Question

How can we use protein as an energy source if carbohydrates and fat are not available? What are the metabolic pathways and organs involved.

Answer 1

Carbohydrates, proteins and lipids are the major components and fuel of energy. Among these carbohydrate acts as the major source of our body. Protein provides energy of 4 kcal and it is very important for structure and support for cells. It is not stored in our body and hence it is converted to other types like triglycerides and is deposited in our body. If the carbohydrates or lipids are deficient, body starts to use for energy purposes. The enzymes produced by pancreas trypsin, chymotrypsin and elastase helps in protein digestion (proteolysis) and breaks down into amino acid units. The amino acids are used to create proteins. Amino acids are used as a source of energy mainly in starving period. The processing of amino acids produces many intermediates which can be used for the ATP production through Krebs cycle. The excess amino acids are decomposed and converted into urea through the process of urea cycle which excreted from body through urine.