Question

Which of the following statements regarding metabotropic receptors is false?

1) They can be a G protein-coupled receptor.
2) They can directly open or close ion channels.
3) They can activate a G protein.
4) They usually use a second messenger.
5) They mediate membrane voltage changes via slow postsynaptic potentials.

Answer 1

The false statement about metabotropic receptors is that they can directly open or close ion channels, which is actually a characteristic of ionotropic receptors. Metabotropic receptors work through an indirect pathway involving G proteins and second messengers to modulate cellular responses.

Step-by-step explanation:

The statement that is false regarding metabotropic receptors is that they can directly open or close ion channels. Metabotropic receptors, often known as G-protein-coupled receptors (GPCRs), activate a G protein upon ligand binding. This activated G protein then interacts with other proteins in the membrane, which may be enzymes or indirectly linked ion channels, leading to a cascade of intracellular events and the generation of a second messenger such as cAMP. Second messengers can indeed cause changes in the neuron, including indirectly opening or closing ion channels, but metabotropic receptors themselves do not directly gate ion channels as the ionotropic receptors do.

Metabotropic receptors are responsible for complex and prolonged responses compared to the quick and direct responses elicited by ionotropic receptors. This is because metabotropic receptors can activate several downstream intracellular processes, including metabolic changes, alterations in gene transcription, and even modulation of membrane voltage through slow postsynaptic potentials, which are not as immediate as the changes caused by ionotropic receptors.