A 70 -kg adult human (154 lb) could meet his or her entire...

A 70 -kg adult human $(154$ lb) could meet his or her entire energy needs for one day by eating 3 moles of glucose $(540 \mathrm{g}) .$ (We don't recommend this.) Each molecule of glucose generates 30 ATP when it is oxidized to $\mathrm{CO}_{2}$. The concentration of ATP is maintained in cells at about $2 \mathrm{mM}$, and a $70-\mathrm{kg}$ adult has about 25 liters of intracellular fluid. Given that the ATP concentration remains constant in cells, calculate how many times per day, on average, each ATP molecule in the body is hydrolyzed and resynthesized.

Key Concepts

Molar Concentration Calculations

This concept deals with the quantitative relationships between the amount of substance, its concentration, and the volume in which it is distributed. In the context of the problem, calculating the number of ATP molecules present in a given volume of intracellular fluid, and relating it to the total ATP turnover, demonstrates the importance of understanding stoichiometric relationships in biological systems.

Stoichiometry of Glucose Oxidation

Stoichiometry in this context involves the quantitative comparison of reactants and products in a biochemical reaction. The oxidation of glucose to carbon dioxide produces a fixed number of ATP molecules per glucose molecule, and using this ratio, one can calculate the total ATP generated. This helps in determining how many cycles of ATP turnover occur over a given period based on energy supply from glucose oxidation.

Energy Metabolism

This concept involves the biochemical pathways by which cells convert nutrients into usable forms of chemical energy. It encompasses the oxidation of substrates like glucose to produce ATP, the universal energy currency in cells, which drives most physiological processes. Understanding energy metabolism provides the framework for how organisms maintain energy balance and support cellular functions.

ATP Turnover

ATP turnover refers to the continuous process of ATP hydrolysis and subsequent resynthesis that occurs within cells. Despite the ATP pool remaining relatively constant in concentration, individual ATP molecules are rapidly cycled to sustain the energy demands of the cell. This rapid turnover illustrates the dynamic equilibrium necessary to maintain cellular energy homeostasis.

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