Chapter 13 (right now only 13.1 and 13.3) Flashcards Preview

Biochemistry 431 > Chapter 13 (right now only 13.1 and 13.3) > Flashcards

Flashcards in Chapter 13 (right now only 13.1 and 13.3) Deck (18):
1

Q # 36 Why is the cell's ability to regenerate NAD+ critical to glycolysis? Which glycolytic enzyme requires NAD+?

The ability to regenerate NAD+ is important for two reasons 1) the Oxidation of NAD+ is critical for the generation of energy 2) NAD+ needs to be regenerated to be used in glycolysis. The glycolytic enzyme that requires NAD+ is glyceraldehyde 3-Pdehydrogenase

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Q # 37 What is the most important consequence to the cell of the reduction of pyrvate to lactate by lactate dehydrogenase?

NAD+ is regenerated by reduction of pyruvate to lactate, which allows for the continuation of glycolysis.

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Q # 38 What is the net yield of ATP per glucose by this pathway? (Lactic acid fermentation)

2 ATP

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In fermentation, how is NAD+ regenerated without oxygen as an electron acceptor?

Pyruvate is reduced to lactate by lactate dehydrogenase; no net change in NAD

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Q #40 Do all organisms perform alcohol fermentation and lactic acid fermentation?

NO

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Q # 41 What is the net yield of ATP per glucose molecule by this pathway?

2 ATP

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Pyruvate decarboxylase

pyruvate is decarboxylated (Mg2+ and TPP reagents)

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alcohol dehydrogenase

acetylaldehyde is reduced by NADH to ethanol

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Q # 2 What is accomplished in the preparatory phase of glycolysis? What is accomplished in the payoff phase of glycolysis?

1) In the preparatory phase of glycolysis, 2 ATP invested, which raises the free energy of the intermediates, G3P is produced x 2 (glucose primed) 2) 4 ATP produced by substrate level phosphorylation

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Q # 3 How is the phosphorylation of G3P in the payoff phase of glycolysis different from the phosphorylation of glucose in the preparatory phase?

phosphate added to G3P occurs from free cytosolic phosphate pi not ATP.

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Q # 4 Describe three catabolic fates of pyruvate?

ETC chain, lactic acid fermentation, ethanol fermentation

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Q # 7 How can the biologically available energy remaining in pyruvate be extracted?

By CAC or oxidative phosphorylation

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Q # 8 What are the three functions of phosphoryl groups of phosphorylated intermediates?

1) Force glucose to stay in the cell 2) Conserve energy from ATP, provide energy to phosphorylate ADP during (1,3-bisphosphoglycerate and phosphoenolpyruvate) 3) Binding energy of phosphate groups help lower the activation energy of enzymatic reactions

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Q # 11 What is the general role of a kinase?

The transfer of phosphate groups

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Q # 14 Why is isomerization critical to subsequent steps?

Because phosphate cannot be added to carbonyls, isomerization is need to put the carbonyl on C2.

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Q # 15 Why is PFK-1 a good candidate for a regulatory enzyme?

PFK-1 is the first committed step in glycolysis.

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Q # 16 What conditions activate PFK-1? What conditions inactivate PFK-1?

Activated in low ATP/high ADP conditions; inhibited by high levels of ATP and fatty acids

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Q # 17 If PFK-1 is inhibited, in which direction will the reaction catalyzed by phosphohexose isomerase proceed?

Opposite direction

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