Non-shivering thermogenesis contributes significantly to heat production in newborns exposed to cold. Which intracellular protein mediates this form of thermogenesis?

• A Cytochrome oxidase in liver mitochondria
• B Sarcoplasmic reticulum calcium ATPase in skeletal muscle
• C Na+/K+ ATPase in white adipose tissue
• D Uncoupling protein 1 (thermogenin) in brown adipose tissue mitochondria ✓

Explanation

Brown adipose tissue expresses uncoupling protein 1 (UCP1, thermogenin) in the inner mitochondrial membrane. Sympathetic release of norepinephrine acting on beta-3 receptors activates lipolysis, and UCP1 dissipates the proton gradient as heat instead of ATP. Skeletal muscle calcium cycling and hepatic cytochrome oxidase do not mediate regulated heat production, and white adipose tissue lacks significant UCP1 expression.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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