Question

Expression of which protein is increased in mitochondria of brown adipocytes that uncouples ATP synthesis and H+ ions transfer during cold exposure?

Question 3 options:

	ATP synthase
	UCP1
	NAD transporter
	Cytochrome C

Answer 1

UCP1

Uncoupling protein (UCP1) or thermogenin are specific proteins present in the inner mitochondrial membrane of brown adipose tissue of placental mammals. This UCP1 uncouples oxidative phosphorylation in the electron transport chain, allowing the mitochondrial membrane potential to produce heat rather than synthesis of ATP. This protect the body from hypothermia during cold conditions.

When it is cold, the hypothalamus will sense cold and through sympathetic nervous system releases norepinephrine on to the brown adipose tissue, there by activating adenylate cyclase which produces cyclic AMP. This cyclic AMP, will activate protein kinase a which inturn activate triacyl glyserol lipase, that splits triglycerides into fattyacids. This huge amount of fatty acids causes the UCP1 thermogenin channel to open. This fatty acids undergo beta oxidation in mitochondrial matrix, producing NADH which continue donating electrons that help in pumping protons. Uncoupling protein is thus capable of dissipating the proton gradient generated by NADH powered pumping of protons from the mitochondrial matrix to the mitochondrial intermembrane space producing heat.