Heart muscle gets most of the ATP needed to power its...

Heart muscle gets most of the ATP needed to power its continual contractions through oxidative phosphorylation. When oxidizing glucose to $\mathrm{CO}_{2}$, heart muscle consumes $\mathrm{O}_{2}$ at a rate of $10 \mu \mathrm{mol} / \mathrm{min}$ per $\mathrm{g}$ of tissue, in order to replace the ATP used in contraction and give a steady-state ATP concentration of $5 \mu \mathrm{mol} / \mathrm{g}$ of tissue. At this rate, how many seconds would it take the heart to consume an amount of ATP equal to its steady-state levels? (Complete oxidation of one molecule of glucose to $\mathrm{CO}_{2}$ yields 30 ATP, 26 of which are derived by oxidative phosphorylation using the 12 pairs of electrons captured in the electron carriers NADH and FADH $_{2}$.)

Key Concepts

Oxidative Phosphorylation

Oxidative phosphorylation is the process by which cells produce ATP using energy derived from electrons transferred through the electron transport chain in the mitochondria. This process links the oxidation of nutrients to ATP synthesis, making it fundamental for supplying the energy required for various cellular functions, particularly in energy-demanding tissues like the heart.

ATP Turnover and Steady-State Concentration

ATP turnover refers to the continual synthesis and use of ATP within cells to meet energy demands. Steady-state concentration is the balance point where ATP production exactly matches consumption. Understanding these concepts is crucial to grasp how cells maintain constant energy levels despite ongoing high rates of ATP usage during processes such as muscle contraction.

Reaction Stoichiometry in Cellular Respiration

Reaction stoichiometry in cellular respiration describes the quantitative relationships between reactants and products in the metabolic pathways that convert substrates like glucose into energy. For example, knowing the number of ATP molecules generated per molecule of glucose oxidized helps in quantifying the efficiency of ATP production via oxidative pathways.

Oxygen Consumption in Metabolic Processes

Oxygen consumption is integral to aerobic metabolism because oxygen serves as the final electron acceptor in the electron transport chain. The rate at which oxygen is used is directly related to the pace of ATP production during oxidative phosphorylation. Thus, understanding oxygen consumption provides insights into the metabolic rate and energy efficiency of cells, especially in high-energy-demand tissues like the heart.

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