The Physics Factbook™
Edited by Glenn Elert -- Written by his students
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|Bibliographic Entry||Result |
|Barnes, Sue & Helena Curtis. Biology, Fifth Edition. New York: Worth, 1989: 180-182.||"In the course of the reaction, about 7 kilocalories of energy are released per mole."||29 kJ |
|"Adenosine Triphosphate." Encarta. Redmond, WA: Microsoft, 1997-2000.||"With the release of the end phosphate group, 7 kilocalories of energy become available for work and the ATP molecule becomes ADP."||29 kJ |
|Farabee, M.J. ATP and Biological Energy. On-Line Biology Book. Estrella Mountain Community College, 2000.||"Energy is stored in the covalent bonds between phosphates, with the greatest amount of energy (approximately 7 kilocalories) in the bond between the second and third phosphate groups."||29 kJ |
|Hinkle, Peter & Richard McCarthy. "How cells make ATP." Scientific American. March 1978: 238, 104-117||"The amount of energy needed to form ATP depends on the chemical environment, but is never more than about 15 kilocalories per mole"||63 kJ |
|Campbell, Neil. Biology, Third Edition. Benjamin Cummings, 1993: 97-101.||"The reaction is exergonic, and under laboratory conditions, releases 7.3 kcal of energy per mole of ATP hydrolyzed"||31 kJ |
(per mole, lab)
(per mole, cell)
|Bray, Dennis. Cell Movements. New York: Garland, 1992: 6.||"What is this power requirement in terms of ATP molecules, the principle currency of energy in the cell? Hydrolysis of one gram mole of ATP releases about 470 kJ of useful energy; hydrolysis of a single ATP molecule, about 10-19 J."||470 kJ |
(per gram mole)
All of the biosynthesis activities of the cell, many of itstransport processes and a variety of other activities requireenergy. Energy is defined as the capacity to do work. AdenosineTriphosphate (ATP), a molecule found in all living organisms isthe immediate source of usable energy for body cells and theirfunction. ATP is built up by the metabolism of food in cell'smitochondria. ATP is characterized as a coenzyme because the energyexchanging function of ATP and the catalytic function of enzymesare intimately connected.
ATP is made up of the nitrogenous base adenine, the five-carbonsugar ribose and three phosphate groups. Three phosphate units(triphosphate), each made up of one phosphorus atom and four oxygenatoms, are attached to the ribose. The two bonds between the threephosphate groups are relatively weak and yield their energy readilywhen split by enzymes. Inside a cell the ATP molecule is splitat one of the high energy bonds, releasing the energy to powercellular activities. Adenosine diphosphate (ADP) and phosphorus(P) are produced in the process. With the release of the end phosphategroup, 7 kilocalories (under laboratory conditions) of energybecome available for work.
ATP + H2O → ADP + Phosphate
ATP needs to be regenerated continuously by the recombiningof ADP and P. From the foods and beverages people eat and drinkand through the process of digestion and absorption, cells breakdown several types of compounds to release enough energy to causeADP and P to recombine and replenish ATP stores. These compoundsare phosphocreatine (PCr), carbohydrates, fats and proteins.
ATP is the most frequent molecule that supplies energy in coupledreactions. In coupled reactions, endergonic reactions or transportprocesses are linked to exergonic reactions that provide a surplusof energy. This makes the entire process exergonic and able toproceed spontaneously. The covalent bonds linking the two phosphatesto the rest of the molecule are easily broken, which release energyin the amount of 7 kilocalories per mole (under laboratory conditions).
Most of the energy consuming reactions in cells are poweredby the conversion of ATP to ADP; they include the transmissionof nerve signals, the movement of muscles, the synthesis of proteinand cell division.
Amber Iqbal -- 2000
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