Fate of the Digested Products of Fats, Carbohydrates and Proteins

Digestion breaks down large complex molecules into smaller ones, enabling the body to absorb them. This process occurs for proteins, carbohydrates and fats.
The end-product of protein digestion is amino acids. These are absorbed through the lining of the small intestine (the ileum) into the bloodstream and transported to the liver. The liver plays a significant role in the metabolism of these amino acids, including deamination (removal of the amino group), transamination (transfer of the amino group) and protein synthesis.
The final products of carbohydrate digestion are monosaccharides, such as glucose, fructose and galactose. The small intestine absorbs these simple sugars. Once in the bloodstream, they are carried to the liver, where they are either used straightaway for energy or converted into glycogen for storage.
Digestion of fats results in fatty acids and glycerol. These are also absorbed in the ileum of the small intestine. Once in the bloodstream, they are transported to adipose tissue for storage or to different tissues where they can be used for energy production.
Fatty acids and glycerol cannot dissolve in the bloodstream, hence they form lipoproteins with proteins for ease of transport.
It’s important to emphasise that the absorbed products of digestion are used for different purposes, such as immediate energy need, growth, cell repair and maintenance of body functions.
Glucose, for example, is an essential energy source and the brain exclusively uses it as an energy supply.
Amino acids are used to build proteins, which are needed for growth and repair of body tissues, as well as synthesis of enzymes, hormones, antibodies etc.
Fatty acids and glycerol are major components in adipose tissue and are an important storage form of energy. When needed, these are broken down for energy or for metabolic needs in the liver.