When the Ca2+ levels drop:

Myosin LC is dephosphorylated by MLC phosphatase, causing muscle relaxation.

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#Unit 6. System Physiology – Plant

cytochrome C oxidoreductase, couples the transfer of electrons from ubiquinol (QH2) to cytochrome c with the vectorial transport of protons from the matrix to the intermembrane space.

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#Id: 3278

#Unit 6. System Physiology – Plant

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#Id: 3287

#Unit 6. System Physiology – Plant

the Q cycle, has been proposed for the passage of electrons and protons through the complex. The net equation for the redox reactions of the Q cycle is

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#Id: 3288

#Unit 6. System Physiology – Plant

Complex IV, also called cytochrome oxidase, carries electrons from cytochrome c to molecular oxygen, For every four electrons passing through this complex, the enzyme consumes four “substrate” Hfrom the matrix (N side) in converting O2 to 2H2O

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#Unit 6. System Physiology – Plant

The overall reaction catalyzed by Complex IV is

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#Id: 3294

#Unit 6. System Physiology – Plant

Ubiquinone (Q) is reduced by four ways;

a. By the oxidation of NADH in complex I
b. Electrons from succinate pass through a flavoprotein with the cofactor FAD and several Fe-S
centers (in Complex II) on the way to Q
c. Glycerol 3-phosphate donates electrons to a flavoprotein (glycerol 3-phosphate dehydrogenase)
on the outer face of the inner mitochondrial membrane, from which they pass to Q.
d. Acyl-CoA dehydrogenase (the first enzyme of oxidation) transfers electrons to electron-
transferring flavoprotein (ETF), from which they pass to Q via ETF