![]() ![]() Hydrolysis of ATP to ADP causes a conformational change-the protein changes shape-that generates a mechanical force. Motor proteins are one shape when bound to ATP. The molecular details of muscle contraction are shown below. DNA replication and protein synthesis are especially high in these cells.ĪTP powers the “motor” proteins that do the small-scale work of shuttling cargo around inside of cells, as well as the large-scale work of making our muscles contract. Some cells, like the ones that make up our skin and the lining of our digestive tract, are actively dividing to replace cells that are lost every day. Most of our cells steadily make proteins and carry out other repairs as part of their routine maintenance. The illustration shows how an enzyme (tRNA synthetase) uses ATP to "charge" a tRNA molecule, attaching an amino acid that will be used for building a protein. The biggest users of ATP are listed below. In other words, the energy from ATP can be used to drive a chemical reaction, move something, or push a molecule from one side of a membrane to another. The work that ATP does falls into three general categories: chemical, mechanical, and transport. In these reactions, enzymes oversee the transfer of energy from ATP hydrolysis to the formation of another chemical bond. A working muscle cell makes and uses about 10 million molecules of ATP every second!Įnergy from ATP is used to fuel all manner of chemical reactions, including those required for copying DNA and building proteins. The cell can make and break ATP extremely quickly. Getting the energy back out requires a protein (or in some cases RNA) that (1) breaks the third phosphate group off and (2) uses the energy released, like when a spring uncoils, to do something: drive a chemical reaction, move part of the protein, or transport something (see below). This bond is a source of potential chemical energy, and it’s kind of like a compressed spring. The word triphosphate indicates that the molecule has 3 phosphate groups.ĪTP stores energy within the bonds between phosphate groups, especially the second and third. ![]() To “charge” ADP, the cell adds a third phosphate group, converting ADP to ATP. The word diphosphate indicates that the molecule has 2 phosphate (PO 3) groups. Like a rechargeable battery, ATP can also be recharged and reused.ĪDP, the “uncharged” version of the molecule, stands for adenosine diphosphate. The cell doesn’t have to make ATP from scratch every time it needs some energy. ![]()
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