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  • Q: In a test tube, why to chemical reactions occur? - likely have heard of two major forms of energy Q: Which is it for chemical reactions? Q: Where is the energy stored for chemical reactions?
  • Q: What other “law” is that similar to? - law of constant mass
  • Q: How much energy does a bond hold? Q: What would be a good way to test that out? - describe the experiment that was done 1) Difficult to look at one molecule  easier for a mole of molecules 2) Zap them with energy 3) Determine how much energy was used
  • Q: Given single and double bonds, which do you suppose requires more energy to break?
  • - we have reactions that release energy and form energy (exothermic and endothermic) Q: How does that work?
  • - energy of chemical reactions can be visualized in a graphical representation 1) x-axis represents progress of the reaction 2) y-axis represents energy of the components -need to indicate energy of the reactants and products Q: Given this difference between reactants and products, what type of reaction is depicted here?
  • - energy of chemical reactions can be visualized in a graphical representation 1) x-axis represents progress of the reaction 2) y-axis represents energy of the components -need to indicate energy of the reactants and products Q: Given this difference between reactants and products, what type of reaction is depicted here?
  • Q: But we’re continually losing heat... is the universe going to break down and collapse to heat?
  • Q: What is the purpose of metabolism? - to utilise the energy it produces
  • Q: How much work energy is available in a reaction in equilibrium? - 0
  • Q: What happens to the energy? - it needs to be focused
  • Take a look at the triphosphate. Q: What is the overwhelming charge? - negative Q: Why is this unstable? - likes repel
  • Q: What type of reaction is this? - hydrolysis - catabolism
  • Q: What type of reaction is this? - hydrolysis - catabolism
  • Q: What reaction do you know of that would be classified as redox? - NaCl
  • - redox is the condensation of the two terms reduction and oxidation - clearly, these reactions are coupled (can’t have one without the other)

Transcript

  • 1. Where does it come from?
  • 2. Energy the ability to do work kinetic – energy due to movement potential – stored energy Chemical potential energy is stored up in the bonds of a molecule.
  • 3. First Law of Thermodynamics The total amount of energy in the universe is constant. Energy cannot be created or destroyed.
  • 4. H+ H+ H+ H+ H+ - - - - -
  • 5. Energy Bond energy is measured in kJ / mol (kilojoules per mole). The greater the bond energy, the more chemically stable the bond. Bond stability is not related to chemical reactivity. Bond Type Average Bond Energy (kJ/mol) H-H 436 C-H 411 O-H 459 N-H 391 C-C 346 C-O 359 C=O 799 O=O 494
  • 6. Energy exothermic reactions – energy released endothermic reactions – energy absorbed Energy is required to break bonds. Energy is released when forming bonds. breaking > forming breaking < forming endothermic exothermic
  • 7. Potential Energy Diagram
  • 8. Animations Transition State Animation The “molecule” with the highest level of energy is known as the transition state. It is the stage in between the reactants and the products
  • 9. Potential Energy Diagram EXOTHERMIC REACTION
  • 10. Cellular Energy Energy transfer in a cell depends on bond energy. Many reactions release heat, which dissipates. The energy which is useful is called Gibbs free energy. This is related to enthalpy.
  • 11. Potential Energy Diagram ∆G
  • 12. Gibbs Free Energy (G) ∆G = Gfinal – Ginitial ∆G = Gproducts – Greactants ∆G is negative for spontaneous reactions ∆G is positive for reactions that require energy
  • 13. Gibbs Free Energy Exergonic reactions are spontaneous, - ∆G Endergonic reactions are not spontaneous, + ∆G C6H12O6 + 6O2  6CO2 + 6H2O ∆G = -2870 kJ/mol 6CO2 + 6H2O  C6H12O6 + 6O2 ∆G = +2870 kJ/mol
  • 14. Second Law of Thermodynamics The universe is becoming more disordered. Entropy is a measure of randomness / disorder. greater entropy = greater disorder C6H12O6 + O2  CO2 + H2O + energy
  • 15. Equilibrium Equilibrium reactions convert back and forth with minimal energy. For equilibrium reactions: ∆G = 0
  • 16. What is the main source of energy for a cell?
  • 17. Cellular Energy Two main types of energy related reactions: 1.phosphorylation 2.reduction-oxidation (redox) reactions
  • 18. 1. Phosphorylation phosphorylation - the transfer of a phosphate group to another molecule This molecular transfer equates to a transfer of energy and is carried out by an enzyme.
  • 19. 1. Phosphorylation ATP ADP + Pi + energy H2O ∼∆G = -31 kJ/mol ATPase
  • 20. 1. Phosphorylation
  • 21. 2. Redox Reactions redox reactions - reactions involving electron transfer
  • 22. 2. Redox Reactions reduction – chemical reaction where an atom gains electrons oxidation – chemical reaction where an atom loses electrons Loss Gain Electron Electron Oxidation Reduction LEO the lion says GER
  • 23. 2. Redox Reactions reducing agent – substance that LOSES electrons; it causes the other substance to be reduced oxidizing agent – substances that GAIN electrons; it causes the other substance to be oxidized
  • 24. Redox in the Cell Many metabolic processes consist of chains of redox reactions. A- A B- B C- C D D-