Weak Forces Restrict Organisms to a Narrow Range of Environmental Conditions

The central role of weak forces in biomolecular interactions restricts living systems to a narrow range of physical conditions. Biological macromolecules are functionally active only within a narrow range of environmental conditions, such as temperature, ionic strength, and relative acidity. Extremes of these conditions disrupt the weak forces essential to maintaining the intricate structure of macromolecules. The loss of structural order in these complex macromole-cules, so-called denaturation, is accompanied by loss of function (Figure 1.17). As a consequence, cells cannot tolerate reactions in which large amounts of energy are released. Nor can they generate a large energy burst to drive energy-requiring processes. Instead, such transformations take place via sequential series of chemical reactions whose overall effect achieves dramatic energy changes, even though any given reaction in the series proceeds with only mod-

FIGURE 1.17 • Denaturation and renaturation of the intricate structure of a protein.

FIGURE 1.17 • Denaturation and renaturation of the intricate structure of a protein.

Denaturation And Renaturation

The combustion of glucose: C6H^O6 + 6O2

(a) In an aerobic cell

6CO2 + 6H2O

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(b) In a bomb calorimeter

(a) In an aerobic cell

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