Lab Paper-Cell Respiration - AP Bio Lab: Cell Respiration...

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Cell Respiration Cellular respiration is an ATP-generating process that occurs within cells. Energy is extracted from energy-rich glucose to form ATP from ADP and P i . The chemical equation describing this process is: C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + ATP Cellular respiration in the presence of O 2 is called aerobic respiration. Aerobic respiration is divided into three components: glycolysis, the Krebs cycle, and oxidative phosphorylation. Glycolysis is the decomposition (lysis) of glucose (glyco) to pyruvate or pyruvic acid. Catalyzed by enzymes, nine intermediate products are formed. At first, 2 ATP are added to change glucose in preparation for the next steps. 2 NADH coenzymes are produced when NAD + combines with two energy-rich electrons and H + , which is obtained from an intermediate molecule during the breakdown of glucose. Then 4 ATP are producedd and 2 pyruvates are formed. Krebs cycle, also known as citric acid cycle or tricarboxylic acid (TCA) cycle describes what happens to the end products from Glycolysis. Before the Krebs cycle, each pyruvate combines with coenzyme A (CoA) to produce acetyl CoA. As a result, 1 NADH and 1 CO 2 are produced. The Krebs cycle begins when acetyl CoA combines with OAA (oxaloacetate) to form citrate. Along the way, 3 NADH and 1 FADH 2 are made, and CO 2 is released. FADH 2 is a coenzyme that accepts electrons during a reaction. The CO 2 released in this process is what animals exhale when they breathe. Oxidative phosphorylation is the process of extracting ATP from NADH and FADH 2 . Electrons from NADH and FADH2 pass along an electron transport chain (ETC). ETC consists of proteins that pass these electrons from one cytochrome, a carrier protein, to the next. The electrons give up energy along each step to phosphorylate ADP to ATP. Each NADH contains enough electrons to phosphorylate 3 ATP’s, while each FADH 2 phosphorylates about 2 ATP’s. The final acceptor of the ETC is oxygen. Each ½O 2 accepts two electrons and forms water with 2 H + . To understand how the apparatus used in this experiment works, it’s important to understand the general gas law, which states: PV = nRT where P = pressure, V = volume, n = number of molecules of gas, R = gas constant, and T = temperature. The gas law describes the relationships between the varibles. If all variables held constant, both pressure and volume is directly proportional to number of molecules of gas. If all are constant, pressure is inversely proportional to the volume. If all are held constant and temperature changes, then either pressure or volume (or both) will change in direct proportion to the temperature. Gases and fluids flow from regions of high pressure to regions of low pressure. Under normal conditions, each molecule of oxygen consumed during respiration
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This note was uploaded on 03/03/2010 for the course AP BIO AP BIO taught by Professor Apbioteacher during the Spring '09 term at École Normale Supérieure.

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Lab Paper-Cell Respiration - AP Bio Lab: Cell Respiration...

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