Receptors are specialized structures found in cell membranes. They are composed of protein molecules that bind to other specific molecules. When a receptor has bound to a molecule, it becomes active; if not, then the receptor stays inactive.
Depending on the state of the receptor (active/inactive), a change is triggered within the cell. In the most literal sense, a receptor essentially works like a lock and key. A change is triggered only when a “key” (hormones, cytokines or neurotransmitters, etc.) is used on the “lock” (receptor).
Toxins such as cyanide bind to specific receptors in the body; resulting in the inhibition of essential cellular functions. This ceases the production of ATP, and muscles such as the heart, which heavily rely on ATP quickly expend their energy and start to die. When a large number of crucial cells die, then the individual dies.
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