What function do G Protein Coupled Receptors primarily have?

G Protein Coupled Receptors (GPCRs) primarily function by activating G-proteins, which are intracellular proteins that play a crucial role in transmitting signals from outside the cell to the inside. When a ligand, such as a hormone or neurotransmitter, binds to a GPCR, it causes a conformational change in the receptor. This change allows the GPCR to interact with and activate G-proteins, which then dissociate into their active forms. These activated G-proteins can then interact with various effector molecules in the cell, leading to a variety of downstream cellular responses.

This mechanism is fundamental to many physiological processes, including sensory perception, immune responses, and the regulation of mood. Given the diverse roles of GPCRs, they are a key target for pharmaceuticals, as modulating their activity can have significant effects on health and disease.

In contrast to this primary role, the other options describe functions that GPCRs do not directly perform. For instance, while changes in ion flow can occur as a result of GPCR activation (especially through downstream signaling pathways), GPCRs themselves do not directly alter ion flow across membranes. Similarly, while they might be involved in metabolic processes such as glucose uptake, they do not directly