AP BIOLOGY

Detailed explanation-1: -When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as a signal molecule.

Detailed explanation-2: -Answer and Explanation: A neurotransmitter opens a gated ion channel and the neuron responds. The neurotransmitter is the (c) signal molecule. Neurotransmitters are released from the axon terminal in a neuron and can have either an excitatory or inhibitory effect on the target tissue.

Detailed explanation-3: -Neurotransmitter-gated ion channels, also known as ionotropic receptors, are responsible for fast synaptic transmission. They decode chemical signals into electrical responses, thereby transmitting information from one neuron to another.

Detailed explanation-4: -A neurotransmitter binds to a receptor in much the same way a key fits into a lock. After transmission has occurred, the neurotransmitter is either broken down by an enzyme (a chemical that speeds up some of the body’s processes) or is reabsorbed into the neuron that released it.

Detailed explanation-5: -The neurotransmitter diffuses across the synaptic cleft and binds to ligand-gated ion channels in the postsynaptic membrane, resulting in a localized depolarization or hyperpolarization of the postsynaptic neuron.