Question

In biological cells that have a plentiful supply of \(\mathrm{O}_{2}\), glucose is oxidized completely to \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\) by a process called aerobic oxidation. Muscle cells may be deprived of \(\mathrm{O}_{2}\) during vigorous exercise and, in that case, one molecule of glucose is converted to two molecules of lactic acid, \(\mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{COOH}\), by a process called anaerobic glycolysis. \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{~s})+6 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 6 \mathrm{CO}_{2}(\mathrm{~g})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{I})\) \(\Delta H^{\circ}=-2880 \mathrm{~kJ} / \mathrm{mol}\) \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{~s}) \rightarrow 2 \mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{COOH}(\mathrm{s}) ;\) \(\Delta H^{\circ}=+2530 \mathrm{~kJ} / \mathrm{mol}\) Which of the following statements is true regarding aerobic oxidation and anaerobic glycolysis with respect to energy change as heat? (a) Aerobic oxidation has biological advantage over anaerobic glycolysis by \(5410 \mathrm{~kJ} / \mathrm{mol}\). (b) Aerobic oxidation has biological advantage over anaerobic glycolysis by \(350 \mathrm{~kJ} / \mathrm{mol}\) (c) Anaerobic glycolysis has biological advantage over aerobic oxidation by \(5410 \mathrm{~kJ} / \mathrm{mol}\). (d) Anaerobic glycolysis has biological advantage over aerobic oxidation by \(350 \mathrm{~kJ} / \mathrm{mol}\).

Short answer

Aerobic oxidation has a biological advantage over anaerobic glycolysis by 5410 kJ/mol.

Step-by-step solution

Understand the Energy Change in Aerobic Oxidation

Assess the given energy change for aerobic oxidation of glucose. The energy change is provided as \(\Delta H^\circ = -2880 \text{ kJ/mol} \), which implies that 2880 kJ/mol of energy is released during the process.

Understand the Energy Change in Anaerobic Glycolysis

Observe the energy change for anaerobic glycolysis of glucose. The corresponding energy change is \(\Delta H^\circ = +2530 \text{ kJ/mol} \), indicating that 2530 kJ/mol of energy is consumed.

Calculate the Biological Advantage

Determine the biological advantage of aerobic oxidation over anaerobic glycolysis by subtracting the energy consumed in anaerobic glycolysis from the energy released in aerobic oxidation: \(2880 \text{ kJ/mol} - (-2530 \text{ kJ/mol}) = 5410 \text{ kJ/mol}\).

Choose the Correct Statement

Based on the calculation in Step 3, aerobic oxidation has a biological advantage over anaerobic glycolysis because it provides more energy, which is by 5410 kJ/mol. The correct choice is the statement that reflects this advantage.

Key concepts

Energy Change in Metabolism

The process of metabolism encompasses the entire set of life-sustaining chemical reactions in organisms, and central to these reactions is the conversion of energy. Energy change in metabolism is vital because it drives physical and biological functions, from movement to cellular repair. Aerobic oxidation and anaerobic glycolysis are two metabolic pathways that break down glucose, but with different energy changes.

During aerobic oxidation, cells use oxygen to completely convert glucose to carbon dioxide and water, releasing a significant amount of energy as reflected by the negative enthalpy change \( \Delta H^\circ = -2880 \text{ kJ/mol} \) - the 'minus' sign indicating that energy is released to the surroundings. In contrast, anaerobic glycolysis, which proceeds without oxygen, converts one molecule of glucose into two molecules of lactic acid along with a positive enthalpy change \( \Delta H^\circ = +2530 \text{ kJ/mol} \) - the 'plus' sign here signifies that energy is absorbed from the surroundings. The difference in these values highlights the efficiency of these pathways and their roles under different physiological conditions like rest or rigorous exercise.

Biochemical Energy

Biochemical energy refers to the form of energy that is harnessed from chemical bonds in molecules within biological systems. It's fundamental for various cellular processes including muscle contraction, cell division, and the synthesis of biomolecules. This energy primarily originates from nutrients like carbohydrates, fats, and proteins.

In the context of glucose metabolism, the biochemical energy is derived from the breaking of molecular bonds within glucose molecules. The more efficient process of aerobic oxidation maximizes the amount of energy obtained from glucose, as compared to anaerobic glycolysis. An understanding of biochemical energy is critical for analyzing metabolic diseases, crafting diets, and even developing new ways to optimize physical performance and health.

Enthalpy Change

Enthalpy change \( \Delta H \) is a thermodynamic concept that quantifies the heat absorbed or released in a reaction, at constant pressure. This is a core concept in thermodynamics and chemistry, and in biological terms, it signifies the amount of energy in the form of heat that a metabolic reaction contributes to or takes from the organism's environment.

In aerobic oxidation, the large negative enthalpy change \( \Delta H^\circ = -2880 \text{ kJ/mol} \) indicates that energy is released as heat, which can potentially be used for other biological activities. Conversely, anaerobic glycolysis's positive enthalpy change means that it requires an input of energy, making it less effective from an energy production standpoint. The enthalpy change concept helps explain why certain metabolic pathways are favored under specific conditions and how organisms adapt their energy usage.

Glucose Metabolism

Glucose metabolism is crucial for providing energy to nearly all life forms. It involves a series of enzymatic reactions that breakdown glucose to release energy for cellular functions. There are two main pathways for glucose breakdown: aerobic oxidation and anaerobic glycolysis.

Aerobic oxidation, requiring oxygen, involves a complete breakdown of glucose into water and carbon dioxide and is highly energy-efficient, while anaerobic glycolysis, which occurs without oxygen, results in the partial breakdown of glucose to lactic acid. The latter is less efficient, producing less energy per molecule of glucose. Understanding glucose metabolism is critical, as it forms the basis of energy production in cells and is a critical element in managing health conditions such as diabetes and metabolic syndrome.