Epinephrine Increases Available Glucose by Binding to a Cell Surface

Multiple Choice

Epinephrine increases available glucose by binding to a cell surface receptor that activates a G protein, which then activates cAMP-dependent protein kinase, then phosphorylase kinase, and finally glycogen phosphorylase, which breaks down glycogen into glucose-1-phosphate. Epinephrine breaks down glucose by activating five different proteins, stimulating glycogen synthase. Experimentally, you discover that in addition to stimulating the G protein, the epinephrine receptor can also directly stimulate glycogen synthase, bypassing the intermediate proteins. This would be an example of

A) a network.
B) a feedforward relay.
C) crosstalk.
D) positive feedback.