Both DNP (2,4-dinitrophenol) and thermogenin uncouple mitochondrial electron tra

Question

Both DNP (2,4-dinitrophenol) and thermogenin uncouple mitochondrial electron transport from ATP synthesis. Oxygen consumption and the oxidation of NADH both increase, but no ATP is synthesized. Thermogenin is expressed in the mitochondria of brown fat cells in newborn animals and adult mammals that hibernate. DNP was marketed in the 1930s as a diet pill, but in addition to causing weight loss it sometimes caused death.

a. Compare/contrast the mechanisms by which these uncouplers affect ATP synthesis. (4pts)

b. Why is the presence of thermogenin beneficial to babies and hibernating animals, whereas taking DNP as a diet pill has a high chance of killing you? (3pts)

Explanation / Answer

Ans part auncoupling agents disrupt the ability to aintain an intact gradient by making the mitochondrial membrane porous. As a result , uncoupling is reversible and cannot be bypassed. thermogenin allows for fast substrate oxidationwith low ATP generation with high heat release, particularly useful for infants or mammals that hibernate. This occurs exclusively in in brown fat and is inhibited by ADP and GDP. On the other hand , DNP has no regulatory mechanism within cells , so it would occur in all cells rather than just a selective ones.

b.Thermogenin is a inner membrane mitochondrial protein exclusive to brown adipocytes that functions as a proton transporter.It allows dissipation as heat of the proton gradient generated by respiratory chain and thereby oxidative phosphorylation. However DNP was marketted in the 1930's as a diet pill. DNP treatment not only resulted in weight loss but also death of patient

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