High resolution

Module 7: Figure brown fat cell

Brown fat cell thermogenesis.

Sympathetic nerves release noradrenaline that acts through the cyclic AMP (cAMP) signalling pathway to control heat production by brown fat cells. Cyclic AMP acts through cyclic-AMP-dependent protein kinase A (PKA) to phosphorylate and stimulate hormone-sensitive lipase (HSL) to release free fatty acids (FFA) that are then metabolized by the tricarboxylic acid (TCA) cycle in the mitochondria. FFA also provides the stimulus to activate uncoupling protein 1 (UCP1) that dissipates the H+ gradient resulting in the production of heat that is carried away by the blood vessels.