Answer:
d. Ligand-gated ion channels
Explanation:
<em>a.Intracellular receptor</em>: it's activated through second messengers s<em>ince its activation and actions happen only inside the cell there's no distribution of ions on opposite sides of the membrane.</em>
<em>b.G-protein-coupled receptor:</em> these receptors bind specific ligands at the cell surface (hormones and neurotransmitters) to relay the signal across the membrane. <em>This means they act as a messager, there's no distribution of ions.</em>
<em>c.Phosphorylated receptor tyrosine kinase dimer</em>: works as a messenger as well, <em>it propagates a signal through the plasma membrane </em>when it allows tyrosine to be trans phosphorylated.
d. Ligand-gated ion channels open to allow ions such as Na+, K+, Ca2+ or Cl- in response to the binding of a chemical messenger, one example of this kind of channel in action is when a neurotransmitter binds to a receptor located on the postsynaptic neuron, <em>opening ion channels, this lead to a flow of ions across the cell membrane that turns into a depolarization or a hyperpolarization by changing the distribution of ions on opposite sides of the membrane.</em>
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