How are glucose molecules absorbed in the gut?

Food consists of many types of molecules, these are: polysaccharides (a chain of single molecular units); dissacharides (a pair of single molecular units) and monosaccharides (the individual units themselves). Glucose can be present in a polysaccharide chain (e.g. starch), a dissacharide (e.g. maltose) and a monosaccharide (glucose itself). Before any absorption takes place, the poly- and di-saccharides first need to be broken down, by their associated enzymes, into glucose.

Glucose enters the small intestine and is absorbed by a process called "co-transport". Co-transport is when two molecules are transported across a membrane at the same time through a carrier protein. In this case, it is glucose with a sodium ion. The sodium moves into the cell through the sodium-glucose cotransporter protein, carrying glucose along with it. This process requires energy (as ATP), which is produced by the sodium/potassium pump. The glucose is now in the cell and is phosphorylated to maintain the flow of glucose into the cell. This glucose molecule now moves into the blood through a glucose carrier protein.