The reactants are like a key that fits into the enzyme forming the lock
When cells communicate by the signaling process, one cell produces a signaling molecule that must be received by the signal receptor on or in the responding cell. Signaling molecules are often called ligands, a general term for molecules that bind specifically to other molecules (such as receptors).
Answer:
Ion- an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
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Brainliest?