The oxidation of glucose (C₆H₁₂O₆) in body tissue produces CO₂ and H₂O. In contrast, anaerobic decomposition, which occurs during fermentation, produces ethanol (C₂H₅OH) and CO2.
(b) Compare the maximum work that can be obtained from these processes under standard conditions.
C₆H₁₂O₆(s) + 6 O₂(g) ⇌ 6 CO₂(g) + 6 H₂O(l)
C₆H₁₂O₆(s) ⇌ 2 C₂H₅OH(l) + 2 CO₂(g)

Verified step by step guidance

1. 1. The maximum work that can be obtained from a process is related to the change in Gibbs free energy (ΔG) for the process. The Gibbs free energy is a thermodynamic potential that measures the maximum reversible work that a system can perform at constant temperature and pressure. The formula for Gibbs free energy is ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy.
2. 2. For the oxidation of glucose, the reaction is C₆H₁₂O₆(s) + 6 O₂(g) ⇌ 6 CO₂(g) + 6 H₂O(l). You would need to look up the standard enthalpies of formation (ΔH_f) and standard entropies (S₀) for each substance involved in the reaction. Then, calculate the ΔH and ΔS for the reaction using the formulas ΔH = ΣΔH_f(products) - ΣΔH_f(reactants) and ΔS = ΣS₀(products) - ΣS₀(reactants).
3. 3. For the anaerobic decomposition of glucose, the reaction is C₆H₁₂O₆(s) ⇌ 2 C₂H₅OH(l) + 2 CO₂(g). Similarly, look up the standard enthalpies of formation and standard entropies for each substance involved in the reaction. Then, calculate the ΔH and ΔS for the reaction using the same formulas as in step 2.
4. 4. Once you have the ΔH and ΔS for both reactions, you can calculate the ΔG for each reaction using the formula ΔG = ΔH - TΔS. Remember to convert the temperature to Kelvin if it is given in degrees Celsius.
5. 5. Compare the ΔG values for the two reactions. The reaction with the more negative ΔG value can perform more work under standard conditions. This is because a negative ΔG indicates that the reaction is spontaneous, and the magnitude of ΔG indicates the maximum work that can be obtained from the process.

Key Concepts

Oxidation and Reduction Reactions

Oxidation and reduction reactions, collectively known as redox reactions, involve the transfer of electrons between substances. In the context of glucose metabolism, glucose is oxidized to produce carbon dioxide and water, releasing energy. Understanding these reactions is crucial for comparing the energy yield of aerobic versus anaerobic processes.

Standard Gibbs Free Energy Change (ΔG°)

The standard Gibbs free energy change (ΔG°) is a thermodynamic quantity that indicates the maximum reversible work obtainable from a process at standard conditions. It helps determine the spontaneity of a reaction; a negative ΔG° indicates that the reaction can occur spontaneously. This concept is essential for comparing the energy efficiency of glucose oxidation and fermentation.

Cellular Respiration vs. Fermentation

Cellular respiration is an aerobic process that fully oxidizes glucose to carbon dioxide and water, yielding a high amount of ATP, while fermentation is an anaerobic process that partially breaks down glucose to produce ethanol and carbon dioxide, resulting in less ATP. Understanding the differences in energy production between these two pathways is key to evaluating their maximum work output.