The Digestive system

Glucose Absorption

Glucose Absorption

The active transport used to absorb glucose (and other monosaccharides) is known as coupled active transport. This is where a facilitated diffusion protein is couple with an active transport protein.

    • The active transport protein, sodium potassium ATPase, works by constantly pumping potassium ions in and sodium ions out of the cell. It requires ATP to hydrolyse in order to function as the sodium ions are being pumped up their concentration gradient.
    • The sodium-glucose co-transporter protein is the facilitated diffusion protein. This consists of two binding sites: one for sodium ions and one for glucose. This protein uses diffusion, therefore passive transport. Due to the high concentration of sodium ions outside the cell both glucose and sodium are transported into the cell: the sodium ions down their concentration gradient and the glucose molecules against their concentration gradient.
    • The sodium gradient is restored by the sodium-potassium ATPase.
    • As glucose is pumped in its concentration increases. Glucose moves by facilitated diffusion into the villi tissue fluid and is transported by a glucose carrier protein, only located on the inner surface of epithelial cells.
    • It then diffuses through the gaps in the endothelial cells of the capillaries and is then transported into the blood to all cells in the body to be used in respiration.