Final answer:
Adrenaline causes muscle cells to lower their glycogen levels by both promoting glycogen breakdown and inhibiting its synthesis, ensuring glucose is available for energy during stress responses.
Step-by-step explanation:
In the presence of adrenaline, glycogen levels in muscle cells would be lower than in normal cells treated with adrenaline. This is because adrenaline initiates a signaling pathway that increases cyclic AMP levels. Cyclic AMP activates protein kinase A (PKA), which phosphorylates two enzymes involved in glycogen metabolism.
The first enzyme facilitates glycogen breakdown, converting it into glucose, and the second enzyme's activity, which synthesizes glycogen from glucose, is inhibited. This dual effect ensures that glucose is readily available for the muscle cell's energy needs during a "fight or flight" response, thus reducing glycogen stores.