Question

Discuss how expression of transporters determines the metabolic activities of a cell. (Biochemistry)

Answer 1

Expression of transporter proteins determines cells metabolic activity by a variety of ways, one such example is transport of glucose molecules across the plasma membrane because glucose serves as primery source of metabolic energy for cells.

Transport of glucose molecules occurs mainly by three ways-

1) Passive movement by carrier proteins

2) Active transport by the use of ATP

3) Active transport by the use of energy deriven by proton pump

1) Passive transport of glucose by carrier proteins- Carrier proteins are responsible for the facilitated diffusion of sugars, amino acids, and nulceosides across the plasma membrae of most cells.

Kinetic studies indicates that glucose transporter functions by alternating between two conformational states. In first conformation, a glucose binding site faces outside the cell. The binding of glucose to this exterior site induces conformational changes in the glucose tansporter such taht glucose binding site now faces to the interior of cell. Glucose is now released in the cytosol and transporter returns to its original conformation.

2) Transport by the use of ATP as energy source involves the use of ATP molecules by transporter protein for glucose transport such transprt proteins are present on the cells of intestinal lining.

3) Transport by the use of proton pump as energy source- such type of trnsport proteins are mainly resposible for glucose absorption from intestinal lining. The cells of intestinal lining uses the energy derived by proton gradient made by sodium potassium pump. These transporter proteins transports coordinately one Na⁺ and one glucose molecule into the cell. The flow of sodium ions down their electrochemical gradient provides energy for this transport. In this way cells of intestinal lining are able to store high concentration of glucose, which is than transported to underlying connective tissue.