Upon digestion, the dietary elements are broken down into small units for absorption and from there the product of digestion pass through the circulation to the rest of the body.
Dietary carbohydrates are a rich source of Glucose, which is the most preferred fuel for metabolic energy. It is delivered to the liver via the portal vein. Oxidation of Glucose (by glycolysis/ anaerobic ) by tissues meets the immediate energy needs. The excess glucose is immediately converted into glycogen in liver and muscles. Glucose is also metabolised to triacylglycerol in the liver and exported for storage in adipose tissue in response to high glucose stimulated by insulin (lipogenesis).
Similarly, for absorption Dietary proteins, are broken down to amino acids. The small intestine uses amino acids for fuel, but most travel to the liver via the portal vein. There, they are used for protein synthesis or, if present in excess, oxidized to produce energy or converted to glycogen for storage. They may also be converted to glucose or triacylglycerols for export, depending on conditions.
There is no dedicated storage depot for amino acids; whatever the liver does not metabolize circulates in peripheral tissues to be catabolized used for protein synthesis.