Question

What kind of transporter is the acetylcholine receptor of skeletal muscle membrane, and how is it controlled?

Short answer

Answer: The acetylcholine receptor of the skeletal muscle membrane is a ligand-gated ion channel or ionotropic receptor. It is controlled by the binding of the neurotransmitter acetylcholine, which triggers the opening of the ion channel and initiates muscle contraction. Acetylcholinesterase hydrolyzes acetylcholine in the synaptic cleft, terminating its action and allowing the muscle cell to relax.

Step-by-step solution

1. Identifying the transporter type

The acetylcholine receptor of the skeletal muscle membrane is a ligand-gated ion channel, also known as an ionotropic receptor. This type of receptor is a transmembrane protein that forms a channel through which ions can pass when the receptor is activated by a specific ligand, in this case, acetylcholine.

2. Describing its control mechanism

The acetylcholine receptor is controlled by the binding of the neurotransmitter acetylcholine. When acetylcholine is released from a motor neuron, it crosses the synaptic cleft and binds to the acetylcholine receptor on the postsynaptic membrane of the skeletal muscle cell. Binding of acetylcholine to the receptor causes a conformational change, opening the ion channel and allowing the influx of sodium ions (Na+) and the efflux of potassium ions (K+). This causes a depolarization of the muscle cell membrane and initiates the events leading to muscle contraction. Once the acetylcholine molecules unbind from the receptor, the ion channel closes, and the muscle cell membrane returns to its resting state. Acetylcholinesterase, an enzyme present in the synaptic cleft, hydrolyzes acetylcholine into choline and acetate, which terminates the action of acetylcholine and allows the muscle cell to relax.