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Regulation of Metabolic Pathways:- Living Cells Maintain a Dynamic Steady State

المؤلف:  David L. Nelson، Michael M. Cox

المصدر:  Lehninger Principles of Biochemistry

الجزء والصفحة:  571

2026-06-09

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Regulation of Metabolic Pathways:- Living Cells Maintain a Dynamic Steady State

Fuels such as glucose enter a cell, and waste products such as CO₂ leave, but the mass and the gross composition of a typical cell do not change appreciably over time; cells and organisms exist in a dynamic steady state, but not at equilibrium with their surroundings. At the molecular level, this means that for each metabolic reaction in a pathway, the substrate is provided by the preceding reaction at the same rate at which it is con verted to product. Thus, although the rate of metabolite flow, or flux, through this step of the pathway may be high, the concentration of substrate, S, remains con stant. For the reaction

when v1=v2, [S] is constant. When the steady state is disturbed by some change in external circumstances or energy supply, the temporarily altered fluxes through individual metabolic pathways trigger regulatory mechanisms intrinsic to each pathway. The net effect of all these adjustments is to return the organism to a new steady state—to achieve homeostasis.

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