The Receptors for a Group of Signaling Molecules Known as Growth

Question

The receptors for a group of signaling molecules known as growth factors are often
A) ligand-gated ion channels.
B) G protein-coupled receptors.
C) cyclic AMP.
D) receptor tyrosine kinases.
E) neurotransmitters.

Accepted Answer

Receptor tyrosine kinases are often the receptors for growth factors. This is because growth factors typically stimulate cell growth and proliferation by activating intracellular signaling pathways that involve the phosphorylation of tyrosine residues on downstream target proteins. Receptor tyrosine kinases have an intracellular kinase domain that allows them to phosphorylate tyrosine residues on themselves and on downstream target proteins, thereby activating signaling pathways that lead to changes in gene expression and cellular behavior.

Note: Option A is incorrect because ligand-gated ion channels are typically involved in neurotransmission. Option B is incorrect because G protein-coupled receptors typically activate second-messenger signaling pathways, while growth factors typically activate receptor tyrosine kinases. Option C is incorrect because cyclic AMP is a second messenger that can be activated downstream of some G protein-coupled receptors, but not typically by growth factors. Option E is incorrect because neurotransmitters are typically involved in synaptic transmission, while growth factors are involved in cell growth and proliferation.