Cell Signaling Practice Test 2026 - Free Cell Signaling Practice Questions and Study Guide

The primary function of a G protein in cellular signaling is to relay signals from receptors to intracellular targets. When a ligand binds to a G protein-coupled receptor (GPCR) on the cell surface, it causes a conformational change in the receptor, activating the associated G protein. The G protein, composed of three subunits (alpha, beta, and gamma), then dissociates and interacts with various downstream effectors within the cell, such as enzymes or ion channels. This interaction leads to a cascade of intracellular events, influencing numerous cellular processes, such as metabolism, growth, and gene expression. This signaling capability makes G proteins pivotal in transmitting extracellular signals into appropriate cellular responses.

Other options are related to the signaling process but do not define the primary purpose of G proteins. For instance, while ligands bind to receptors, G proteins do not perform this function. Similarly, G proteins are not second messengers themselves; rather, they facilitate the activation of pathways that may lead to the production of second messengers. Lastly, G proteins do not serve as transcription factors; instead, they relay information that could ultimately affect transcription factors at downstream targets. Thus, the role of G proteins as relays in the signaling cascade is fundamental to understanding cell