GLUT4 transporters are

a. stored in cytoplasmic vesicles and found in adipose and skeletal musles

b. only found in adipose and skeletal muscles

c. only inserted into the plasma membrane by endocytosis

d. only stored in cytoplasmic veesicles

The correct answer is option a.

Explanation:

The GLUT-4 or glucose transporter type 4 refers to a protein encoded in humans. It is the insulin-regulated glucose transporter, which is found mainly in the striated muscles and adipose tissues. The increased level of insulin leads to the uptake of glucose into the cells. When insulin combines with the membrane receptors the GLUT-4, which is stored in the cell in the form of transport vesicles gets quickly assimilated into the plasma membrane. When the concentration of insulin becomes low, the majority of GLUT-4 gets sequestered in the intracellular vesicles in the fat and muscle cells.