What characterizes the response of a channel-linked receptor?

• A. It is slow and prolonged.
• B. It involves the amplification of the initial signal.
• C. It is fast and brief.
• D. It requires second messengers.

Answer: (C)

Channel-linked receptors, also known as ionotropic receptors, are characterized by their rapid response to neurotransmitters or other signaling molecules. When a ligand binds to a channel-linked receptor, it causes the receptor to undergo a conformational change that opens an ion channel. This allows specific ions to flow into or out of the cell, resulting in a swift change in membrane potential.

The fast and brief nature of this response is crucial for many physiological processes, especially in the nervous system, where quick signaling is necessary for functions such as muscle contraction and synaptic transmission. This rapid response sets channel-linked receptors apart from other types of receptors, such as G-protein coupled receptors, which typically initiate slower and more prolonged responses.

In contrast to the other options, the responses associated with channel-linked receptors do not involve the extensive amplification or reliance on second messengers, which characterize other signaling pathways. Instead, the immediate effect of ion flow dictates the fast and transient nature of the signal generated by these receptors.