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Lecture 10

Lecture 10: "Cellular Respiration I"

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Biology 1002B
Tom Haffie

Biology Lecture No. 10: Cellular Respiration I th Wednesday February 8 , 2012 Cellular Respiration: -Respiration is an overall exergonic process which yields a negative change in Gibbs’ Free Energy (-∆G). -Out of all metabolic processes, cellular respiration has a fundamental role in biological function. It occurs in all known organisms. Metabolic Pathways: -Respiration consists of two major types of metabolic pathways: Catabolic pathways and anabolic pathways. -Catabolic pathways involve the breakdown of molecules and release of free energy. The overall pathway is exergonic (-∆G). -Anabolic pathways involve the synthesis of more complex molecules out of simpler forms. Examples of such pathways include all biosynthetic pathways like photosynthesis. The overall pathway is endergonic (+∆G). ATP & ADP Cycle: -Catabolic pathways drive the conversion of ADP + Pi to ATP. -When the free energy of ATP is coupled with anabolic pathways, the energy is released and leaves behind the original reactants, ADP and Pi, waiting to begin the cycle again. Glucose Breakdown: -Recall that food can be the equivalent of fuel as molecules for consumption (like glucose, amino acids and fatty acids) contain lots of carbon-hydrogen bonds. -Especially in glucose, there is a lot of free energy associated with such molecules. In the reaction for cellular respiration, C6H12 6 + 6O 2 6CO 2 + 6H O2 glucose is oxidized to CO an2 oxygen is reduced to water. It can be said that CO is much more oxidant than glucose. 2 Respiration & Controlled Combustion: -Cellular respiration essentially comprises of extracting energy from glucose by way of controlled combustion. The change in free energy is the same regardless of whether the combustion of glucose is controlled or not (686kCal/mol). - The only difference is that respiration has many small activation energies where direct burning has just one large E a That is because respiration involves transferring energy to electron carriers and uncontrolled combustion has all the energy released as heat, none is stored. NAD As An Electron Shuttle: -Where NADP transports electrons in anabolic and biosynthetic reactions, NAD (Nicotinamide adenine dinucleotide) is the main energy carrier in catabolic reactions like cellular respiration. (NAD + 2e + H + NADH) Overview Of Respiration: -Cellular respiration comprises of three main processes in this particular order: Glycolysis (Breakdown/Oxidation of Glucose), Citric Acid Cycle (Production of CO ), a2d the Electron Transfer System & Oxidative Phosp
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