1. Metabolism = Anabolism + Catabolism (a) Catabolism is the breakdown of complex things to yield energy (b) Anabolism is the energy-requiring build up of complex things (c) Metabolism is the sum of the biochemical reactions that take place within a living organism

2. Electron transfer (a) "All catabolic reactions involve electron transfer, which allows energy to be captured in high-energy bonds in ATP and similar molecules. Electron transfer is directly related to oxidation and reduction"

3. Oxidation (a) Oxidation is the removal of an electron from a molecule or atomOxidation (b) Oxygen, by stealing electrons from other atoms (or molecules) oxidizes those molecules (c) Oxygen is an oxidizer (d) In the process of oxidizing other atoms and molecules, oxygen is reducedreduced

4. Reduction (a) Reduction is the gain of an electron by a molecule or an atomReduction (b) Oxidation-reduction reactions always involve a change in the oxidation state of the atoms or ions involved. This change in oxidation state is due to the "loss" or "gain" of electrons. The loss of electrons from an atom produces a positive oxidation state, while the gain of electrons results in negative oxidation states.Oxidation-reduction reactions always involve a change in the oxidation state of the atoms or ions involved. This change in oxidation state is due to the "loss" or "gain" of electrons. The loss of electrons from an atom produces a positive oxidation state, while the gain of electrons results in negative oxidation states.

5. Electron acceptor (a) An electron acceptor is the substance in a chemical reaction that gains an electron (that is, is reduced)reduced (b) In catabolism, ultimately electrons must be donated from one substance (typically containing carbon) to some other substance (often oxygen)catabolism (c) The last substance receiving the electrons before their elimination from the organism is termed a final electron acceptor (in aerobic organisms the final electron acceptor is usually molecular oxygen, which is converted to water upon reception of these electrons) (d) Note that the reception of electrons by an electron acceptor in a biological system is typically associated with the gain of a bond to a hydrogen atom (H), e.g., water is H-O-H which represents a replacement of the O=O bond of molecular oxygen with H-O bond

6. Electron donor (a) An electron donor is the substance in a chemical reaction that loses an electron (that is, is oxidized)oxidized (b) The complex, energy-rich substances broken down during catabolism are termed electron donorscatabolism (c) Essentially, electrons are removed from these substances and the energy associated with those electrons is used to phosphorylate ADP to produce ATP (d) For a carbon-containing electron donor, the donation of elections typically is associated with the loss of C-H bonds and the gain of C-O bonds

7. NADH (a) The stripping of electrons from biomolecules is performed to a large extent by a compound that is abbreviated as NAD + (b) When electrons are stripped from a compound by NAD +, the electrons are stripped off in pairs (i.e., two electrons per NAD + ) (c) In addition, when electrons are stripped off of a compound by NAD +, NAD + additionally removes two protons, a.k.a., hydrogen ions, a.k.a., H + (d) This converts NAD + into NADH + H + (i.e., NADH plus one hydrogen ion) (e) Note that in such reactions NAD + serves as the electron acceptor (with NADH + H + formed upon acceptance of electrons) and the compound from which the electrons are stripped serves as the electron donor (NAD + is reduced to form NADH + H + and the electron- donating molecule is similarly oxidized)

8. ATP (a) Usually either physical or chemical sources of energy are converted into ATP (b) That is, the ultimate product of most catabolic pathways within cells is the generation of ATPcatabolic pathways (c) It is the stripping of biomolecules of their electrons that, either directly or indirectly, turns these complex molecules into simpler ones (e.g., ultimately water and carbon dioxide) (d) The energy associated with these removed electrons is then extracted to supply the energy necessary to phosphorylate ADP to make ATP (e) Some of that energy is then liberated to power anabolic reactions as ATP is converted back to ADP in a dephosphorylation reaction

9. REDOX – OXIDATION/REDUCTION OXIDATION IS LOSS REDUCTION IS GAIN

10. OXIDIZING AGENT 1) IS REDUCED 2) CAUSES OXIDATION BY ACCEPTING e¯ 3) DECREASE IN CHARGE (OX #)

11. REDUCING AGENT 1) IS OXIDIZED 2) CAUSES REDUCTION BY PROVIDING e¯ 3) INCREASE IN CHARGE (OX #

12. SUMMARY OXIDATION -LOSS OF e¯ - GAIN OF O₂ - LOSS OF H₂ - RESULTS IN MANY C-O BONDS - RESULTS IN A COMPD. WITH LOWER POTENTIAL ENERGY

13. REDUCTION -GAIN OF e¯ - LOSS OF O₂ - GAIN OF H₂ - RESULTS IN MANY C-H BONDS - RESULTS IN A COMPD. WITH HIGHER POTENTIAL ENERGY