Identify whether the statement is true or false, and why. "each type of receptor protein is specific to a certain signal or type of signal." a. true b. false, it should read "receptor proteins can receive signals from many types of signal molecules." c. false, it should read "receptor proteins are only used in synapses to receive neurotransmitters." d. false, it should read "receptor proteins are universal and can receive signals from any type of signal molecules."

A. True

Explanation: Cell receptors are proteins that receive  signals and trigger a signal cascade for the cell can respond. There's many types of  receptors, depend of their location and their enzymatic activity, and each type can recognize  certain  signals. For example, tyrosine-kinase receptors can recognize growth factors, JAK associated receptors can recognize cytokines, etc. That specificity is given by the structure of the receptor and the structure of the signal.