Question

Diagram and describe how uncoupling proteins work, including their effects on cellular respiration. Explain how these proteins might play a role in thermogenesis and the control of reactive oxygen species such as superoxide. (Hint: you’ll need to explain the ETC and proton gradient for this.)

(no bullet points, essay format)

Answer 1

An uncoupling protein (UCPs) is found in inner membrane of mitochondria which is essentially a proton channel or transporter. Therefore, it capable of dispersing the proton gradient that is generated by NADH-powered pumping of protons from the mitochondrial matrix to the mitochondrial intermembrane space.

UCPs decrease the proton gradient generated in oxidative phosphorylation. They do this by enhancing the permeability of the inner mitochondrial membrane and this ultimately allow the protons to be pumped into the intermembrane space to return to the mitochondrial matrix. It activates heat generation in fat which uncouples the respiratory chain and permitted the fast substrate oxidation with a low rate of ATP production. These proteins are also related to other mitochondrial metabolite transporters like the adenine nucleotide which is involved in translocation of protons from the mitochondrial intermembrane space to the mitochondrial matrix. Some of these proteins restricted to brown adipose tissues, where they provide a mechanism for the huge heat-generating capacity of the tissue.

These proteins may play a role in thermogenesis and the control of reactive oxygen species (ROS) like superoxide because they retain the ability to uncouple the proton created by NADH-powered pumping of protons from the mitochondrial matrix to the mitochondrial intermembrane space.

Mainly, UCPs are involved in the defense against reactive oxygen species (ROS) and in this way prevent the oxidative damage. A high mitochondrial membrane potential activates an increase in ROS production as it is clear that UCPs are uncoupling protein and therefore the presence of UCPs could protect against ROS production. It is also witnessed that UCP activity is regulated by superoxide or ROS products.