Question

You shiver when you are cold because the ATP hydrolysis that occurs during this (or any other muscle contraction) produces heat. Newborn mammals lacking fur or hibernating mammals contain brown adipose tissue that generates heat via non shivering thermogenesis. Central to this mechanism is a mitochondrial protein called Thermogenin, which acts as a proton channel but does not synthesize ATP. How does this work? Can you think of another mechanism whereby heat could be generated without shivering?

Answer 1

Thermogenin is an uncoupler found in the mitochondria, the energy-generating organelle of a cell, of BAT. Mitochondria use fats and glucose to produce ATP in a process that involves storing energy in the form of a proton gradient across the inner mitochondrial membrane. This energy is typically used to synthesize ATP when protons flow across the membrane. However, in BAT, thermogenin allows for the protons to run down its gradient in an alternative route without producing ATP, allowing for the energy stored in the proton gradient to be dissipated as heat.

The blood flow decreases; blood vessels contract and retain the heat in that area.