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Metabolism in Biochemistry Reactions

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2) The cell can transfer the high energy electrons from NADH into the mitochondria using either the glycerol phosphate shuttle or the malate-aspartate shuttle. Explain one of these two shuttles with a diagram and make sure to include details of total ATP yield. Show the structures or names of the molecules involved and also their cellular location (inside or outside the mitochondria).

3) Draw a diagram of the four complexes (complex I, II, III, IV) involved in oxidative phosphorylation, including the including details of how many protons are pumped by the transfer of two electrons through each complex, location of the mobile electron carriers involved, and the names of the enzymes that form each complex. Include details of one poison that can block electron transfer somewhere in this chain, showing the reaction blocked and a substrate that can be added to bypass the blockage. The mobile electron carriers for electron transport are NADH, FADH2, Q, cytochrome C and O2.

4) What is the effect of high AMP levels on glycolysis and gluconeogenesis? Explain the cellular rationale for this effect.

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Solution Summary

The solution contains answers and three illustrations for (1) Glycerol Phosphate Shuttle, (2) Oxidation-Reduction Reactions and (3) Allosteric (enzyme) control of gluconeogenesis and glycolysis. 1425 words.

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1) What are the roles of ubiquinone (Coenzyme Q) and cytochrome C in the electron transport chain?

Coenzyme Q10 (also known as CoQ10, Q10, vitamin Q10, ubiquinone, or ubidecarenone) is a compound that is made naturally in the body. A coenzyme is a substance needed for the proper functioning of an enzyme, a protein that speeds up the rate at which chemical reactions take place in the body. The Q and the 10 in coenzyme Q10 refer to parts of the compound's chemical structure.

Match the poison with the site it blocks in oxidative phosphorylation. Answers may be used more than once.
c, d = Dinitrophenol
f = Rotenone
a = Oligomycin
f = Bongkrekic acid
b = Carbon monoxide
e = Cyanide

2) See Figure 1. The glycerol phosphate shuttle is a secondary mechanism for the transport of electrons from cytosolic NADH to mitochondrial carriers of the oxidative phosphorylation pathway. The primary cytoplasmic NADH electron shuttle is the malate-aspartate shuttle. Two enzymes are involved in this shuttle. One is the cytosolic version of the enzyme glycerol-3-phosphate dehydrogenase (glycerol-3-PDH) which has as one substrate, NADH. The second is is the mitochondrial form of the enzyme which has as one of its' substrates, FAD+. The net result is that there is a continual conversion of the glycolytic intermediate, DHAP and glycerol-3-phosphate with the concommitant transfer of the electrons from reduced cytosolic NADH to mitochondrial oxidized FAD+. Since the electrons from mitochondrial FADH2 feed into the oxidative phosphorylation pathway at coenzyme Q (as opposed to NADH-ubiquinone oxidoreductase [complex I]) only 2 moles of ATP will be generated from glycolysis. G3PDH is glyceraldehyde-3-phoshate dehydrogenase.

3) See Fig 2.
Oxidation-Reduction Reactions
The following equations represent the oxidation-reduction reactions that are occuring in each respective complex. Everything within the reaction are those compounds or sites which are tightly bound, constitutive parts of the enzyme. Compounds outside the reaction are mobile electron (ie. hydride ion) carriers.

Abbreviations are used below: FMN - Flavin mononucleotide, Fe2+S - reduced iron-sulfur center, Fe3+S - oxidized iron-sulfur center, cyt - cytochrome, CoQ - Coenzyme Q.

Complex I

Complex II
Succinate FAD Fe2+S CoQ
Fumarate ...

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