1. Thermodynamics and Metabolism

2. 2 Metabolism Metabolism: all chemical reactions occurring in an organism Anabolism: chemical reactions that expend energy to make new chemical bonds Catabolism: chemical reactions that harvest energy when bonds are broken

3. 3 Flow of Energy Energy: the capacity to do work -kinetic energy: the energy of motion -potential energy: stored energy Energy can take many forms: mechanicalelectric current heatlight

4. 4 Flow of Energy Potential energy stored in chemical bonds can be transferred from one molecule to another by way of electrons. oxidation: loss of electrons reduction: gain of electrons redox reactions are coupled to each other.

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6. 6 Laws of Thermodynamics First Law of Thermodynamics – energy cannot be created or destroyed -energy can only be converted from one form to another For example: sunlight energy chemical energy photosynthesis

7. 7 Laws of Thermodynamics Second Law of Thermodynamics: disorder is more likely than order entropy: disorder in the universe The 2 nd Law of Thermodynamics states that entropy is always increasing.

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9. 9 Laws of Thermodynamics Free energy: the energy available to do work -denoted by the symbol G (Gibb’s free energy) enthalpy: energy contained in a molecule’s chemical bonds free energy = enthalpy – (entropy x temp.) G = H - TS

10. 10 Laws of Thermodynamics Chemical reactions can create changes in free energy. When products contain more free energy than reactants  G is positive. When reactants contain more free energy than products  G is negative.

11. 11 Laws of Thermodynamics Chemical reactions can be described by the transfer of energy that occurs: endergonic reaction: a reaction requiring an input of energy -  G is positive exergonic reaction: a reaction that releases free energy -  G is negative

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13. 13 Laws of Thermodynamics Most reactions require some energy to get started. activation energy: extra energy needed to get a reaction started -destabilizes existing chemical bonds -required even for exergonic reactions catalysts: substances that lower the activation energy of a reaction

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15. 15 Energy Currency of Cells ATP = adenosine triphosphate -the energy “currency” of cells ATP structure: -ribose, a 5-carbon sugar -adenine -three phosphates

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17. 17 Energy Currency of Cells ATP stores energy in the bonds between phosphates. Phosphates are highly negative, therefore: -the phosphates repel each other -much energy is required to keep the phosphates bound to each other -much energy is released when the bond between two phosphates is broken

18. 18 Energy Currency of Cells When the bond between phosphates is broken: ATP ADP + P i energy is released ADP = adenosine diphosphate P i = inorganic phosphate This reaction is reversible.

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20. 20 Energy Currency of Cells The energy released when ATP is broken down to ADP can be used to fuel endergonic reactions. The energy released from an exergonic reaction can be used to fuel the production of ATP from ADP + P i.