The figure shows two signaling molecules binding to a transmembrane receptor protein (shown at I). What do these signaling molecules do?
Correct Answer: They activate the receptor proteins, causing them to initiate a signal transduction pathway.
C. Signaling molecules are small molecules that bind to larger receptor proteins embedded in the plasma membrane. In general, the binding of the signaling molecule to the receptor protein induces a change in the shape of the receptor protein. Although you do not need to know this to answer this question, the receptor protein here is a receptor tyrosine kinase (RTK) that, when activated by the signaling molecule, causes two RTKs to form a pair (dimer). Autophosphorylation follows, allowing the subsequent phosphorylation of relay proteins.
