Cellular Respiration - Chapter 9

Cellular Respiration - Chapter 9 - Chapter 9 Cellular...

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Chapter 9 – Cellular Respiration Living cells require transfusions of energy from outside sources to perform their many tasks. Energy flows through ecosystems while the chemicals within an ecosystem are recycled Energy flows into an ecosystem as sunlight and leaves as heat. Energy flow: Light => organic molecules => ATP + heat ---Oxygen is an energy rich molecule--- Respiration: An Overview Cellular respiration and fermentation are catabolic pathways – both are energy-producing mechanisms because they oxidize organic fuels. o Fermentation pathway in which both electron donors acceptors are organic – is only used in cases where oxygen is not present and in organisms that cannot do cellular respiration NO ATP production Organic electron donors and acceptors Partial deprivation of sugars that occurs without the use of oxygen o Cellular respiration – generates electrons by moving food molecules >>Aerobic Respiration where oxygen is consumed as a reactant along with organic fuel<< Most efficient catabolic pathway Catabolism of organic molecules ATP production Inorganic electron acceptor – many times it is oxygen The removal of energy from organic molecules and storing it as ATP Organic Compounds + Oxygen CO 2 + Water + Energy C 6 H 12 O 6 + 6 O 2 => 6 CO 2 + 6 H 2 O + Energy (ATP + heat) How much energy is there?? ΔG = -686 kcal/mol of sugar. The ATP generated is used for work and then regenerated.
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Redox: A Brief Review How do the catabolic pathways that decompose glucose and other organic fuels yield energy? - The relocation of electrons releases energy stored in organic molecules and this energy is ultimately used to synthesize ATP. Redox reactions release energy when electrons move closer to electronegative atoms. o Redox reactions (a.k.a. Oxidation-reduction reactions) These are chemical reactions which involve a partial or complete transfer of electrons from one reactant to another. This is a combustion reaction that gives off heat as energy. All combustion reactions are redox reactions . Oxidation – The loss of electrons from one substance. Reduction – The addition of electrons to another substance. Negatively charged electrons added to an atom reduce the amount of positive charge of that atom. **Bonds here are non-polar covalent bonds because of the equally shared electrons** Generalized redox reaction Xe - + Y X + Ye - Xe - is oxidized to X and Y is reduced to Ye - >>The oxidizing agent is the electron acceptor. X is the reducing agent, and Y is the oxidizing agent >>The reducing agent is the electron donor. The transfer of electrons doesn’t have to be a complete transfer (shown above) it may only be a partial transfer (e.g., combustion of methane). Many times this partial transfer changes the degree of electron sharing in covalent bonds.
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>Cellular respiration as a redox reaction< C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O Carbon and hydrogen of C 6 H 12 O 6 is oxidized to
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Cellular Respiration - Chapter 9 - Chapter 9 Cellular...

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