Final answer:
The regulation of glycogen metabolism varies between liver and muscle cells, with liver cells exporting glucose to the blood and being insulin-sensitive. Muscle cells use glycogen internally for energy, do not export glucose, and are regulated differently by hormones such as adrenaline.
Step-by-step explanation:
The regulation of glycogen metabolism differs between liver and muscle cells. In muscle cells, glycogen provides energy directly to the cell during periods of exertion, which makes the muscle less sensitive to insulin when compared to liver cells. Glycogen phosphorylase, the enzyme involved in breaking down glycogen, is in its active state when phosphorylated in muscle cells, whereas glycogen synthase, the enzyme for synthesizing glycogen, is deactivated when phosphorylated.
Liver cells, on the other hand, play a key role in maintaining blood glucose levels. Liver glycogen can be broken down and the glucose exported to the bloodstream to supply energy to other cells. In response to insulin, liver cells can also increase their storage of glycogen. While muscle cells do not export glucose into the bloodstream since the glucose remains as glucose-6-phosphate (G-6-P) for internal use. Also, muscle glycogenolysis is regulated by adrenaline through a cAMP-dependent pathway, leading to the activation of glycogen phosphorylase, which helps to fuel the muscle during the 'fight or flight' response.