Question

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of substances on opposite sides of the membrane?

(A) intracellular receptor

(B) G protein-coupled receptor

(C) phosphorylated receptor tyrosine kinase dimer

(D) ligand-gated ion channel

Short answer

(A) The option “intracellular receptor” is false.

(B) The option “G protein-coupled receptor” is false.

(C) The option “phosphorylated receptor tyrosine kinase dimer” is false.

(D) The option “ligand-gated ion channel” is true.

Step-by-step solution

Receptor

Receptors are the protein molecules in the signal transduction pathway that bind with specific signaling molecules called ligands present in the cell’s outer membranes. These are activated by changing their conformation due to binding with the ligand. They have two types: intracellular and extra-cellular receptors.

Intracellular receptors include nuclear receptors and cytoplasmic receptors that generally get activated by hormones. Extra-cellular receptors includeligand-gated ion channels, toll-like receptors, and G protein-coupled receptors (GPCRs).

Explanation of option ‘(A)’

Intracellular receptors are found in the nuclear region and cytoplasm. A signal molecule passes the target cell’s plasma membrane, and binding it with these types of receptors can turn the genes on or off.

Thus,intracellular receptors lead directly to a change in gene expression but not in the distribution of substances on the opposite side of the plasma membrane.

Therefore, the given option is false.

Explanation of option ‘(B)’

A G protein-coupled receptor is the transmembrane protein found on the cell surface that works in coordination with G protein that binds to the GTP (energy-rich molecules).

Thus,G protein-coupled receptor works with G proteins to generate the signaling cascade.

Therefore, the given option is false.

Explanation of option ‘(C)’

Phosphorylated receptor tyrosine kinase dimer has enzymatic activity, catalyzing the reaction of transfer of phosphate group to the tyrosine part of another protein in signal transduction pathway.

Thus,it can phosphorylate the tyrosine amino acid of another protein to continue the signal cascade.

Therefore, the given option is false.

Explanation of option ‘(D)’

A ligand-gated ion channel is a channel receptor in the plasma membrane that allows the flow of specific ions (Na⁺ and Ca⁺) when opened or closed in response to the ligand.

Thus,binding a signaling molecule to a ligand-gated ion channel leads to directly changing the distribution of ions on opposite sides of the membrane.

Therefore, the given option is true.