Question

1. Write the overall reaction for pyruvate oxidation (for one pyruvate)

2. Write the overall reaction for the Citric Acid Cycle (for one acetyl-CoA)

3. What was the overall reaction for glycolysis?

4. Per glucose, how many pyruvate (and then acetyl-CoA) are formed?

5. How many Citric Acid Cycles have to take place to break down the pyruvates from one glucose molecule?

6. Write the overall reaction for pyruvate oxidation (for one glucose)

7. Write the overall reaction for the Citric Acid Cycle (for one glucose)

8. Using the protein complex abbreviations and arrows, write the path of electrons from NADH to oxygen. Circle the places in the process where hydrogen ions are pumped across the membrane.

9. Using the protein complex abbreviations and arrows, write the path of electrons from FADH2 to oxygen. Circle the places in the process where hydrogen ions are pumped across the membrane.

10. NADH molecules from glycolysis must travel into the mitochondria to pass their electrons to the electron transport chain. Because this process takes some energy, for every NADH from glycolysis, 2 ATP are formed, instead of 3. Add up all of the ATPs from each NADH and FADH2 produced during the complete breakdown of one glucose molecule. What is the net ATP gain from one glucose. Show your calculation below.

11. Oxidative phosphorylation cannot occur when there is no oxygen to accept electrons from complex 4. In anaerobic conditions( no or low oxygen), electrons quickly build up in the complexes and have nowhere to go. Interestingly, the citric acid cycle also stops when there is no oxygen.Why? What does the oxidative phosphorylation produce that citric acid cycle needs to continue working?

12. There are several known poisons that are capable of killing humans by inhibiting or stopping oxidative phosphorylation. Research two of them and describe how they affect oxidative phosphorylation below

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Answer 1

1. Pyruvate oxidation: Here pyruvate is decarboxylated and coenzyme A is added to form one molecule of acetyl CoA from a molecule of pyruvate catalyzed by Pyruvate dehydrogenase complex consisting of three enzymes (pyruvate dehydrogenase, dihydrolipoyl transacetylase and dihydrolipoyl dehydrogenase) inside the mitochondria. Overall reaction is depicted below

2. Citric acid cycle is a 8 step cyclic reaction which takes place in the mitochodrial matrix. The overall reaction is depicted below

3. Glycolysis is the initial set of reaction for targeting glucose molecules towards energy generating molecules (ATP). It is a universal pathway and  takes place in the cytosol in a 10 step reaction where a single glucose molecule is converted into two pyruvate molecules. The overall reaction is depicted below

4. Per glucose molecule two pyruvate is produced in the glycolysis process and this two pyruvate molecule is then oxidized to two acetyl CoA molecules in the mitochondria which then participates in the citric acid cycle.