Final answer:
4) GLUT4 is the glucose carrier activated by insulin or exercise, playing a critical role in glucose uptake into cells, especially in insulin-responsive tissues like muscle and adipose tissue.
Step-by-step explanation:
The glucose carrier that is activated by insulin or exercise is called GLUT4, as indicated in various sources. This protein is stored in vesicles within the cell, and upon the binding of insulin to insulin receptors or through mechanisms initiated during exercise, a cascade of events is triggered, resulting in the fusion of GLUT4-containing vesicles with the plasma membrane.
Consequently, this allows glucose to be transported into the cell. Importantly, in the presence of insulin, GLUT4 facilitates rapid movement and insertion into the plasma membrane to increase the rate of glucose uptake from the blood into insulin-responsive tissues such as muscle cells and adipose tissue. While insulin also stimulates glycogen synthesis through IRS-1, GLUT4 specifically is responsible for the initial uptake of glucose into these cells.
The role of GLUT4 in glucose metabolism is crucial, especially when considering conditions like diabetes, where the regulation of this transporter may be compromised, leading to improper glucose homeostasis.
Therefore, understanding which GLUT protein is insulin-sensitive holds significant importance for both physiological understanding and clinical applications. In summary, GLUT4 is the correct answer to the question of which glucose transporter is activated by either insulin or exercise.