BiologyOutline Ch.9

BiologyOutline Ch.9 - Chapter 9 Cellular Respiration...

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Chapter 9 – Cellular Respiration, Harvesting Chemical Energy p.162-184 Concept – Catabolic pathways yield energy by oxidizing organic fuels Metabolic pathways that release stored energy by breaking down complex molecules are called catabolic pathways. Fermentation – is a partial degradation of sugars that occurs without the use of oxygen. Aerobic respiration - oxygen is consumed as a reactant along with the organic fuel. Anaerobic respiration Cellular respiration – includes both aerobic and anaerobic, but is often referred to the aerobic process. Glucose is the fuel cells most often use. The breakdown of glucose is exergonic. Redox reactions – oxidation-reduction reactions. Loss of electrons = oxidation. Addition of electrons = reduction. Electron donor = reducing agent Electron acceptor = oxidizing agent Because oxygen is so electronegative, it is one of the most potent of all oxidizing agents. The more electronegative the atom (the stronger its pull on electrons), the more energy is required to take an electron away from it. Cellular respiration does not oxidize glucose in a single explosive step. Rather, glucose and other organic fuels are broken down in a series of steps, each one catalyzed by an enzyme. At key steps, electrons are stripped from the glucose. Each electron travels with a proton—thus, as a hydrogen atom. The hydrogen atoms are not transferred directly to oxygen, but instead are usually passed first to an electron carrier, a coenzyme called NAD+ (nicotinamide adenine dinucleotide, a derivative of the vitamin niacin). As an electron acceptor, NAD+ functions as an oxidizing agent during respiration. Dehydrogenase removes a pair of hydrogen atoms from the substrate (glucose), oxidizing it. The enzyme delivers the 2 electrons along with 1 proton to its coenzyme, NAD+. The other proton is released as a hydrogen ion (H+) into the surrounding solution. By receiving 2 negatively charged electrons but only 1 positively charged proton, NAD+ has its charge neutralized when it is reduced to NADH.
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Electron transport chain – a procedure by which respiration breaks the fall of electrons to oxygen into several energy-releasing steps. An electron transport chain breaks the “fall” of electrons into a series of smaller steps and stores some of the released energy in a form that can be used to make ATP (the rest of the energy is released as heat). In summary, during cellular respiration, most electrons travel the following “downhill” route: glucse -> NADH -> electron transport chain -> oxygen. Respiration is a cumulative function of three metabolic stages: 1. Glycolysis 2. The citric acid cycle 3. Oxidative phosphorylation: electron transport and chemiosmosis Glycolysis – which occurs in the cytosol, begins the degradation process by breaking glucose into two molecules of a compound called pyruvate. Citric acid cycle
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BiologyOutline Ch.9 - Chapter 9 Cellular Respiration...

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