Which of the following best explains how the brown adipose tissue in newborns generates large amounts of heat?
A) decreased availability of carnitine
B) increased availability of carnitine
C) increased availability of fat
D) increased formation of ATP
E) mitochondrial leak of hydrogen ions

Question

Quizplus · Accepted Answer

Brown adipose tissue generates heat through a process called non-shivering thermogenesis, which involves the mitochondrial leak of hydrogen ions. This is facilitated by the protein UCP1 (uncoupling protein 1), which allows protons to re-enter the mitochondrial matrix without generating ATP, thus releasing energy as heat.  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 hormonesensitive 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.

Which of the Following Best Explains How the Brown Adipose