble substances that can be absorbed into the bloodstream.
Larger, insoluble molecules such as proteins, fats and carbohydrates need to be broken down into smaller, soluble molecules for the body to utilise them.
For proteins, these large molecules are broken down into smaller units called amino acids. This process is facilitated by enzymes, such as proteases, present in the stomach and pancreas.
Carbohydrates, like starch, are broken down into simple sugars, like glucose. This is done through the action of enzymes like amylase, which is found in the mouth and pancreas, and maltase, which is present in the small intestine.
Fats are broken down into glycerol and fatty acids by lipases. These enzymes are produced by the pancreas and work in the small intestine.
Enzymes are biological catalysts that speed up the breakdown of these larger molecules into smaller ones. They work best at specific conditions of temperature and pH.
The process of breaking down these larger molecules begins in the mouth, continues in the stomach and finally takes place predominantly in the small intestine.
The liver produces bile, which emulsifies fats to aid their digestion. This breaks the fat into smaller droplets, providing a larger surface area for the lipase to work on.
The digested, smaller soluble substances are then absorbed into the bloodstream through the wall of the small intestine. This process is called absorption.
Any undigested food is passed into the large intestine where water is reabsorbed back into the body. The remaining waste, or faeces, is stored in the rectum before being egested through the anus. This is the process of egestion.
It’s important to note that digestion is not the same as absorption. While digestion is about breaking down food, absorption is about moving digested food into the blood.

Please remember that diagrams, such as those of digestive system, may be very useful for understanding the sequence and location of digestion and absorption.