Q1. Complete the Chart: Complete Oxidation of 1 Molecule of Glucose to CO2 and H2O in the Prokaryotic Cell

Background

Topic: Microbial Metabolism – Cellular Respiration

This question tests your understanding of the steps and energy yield involved in the complete aerobic oxidation of glucose in prokaryotic cells. It covers glycolysis, the intermediate (prep) step, the Krebs cycle, and the electron transport chain, as well as the mechanisms of ATP production (substrate-level and oxidative phosphorylation).

Key Terms and Formulas

• Substrate-level phosphorylation: ATP synthesis by direct transfer of a phosphate group to ADP from a phosphorylated intermediate.

• Oxidative phosphorylation: ATP synthesis using energy derived from the transfer of electrons through the electron transport chain to oxygen.

• Glycolysis: The breakdown of glucose to pyruvic acid, producing ATP and NADH.

• Intermediate (prep) step: Conversion of pyruvic acid to acetyl-CoA, producing NADH and CO2.

• Krebs cycle: Series of reactions that oxidize acetyl-CoA to CO2, generating NADH, FADH2, and ATP.

• Electron Transport Chain (ETC): Series of proteins that transfer electrons from NADH and FADH2 to oxygen, producing ATP.

• ATP Yield: In prokaryotes, the theoretical maximum ATP yield from one glucose is typically 38 ATP.

• Key Equations:

Step-by-Step Guidance

1. Start by identifying the main stages of glucose oxidation: Glycolysis, the intermediate (prep) step, Krebs cycle, and the electron transport chain.

2. For each stage, determine which energy carriers (ATP, NADH, FADH2) are produced and by which mechanism (substrate-level or oxidative phosphorylation).

3. Use the provided definitions to match each process:

   • For glycolysis, look for the definition describing the conversion of glucose to pyruvic acid.

   • For the intermediate step, find the definition about converting pyruvic acid to acetyl-CoA.

   • For the Krebs cycle, identify the definition involving the addition of acetyl-CoA to oxaloacetic acid.

   • For the electron transport chain, select the definition about electrons passing to oxygen through cytochromes.

4. Calculate the ATP, NADH, and FADH2 produced at each stage. Remember:

   • Glycolysis produces a net gain of ATP and NADH.

   • The intermediate step produces NADH per pyruvate (multiply by 2 for one glucose).

   • The Krebs cycle produces ATP, NADH, and FADH2 per acetyl-CoA (again, multiply by 2).

5. For oxidative phosphorylation, multiply the total NADH by 3 and FADH2 by 2 to find the ATP produced via the ETC.

6. Add up the ATP from substrate-level phosphorylation and oxidative phosphorylation to get the total ATP yield for one glucose molecule in a prokaryotic cell.

7. Stop here and try to fill in the chart and calculate the totals using the steps above. Make sure to use the correct definitions for each process and double-check your ATP calculations!

Try solving on your own before revealing the answer!