When both are in their receptor sites, the molecules form a dimer (two molecules joined together). atp is converted to adp and the attached to the tyrosine molecules. the addition of the a cascade of cellular responses

When both _signal molecules_ are in their receptor sites, the molecules form a dimer (two molecules joined together). ATP is converted to ADP and the _phosphate group_ gets attached to the tyrosine molecules. The addition of the _ relay proteins_ causes a cascade of cellular responses.

Explanation:

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