In unstimulated cells, the state of G alpha (orange circles) is defined by its interaction with GDP, G beta-gamma (purple circles), and a G-protein-coupled receptor (GPCR; light green loops).

After exchange of GDP with GTP on the alpha subunit, both the alpha subunit and the beta-gamma complex may interact with other molecules to promote signaling cascades. Note that both the alpha ...

These nicotinic receptors are composed of five subunits -- two alphas and one beta, gamma, and epsilon; one acetylcholine molecule binds to a single alpha subunit. These nicotinic receptors are ...

The thicker the substance, the more the radiation is absorbed. Alpha, beta and gamma radiations penetrate materials in different ways. Alpha radiation is the least penetrating. It can be stopped ...