Biology 1002B Chapter Notes - Chapter 6: Citric Acid Cycle, Cellular Respiration, Oxidative Phosphorylation

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Cellular respiration: the process by which energy-rich molecules are broken down to produce
ATP
6.1a Food is Fuel
Good fuel molecules have an abundance of C-H bonds
o E- that is farther away from nucleus contain more energy than e- closer to nucleus
o E- in C-H bond are not strongly held by C or H, which means e- can be easily
removed to do work
o CO2 contain less potential energy because O is electronegative and hold e- closer to
nucleus, thus harder to remove e-
Fats contain more energy per unit of weight than proteins and carbohydrates because it is
almost entirely C-H bonded
6.1b Coupled Oxidation-Reduction Reactions are Central to Energy Metabolism
Potential energy released when molecules are oxidized (lose e-)
E- released from oxidized molecule is used to reduce another molecule (gain e-)
Many oxidation reactions involve O2, but others do not
Gain or loss of e- is not always complete
o What changes is degree to which e- are shared between two atoms
o CH4 + 2O2 ---> CO2 + 2H2O + energy
o In the reactant, e- in methane is shared equally in C-H bond
o In the product, e- in CO2 is more closer to O, so C has partially lost its e-, and
methane is oxidized
o In the reactant, e- in O2 is shared equally in O=O bond
o In the product, e- in H2O is closer to O, so O has partially gained e-, and O2 is
reduced
o Energy is released as e- in C-H move closer to O that form CO2
6.1c Cellular Respiration is Controlled Combustion
Energy of C-H bonds not liberated suddenly to produce heat; energy is transferred to
carrier molecules
Dehydrogenase: enzyme that oxidizes food and transfers e- to energy carrier
o Dehydrogenase removes 2H from substrate, and transfers 2 e- and one H+ to NAD+
o NAD+ (electron carrier) is reduced to NADH
o Efficiency of enzyme-catalyzed transfer of energy from food to NAD+ is very high
Goal of cellular respiration - transform potential energy in food into ATP
6.2a Cellular Respiration Can be Divided into Three Phases
1. Glycolysis
o Enzymes break down one glucose into two pyruvates
o Some ATP and NADH is synthesized
2. Pyruvate oxidation and citric acid cycle
o Acetyl-CoA is formed from oxidation of pyruvate and is completely oxidized to CO2
o Some ATP and NADH is synthesized
3. Oxidative phosphorylation
o NADH synthesized in glycolysis and citric acid cycle is oxidized
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Document Summary

Cellular respiration: the process by which energy-rich molecules are broken down to produce. Fats contain more energy per unit of weight than proteins and carbohydrates because it is almost entirely c-h bonded. In the reactant, e- in methane is shared equally in c-h bond. In the product, e- in co2 is more closer to o, so c has partially lost its e-, and methane is oxidized. In the reactant, e- in o2 is shared equally in o=o bond. In the product, e- in h2o is closer to o, so o has partially gained e-, and o2 is reduced: energy is released as e- in c-h move closer to o that form co2. Goal of cellular respiration - transform potential energy in food into atp. 6. 2b the mitochondrion is the site of cellular respiration in eukaryotes. In bacteria and archaea, glycolysis and citric acid cycle occur in cytosol; oxidative phosphorylation occurs on internal membranes.

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