What type of molecule plays a vital role in signaling between cells?

Membrane receptors are integral proteins located in the cell membrane that have specific binding sites for signaling molecules, such as hormones and neurotransmitters. When these signaling molecules bind to their corresponding receptors, they trigger a cascade of biochemical reactions within the cell, effectively transmitting information and coordinating cellular responses. This signaling mechanism is crucial for various physiological processes, including growth, immune response, and metabolism.

While enzymes, nucleic acids, and carbohydrates have important functions in cellular physiology, they do not primarily facilitate the signaling process between cells in the same direct manner as membrane receptors do. Enzymes catalyze biochemical reactions; nucleic acids are primarily involved in genetic information storage and transmission; and carbohydrates can serve as recognition molecules but do not mediate the direct signaling process that membrane receptors accomplish. Thus, membrane receptors specifically highlight the key role of signaling in intercellular communication.