Cell signalling: messages between cells — Biology, 14–17
Cells coordinate their actions by sending chemical messages and detecting them with specific receptors. The same message can produce different effects in different cells.
A message needs a receiver
A signalling molecule is like a message released by one cell. It only affects a target cell if that cell has the right receptor, a protein whose shape can bind the message. The receptor then starts changes inside the cell, such as switching genes or enzymes on.
Why cells need to talk
A multicellular body cannot work if every cell acts alone. Signals tell cells when to divide, move, release substances or change their activity, allowing a wound to close or blood glucose to be controlled. Communication turns many separate cells into a coordinated living system.
A signal in three steps
Suppose a liver cell has a receptor for adrenaline. First, an adrenal cell releases adrenaline into the blood. Second, adrenaline binds the liver receptor like a key fitting a lock. Third, the liver cell activates enzymes that release glucose, so muscles can obtain fuel quickly.
A message is not an instruction for every cell
It is tempting to think that a hormone or signal affects every cell it reaches. That seems reasonable because the molecule travels through the whole body, but only cells with the matching receptor can detect it. Even then, their internal machinery decides the final response.
Medicine reads these messages
Many medicines work by copying, blocking or changing cell signals. An asthma drug can activate receptors that relax airway muscles, while another drug can block a receptor used by a virus or cancer cell. Understanding the message pathway helps predict both benefits and side effects.
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