Why is Judy so happy today? A) She's my friend. B) She had lunch. C) She passed the entrance exam. D) She is a pretty girl.
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【多选题】Explain how some intracellular signaling proteins act as molecular switches.
A.
Many intracellular signaling proteins behave as molecular switches: receipt of a signal causes them to toggle from an inactive to an active state.
B.
Once activated, these proteins can stimulate—or in some cases suppress—other proteins in the signaling pathway. They then persist in an active state until some other process switches them off again.
C.
If a signaling pathway is to recover after transmitting a signal and make itself ready to transmit another, every activated protein in the pathway must be reset to its original, unstimulated state.
D.
Thus, for every activation step along the pathway, there exists an inactivation mechanism. The two are equally important for a signaling pathway to be useful.