Draft: Muscle vs. liver cells

Muscle cells use a variety of fuel sources: fatty acids at rest and glucose during exertion, at least initially. Muscle cells also vary widely in their energy demands and use glycogen stores only for themselves, not sharing with other cells. Glycogen breakdown overly exceeds glycogen synthesis by 300-fold, and they do not respond to glucagon. Muscle cells also do not perform gluconeogenesis, fatty acid synthesis, or ketogenesis. On the other hand, liver cells are very important for fatty acid homeostasis, performing triacylglycerol formation and fatty acid synthesis. They are also the primary site of ketone body synthesis and directly regulate blood glucose levels in response to hormones. Liver cells are also important storage sites for glycogen with equal rates of synthesis and breakdown of glycogen. Like muscle cells, liver cells use a variety of fuel sources that change depending on conditions.