Lecture 9: Uncouplers of oxidative phosphorylation Flashcards Preview

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Flashcards in Lecture 9: Uncouplers of oxidative phosphorylation Deck (9)
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1

What are uncouplers?

Uncouplers are transporting ionophores, lipid-soluble weak acids. Their presence on the inner mitochondria membrane increases the membrane's permeability to protons and provides a route for the dissipation of the electrochemical proton gradient. that doesn't require ATP synthesis.

2

Give an example of an uncoupler.

2,4-dinitrophenol. It was prescribed as a slimming agent and caused weight loss then death.

3

What is another name for the uncoupling protein?

Thermogenin

4

Which tissue is thermogenin produced in?

Brown adipose tissue of newborn or hibernating mammals.

5

Why is brown adipose tissue brown?

Due to the huge number of mitochondria, which are brown because they contain cytochrome b.

6

What is the function of thermogenin?

It blocks the development of a proton electrochemical gradient, thereby stimulating respiration. Delta G (free energy) of respiration is dissipated as heat.

It is important that this heat is released, because newborn mammals can't shiver (it takes 2-3 years for all muscles to be able to shiver), so depend on this mechanism, which is called 'non-shivering thermogenesis'.

Although this is costly respiration-wise, providing heat for the organism is very important.

7

What is thermogenin allosterically activated and inhibited by?

Activated by free fatty acids.
Inhibited by purine nucleotides

8

What controls the levels of free fatty acids in adipose tissue?

A hormone called noradrenaline.

9

Describe how thermogenesis is under hormonal control.

1) Noradrenaline binds to a receptor
2) This stimulates adenylate cyclase and levels of cAMP go up
3) cAMP activates cAMP-dependent kinase
4) This kinase phosphorylates triacylglycerol lipase, thus activating it
5) Activated triacylglycerol lipase then hydrolyses triacylglycerols to free fatty acids which activate/open the thermogenin channel.