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Ok Cookie options. ATP is a highly unstable molecule. To harness the energy within the bonds of ATP, cells use a strategy called energy coupling. Energy Coupling : Sodium-potassium pumps use the energy derived from exergonic ATP hydrolysis to pump sodium and potassium ions across the cell membrane.
Cells couple the exergonic reaction of ATP hydrolysis with the endergonic reactions of cellular processes. For example, transmembrane ion pumps in nerve cells use the energy from ATP to pump ions across the cell membrane and generate an action potential.
When ATP is hydrolyzed, it transfers its gamma phosphate to the pump protein in a process called phosphorylation. During cellular metabolic reactions, or the synthesis and breakdown of nutrients, certain molecules must be altered slightly in their conformation to become substrates for the next step in the reaction series. In the very first steps of cellular respiration, glucose is broken down through the process of glycolysis. ATP is required for the phosphorylation of glucose, creating a high-energy but unstable intermediate.
This phosphorylation reaction causes a conformational change that allows enzymes to convert the phosphorylated glucose molecule to the phosphorylated sugar fructose. Fructose is a necessary intermediate for glycolysis to move forward. Some energy in ATP is released to do work, such as move muscles or force a seedling out of the ground.
At other times, ATP gives up its energy to a nonspontaneous synthetic reaction, such as the formation of sucrose. ATP is used to close the energy gap between energy-releasing reactions food breakdown and energy-requiring reactions synthesis. When a molecule of fatty acid is burned, energy is given off. Some of this energy is trapped in molecules of ATP, and some is lost in the form of heat. Each ATP molecule can then be transported elsewhere within the cell and used where needed.
The energy-carrying part of an ATP molecule is the triphosphate "tail". Three phosphate groups are joined by covalent bonds.
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