Steps for human absorption of carotene

When animals consume carotene in their daily diet, it undergoes a process in the gastrointestinal tract where digestive enzymes separate it from its protein complex. Subsequently, in the duodenum, bile emulsifies carotene with other esters, leading to the formation of chyle particles.

As chylomicrons make their way to the brush border of intestinal absorption cells, they are taken up by the mucosal epithelial cells of the intestine for absorption. This process is essential for efficient absorption of nutrients from the diet.

Once the carotene is absorbed into the small intestinal epithelial cells, it is quickly transported to one side of the membrane. The carotene undergoes cleavage by dioxygenase, resulting in the formation of vitamin A. This process takes place either in the middle or on one side of the cell to fulfill the body's requirements for this essential nutrient.

Before it reaches the liver, esterase aids in the absorption of carotene by extrahepatic tissues. Any remaining carotene is then transported to the liver by density lipoprotein, together with chylomicrons, through the lymph and blood.

After being consumed, carotene is processed by the liver, where it can either be stored within the liver itself or released into low-fat protein. This low-fat protein, along with high-density lipoprotein, carries the carotene to tissues outside of the liver, such as the skin and eyes, where it is then stored. Essentially, carotene travels from the liver to extrahepatic tissue for storage purposes.