In newborns, brown fat plays an important role in the generation of heat through which of the following actions?
A) blocking the action of hormone-sensitive lipase
B) increasing the rate of thyroxine synthesis
C) inducing of shivering by leptin
D) promoting proton leakage into mitochondria without ATP formation
E) uncoupling gluconeogenesis from triglyceride hydrolysis

Question

Quizplus · Accepted Answer

Brown fat generates heat through non-shivering thermogenesis by promoting proton leakage into mitochondria, which uncouples oxidative phosphorylation, leading to heat production without ATP formation.  The uncoupling of proton flow releases the energy of the electrochemical proton gradient as heat. This process is a normal physiological function of brown adipose tissue (BAT). Newborn babies contain BAT in their neck and upper back that serves the function of nonshivering thermogenesis. The mitochondria in BAT contain a protein called uncoupling protein 1 (UCP1; also called thermogenin). UCP1 acts as a channel in the inner mitochondrial membrane to control the permeability of the membrane to protons. When norepinephrine is released in response to cold sensation, it binds to β-adrenergic receptors on the surface of brown adipocytes triggering the activation of adenylate cyclase. Activated adenylate cyclase leads to increased production of cAMP and the concomitant activation of PKA with the result being phosphorylation and activation of hormone-sensitive lipase. The released free fatty acids bind to UCP1 triggering an uncoupling of the proton gradient and the release of the energy of the gradient as heat.

In Newborns, Brown Fat Plays an Important Role in the Generation