Answer:
Insulin.
Step-by-step explanation:
Insulin allows glucose to be transported across cell membranes for use within the cell.
Insulin is a hormone secreted by the pancreas that controls the concentration of glucose in the blood. It stimulates cells to absorb and use glucose as a source of energy.
Insulin also decreases lipolysis, and increases the transport of amino acids in cells.
Insulin has many functions, but the most important is the control of the concentration of glucose.