Suggest how the active transport of glucose out of the cell and into the bloodstream helps with the absorption of glucose from the small intestine. (2 marks)
To understand how the active transport of glucose out of the cell helps with the absorption of glucose from the small intestine, we need to understand a few concepts.
Active transport is a cellular process that requires energy in the form of ATP (adenosine triphosphate) to move molecules against their concentration gradient. In the case of glucose absorption, active transport is crucial as the concentration of glucose is generally higher inside the small intestine than in the bloodstream.
Here's how the active transport of glucose out of the cell and into the bloodstream aids in glucose absorption from the small intestine:
1. Sodium-Glucose Cotransporter (SGLT): The small intestine lining contains specialized proteins called sodium-glucose cotransporters (SGLT). These SGLT proteins actively transport glucose from the lumen of the small intestine into the epithelial cells lining the intestine.
2. Energy Requirement: This active transport process requires the energy provided by ATP. The ATP is produced by the mitochondria within the epithelial cells of the small intestine.
3. Concentration Gradient: The concentration of sodium ions (Na+) inside the epithelial cells is typically lower than in the small intestine lumen. By actively transporting Na+ ions out of the cell and into the bloodstream using ATP-driven sodium-potassium pumps, a concentration gradient is established.
4. Coupled Transport: The SGLT protein helps transport glucose out of the lumen by utilizing the energy stored in this created concentration gradient. It facilitates the active transport of glucose against its concentration gradient from the intestine into the epithelial cells, using the energy released by the downhill movement of sodium ions.
5. Facilitated Diffusion: Once glucose enters the epithelial cells, it can passively diffuse across the basal side (opposite to the intestinal lumen) of the cell membrane through glucose transporters such as GLUT2. These transporters enable the diffusion of glucose from the epithelial cells into the bloodstream due to the concentration gradient.
By using active transport mechanisms such as SGLT, the small intestine maximizes the absorption of glucose. This process ensures that glucose is efficiently transported from the lumen of the small intestine into the bloodstream, allowing it to be distributed and used by cells throughout the body.