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RESPIRATION. Energy in food. Carbohydrates (17 kJ g -1 ) Proteins (17 kJ g -1 ) Lipids (34 kJ g -1 ) These are sources of reduced carbon This can supply hydrogen atoms protons (H + ) + electrons (e - ). © 2010 Paul Billiet ODWS. Energy transformations.
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Energy in food • Carbohydrates (17 kJ g-1)Proteins (17 kJ g-1)Lipids (34 kJ g-1) • These are sources of reduced carbon • This can supply hydrogen atoms protons (H+) + electrons (e-) © 2010 Paul Billiet ODWS
Energy transformations Light Chemical (mostly in chemical bonds) Chemical Heat Chemical Kinetic (movement) Chemical Chemical COUPLED REACTIONSe.g. Food ATP © 2010 Paul Billiet ODWS
Inorganic phosphate High energy bond The energy in Adenosine Triphosphate (ATP) ADP + Pi ATP + H2O E = + 30.5 kJ mol-1 ADENOSINE P P P © 2010 Paul Billiet ODWS
A stepwise energy release is needed Complete oxidation of glucose C6H12O6 + 6O2 6CO2 + 6H2O E = 2880 kJ mol-1 Complete oxidation of a fat (lipid) C18H34O2 + 25.5O2 18CO2 + 17H2O E = 9800 kJ mol-1 © 2010 Paul Billiet ODWS
Respiration is efficient • This is too much to handle all at once • Energy is released step by step • Coupled to ATP synthesis • The energy in 1 molecule of glucose is used to synthesise 36 molecules of ATP • 37.5 % efficient • This is a very efficient energy conversion • Because the release of the energy from the food molecules is done stepwise © 2010 Paul Billiet ODWS
Coupling the energy released from glucose to ATP Two reaction pathways • GLYCOLYSISin the cytoplasm • KREB'S CYCLEin mitochondria of eukaryotes (in the cytoplasm of prokaryotes) © 2010 Paul Billiet ODWS