ATP – Cellular Energy Organisms/cells are endergonic systems must have energy for  Mechanical work  Transport work  Chemical work Ribose, Adenine, 3 phosphates

ATP – Cellular Energy Adenosine tri phosphate  3 phosphate groups covalently bonded  Can be removed by hydrolysis  High energy bonds Negative phosphates repel one another, easy to remove Compressed spring analogy Hydrolysis --- G = -7.3 kcal/mol Exergonic Spontaneous Free energy | V Instability of its P bonds makes ATP an excellent energy donor

ATP = Energy…. How? Work of life is done by energy coupling  use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions ++ energy + + digestionsynthesis

ATP – Energy Coupling

How does ATP transfer energy? P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O 7.3 energy + P O–O– O–O– O –O–O ATP → ADP  releases energy ∆G = -7.3 kcal/mole Fuel other reactions Phosphorylation  released P i can transfer to other molecules destabilizing the other molecules  enzyme that phosphorylates = “kinase” ADPATP

An example of Phosphorylation… Building polymers from monomers  need to destabilize the monomers  phosphorylate! C H OH H HOHO C C H O H C + H2OH2O kcal/mol C H OH C H P + ATP + ADP H HOHO C + C H O H CC H P + PiPi “kinase” enzyme -7.3 kcal/mol -3.1 kcal/mol enzyme H OH C H HOHO C synthesis

ATP – Drives Cellular Work Phosphorylation  makes molecule less stable, more likely to react  Conformational change Conformational Change Increased Reactivity ATP is replenished in cellular respiration ADP + Pi  ATP

Cells can’t store ATP  good energy donor, not good energy storage too reactive transfers P i too easily  carbohydrates & fats are long term energy storage ATP / ADP cycle A working muscle recycles over 10 million ATPs per second ATP ADP PiPi kcal/mole cellular respiration