Bke2 Biochemistry 1998 Exercises

Group exercise: Proteins in the CAC and in oxidative phosphorylation

Glycolysis produces pyruvate from the partial oxidation of glucose. What is the fate of pyruvate under a) anaerobic, and b) aerobic conditions? Where in the cell does the further metabolism of pyruvate take place?
One high-energy phosphate bond (in the form of GTP) is generated in one pass through the citric acid cycle. Where does the energy invested in making this GTP come from?
In one of the oxidation-reduction reactions of the citric acid cycle, FAD rather than NAD⁺ is used as the electron acceptor. Which step? Why?
In the first step of the citric acid cycle, the enzyme citrate synthase catalyzes the condensation of oxaloacetate and acetyl-CoA. Does it matter in which order the substrates bind? Why?
Explain the terms chiral, prochiral, stereospecificity. Give an example of a stereospecific reaction.
Isocitrate is an intermediate in the citric acid cycle. In plants (and some bacteria) isocitrate can also be used in a different sequence of reactions forming an alternative metabolic pathway. What is the purpose of this pathway? What controls which pathway will be used?
Where does oxidative phosphorylation take place?
The redox potential is a key concept for the understanding of what drives electron transport in biological membranes. Why?.
What is the net reaction of mitochondrial electron transfer?
Describe schematically, how the energy (in the form of high-potential electrons) generated in glycolysis and the citric acid cycle is used to make ATP.

Reading material: Horton, Chapters 13 and 15 (or Stryer, Chapters 20, 21).

Lectures:
The citric acid cycle and oxidative phosphorylation
Glucose metabolism
Oxidative phosphorylation

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