Editing Adenosine diphosphate (section)

==Bioenergetics==
ADP cycling supplies the [[energy]] needed to do work in a biological system, the [[thermodynamic]] process of transferring energy from one source to another. There are two types of energy: [[potential energy]] and [[kinetic energy]]. Potential energy can be thought of as stored energy, or usable energy that is available to do work. Kinetic energy is the energy of an object as a result of its motion. The significance of ATP is in its ability to store potential energy within the phosphate bonds. The energy stored between these bonds can then be transferred to do work. For example, the transfer of energy from ATP to the protein [[myosin]] causes a conformational change when connecting to [[actin]] during [[muscle contraction]].<ref name=Lehninger/>

[[File:ATP-ADP.svg|thumb|The cycle of synthesis and degradation of ATP; 1 and 2 represent output and input of energy, respectively.]]It takes multiple reactions between myosin and actin to effectively produce one muscle contraction, and, therefore, the availability of large amounts of ATP is required to produce each muscle contraction. For this reason, biological processes have evolved to produce efficient ways to replenish the potential energy of ATP from ADP.<ref name="hyperphysics.phy-astr.gsu.edu">{{cite web |author =Nave, C.R. |title=Adenosine Triphosphate |year=2005 |work=Hyper Physics [serial on the Internet] |publisher=Georgia State University |url=http://hyperphysics.phy-astr.gsu.edu/hbase/biology/atp.html}}</ref>    

Breaking one of ATP's phosphorus bonds generates approximately 30.5 [[kilojoule]]s per [[Mole (unit)|mole]] of ATP (7.3 [[Calorie|kcal]]).<ref name="emc.maricopa.edu">{{cite web|author=Farabee, M.J. |title=The Nature of ATP |year=2002 |work=ATP and Biological Energy [serial on the Internet] |url=http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookATP.html |url-status=dead |archive-url=https://web.archive.org/web/20071201180511/http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookATP.html |archive-date=2007-12-01 }}</ref> ADP can be converted, or powered back to ATP through the process of releasing the chemical energy available in food; in humans, this is constantly performed via [[aerobic respiration]] in the [[mitochondrion|mitochondria]].<ref name="hyperphysics.phy-astr.gsu.edu"/> Plants use [[photosynthetic]] pathways to convert and store energy from sunlight, also conversion of ADP to ATP.<ref name="emc.maricopa.edu"/> Animals use the energy released in the breakdown of glucose and other molecules to convert ADP to ATP, which can then be used to fuel necessary growth and cell maintenance.<ref name="hyperphysics.phy-astr.gsu.edu"/>