Question

How are monomeric and trimeric G-proteins different?

A) Monomeric G-proteins have three subunits, while trimeric G-proteins have one subunit.
B) Monomeric G-proteins are involved in intracellular signaling, while trimeric G-proteins are membrane-bound.
C) Monomeric G-proteins bind to GTP, while trimeric G-proteins bind to GDP.
D) Monomeric G-proteins are only found in eukaryotes, while trimeric G-proteins are found in prokaryotes.

Answer 1

Trimeric G-proteins, composed of α, β, and γ subunits, are activated by G-protein-coupled receptors and involved in producing second messengers like cAMP. Monomeric G-proteins are single-subunit GTPases involved in various intracellular signaling processes.

Step-by-step explanation:

Monomeric and trimeric G-proteins are distinct in their composition and function in cell signaling pathways. Trimeric G-proteins, also known as heterotrimeric G-proteins, are composed of three subunits: alpha (α), beta (β), and gamma (γ).

When a signaling molecule binds to a G-protein-coupled receptor in the plasma membrane, GDP associated with the α subunit is exchanged for GTP. This causes the β and γ subunits to dissociate from α, and a cellular response is triggered by either the α subunit or the dissociated βγ pair.

In contrast, monomeric G-proteins, often referred to as small GTPases, consist of a single subunit that can bind GTP or GDP and are involved in a variety of intracellular signaling processes.

Trimeric G-proteins are integral to signal transduction pathways that involve receptors capable of binding hormones or other signaling molecules, leading to the activation of enzymes such as adenylate cyclase and the production of second messengers like cAMP.

On the other hand, monomeric G-proteins typically interact with downstream effectors that are part of different signaling cascades within the cell.