Final answer:
When extracellular glucose concentration is higher than within the cells, glucose is taken in through active transport. This process is energy-dependent and works against the concentration gradient with the help of insulin, which promotes cellular uptake and storage.
Step-by-step explanation:
When the concentration of extracellular glucose is higher than the concentration already stored in the cells, the process used is active transport. This process involves glucose binding to a carrier protein along with two Na+ ions. It is through this compound mechanism that glucose is efficiently transported into the cell against a concentration gradient, which requires the expenditure of energy in the form of ATP.
Once inside these cells, glucose may be promptly converted to glucose-6-phosphate to maintain the concentration gradient. The presence of insulin stimulates cells to take in glucose for use as immediate energy through the process of glycolysis or for storage as glycogen in liver and muscle tissue. The regulation of blood glucose levels is a complex process influenced by hormones such as insulin and glucagon, and specifically targets cells like skeletal muscle cells and adipose cells for glucose uptake after a meal, when blood glucose levels rise.
Overall, active transport is essential for maintaining glucose homeostasis, especially in situations where glucose must be absorbed despite opposing concentration gradients.