Copy of BIO 202 Midterm 2 Lecture Notes.pdf - Chapter 9...

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Chapter 9: Cellular Respiration * sugar + oxygen = carbon dioxide + water + energy * also called aerobic respiration because it requires oxygen * cellular respiration produces 30-32 ATP for each glucose * exergonic reaction must release more free energy than ATP hydrolysis to successfully occur * organic molecules are heavily reduced * sometimes, redox reactions involve a change in the way electrons are being shared * glucose is highly reduced, has high PE * as glucose is oxidized, its PE is reduced * carbon atoms of glucose are oxidized to form CO 2 * complete oxidation of 1 mole of glucose releases 686 kcal of energy (dG = -686 kcal/mol * in the ingestion of carbs and fats, enzymes lower the activation energy so chemical bond energy can be slowly harnessed for ATP synthesis * uncontrolled reaction vs. biological oxidization = same amount of ATP/free energy released * energy released by glucose oxidation is used to reduce electron carriers (NADH, FADH 2 ) or to synthesize ATP * NAD + (high energy) is an electron carrier that is reduced to NADH (low energy) * dehydrogenases harvest hydrogen atoms from energy rich molecules and use NAD + as a coenzyme, have a binding site for NAD + located near the substrate binding site * substrate level phosphorylation = an enzyme removes a phosphate from a phosphorylated substrate and gives it to ADP; this happens during glycolysis and the Krebs cycle, and accounts for about 10% of the ATP produced during aerobic respiration
* oxidative phosphorylation = ATP synthase catalyzes the production of ATP, using energy from the oxidation of electron carriers; accounts for about 90% of the ATP produced * glucose breakdown occurs in 4 steps: * (1) glucose is broken down to pyruvate (glycolysis) * (2) pyruvate is processed to form acetyl-CoA * (3) acetyl-CoA is oxidized to CO 2 * (4) compounds that were reduced in steps 1-3 are oxidized in reactions that lead to ATP production * glycolysis is the 1st step in glucose oxidation * glucose is broken into 2 3-carbon molecules of pyruvate, and the potential energy used to phosphorylate ADP to form ATP by substrate level phosphorylation * NAD+ is reduced to NADH (an electron carrier) * net of 2 ATPs and 2 electron carriers * energy investment phase = enzyme hexokinase adds a phosphate group to glucose and traps glucose inside the cell, and activates it * isomerase = an enzyme that rearranges a molecule into a structural isomer (i.e, glucose to fructose) * phosphofructokinase invests the 2nd ATP to add a phosphate group * aldolase cleaves into 2 different 3-carbon sugars, each containing a phosphate to raise the free energy * isomerase converts DHAP to G3P, which is used as fast as it forms, so the reaction never reaches equilibrium * energy payoff phase = an exergonic reaction that oxidizes carbonyl carbon, generating NADH and creating an activated substrate * also exergonic but less so, ATP is produced by substrate level phosphorylation * the phosphate group is moved to another carbon, destabilizing it so that it can be donated to ADP

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