Brown adipose tissue obtained from the interscapular region of a newborn shows multilocular adipocytes with abundant mitochondria. Which protein in these mitochondria accounts for its role in non-shivering thermogenesis?

• A Hormone-sensitive lipase in the lipid droplet
• B Cytochrome oxidase in the outer mitochondrial membrane
• C Lipoprotein lipase on the capillary endothelium
• D Uncoupling protein 1 (thermogenin) in the inner mitochondrial membrane ✓

Explanation

Thermogenin, or uncoupling protein 1, sits in the inner mitochondrial membrane of brown adipocytes and forms a proton leak that dissipates the proton gradient as heat instead of generating ATP. This allows rapid heat production in newborns exposed to cold, under sympathetic noradrenaline stimulation. Lipoprotein lipase and hormone-sensitive lipase mobilize lipid substrate but do not generate heat directly, and cytochrome oxidase is not located on the outer membrane.

Reference: Ross and Pawlina Histology: A Text and Atlas, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.