Oxidative Phosphorylation Study Guide

Oxidative Phosphorylation How are the electrons in NADH and FADH2 used to make ATP during cellular respiration? Why? The final phase of cellular respiration is oxidative phosphorylation. Both the electron transport chain and chemiosmosis make up oxidative phosphorylation. During this phase of cellular respiration, all of the NADH and FADH2 that were produced in other phases of cellular respiration (glycolysis, the link reaction, and Krebs cycle) are used to make ATP. The process occurs in the protein complexes embedded in the inner mitochondrial membrane. Model 1 – Electron Transport Chain Outer Mitochondrial Membrane H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ Intermembrane Space H+ H+ H+ H+ H+ Embedded protein channels H+ H+ Inner Mitochondrial Membrane High potential energy electron H+ H+ H+ NADH NAD+ + H+ FADH2 FAD+ + 2H+ 2H2O O2 + 4H+ Mitochondrial Matrix 1. Consider the membranes illustrated in Model 1. Circle a section of the mitochondria below where this site might be located. The highest concentration of hydrogen ion (H+) is located in the intermembrane space in Model 1. According to Model 1, the hydrogen ions reach this area through protein channels. Energy is required to move the hydrogen ions across the membrane in the direction indicated in Model 1 because it is needed as the hydrogen ions are pumped against the concentration gradient. NADH and FADH2 carry these high potential energy electrons. These electron acceptor molecules come from Glycolysis, Link Reaction, and Krebs Cycle. When the electrons are released from the electron acceptor molecules, hydrogen ions (H+) are also produced. The release of an electron from one of these electron acceptor molecules is oxidation due to the loss of electrons. Oxygen is the final acceptor after the electron has moved through the electron transport chain. Water (H2O) is formed as a final product of the electron transport chain. There is no ATP produced in the electron transport chain. There is no ATP used in the electron transport chain. Model 2 – Chemiosmosis Outer Mitochondrial Membrane H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ Intermembrane Space H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ Inner Mitochondrial Membrane ATP Synthase ATP H+ Mitochondrial Matrix ADP + Pi 8. Describe the movement of hydrogen ions through the membrane illustrated in Model 2. The movement of hydrogen ions through the membrane illustrated in Model 2 is that hydrogen ions (H+) move from the intermembrane space through the inner mitochondrial membrane. They then move to the mitochondrial matrix after. 9. Would free energy be required for the hydrogen ions to move in the direction shown in Model 2? Explain your reasoning. Free energy would not be required for the hydrogen ions to move in the direction shown in Model 2. This is because the hydrogen ions are diffusing down the concentration gradient, therefore requiring no free energy. 10. What is the name of the embedded protein that provides a channel for the hydrogen ions to pass through the membrane? ATP Synthase is the embedded protein that provides a channel for the hydrogen ions to pass through the membrane. 11. The flow of hydrogen ions through the protein channel provides free energy to do work. What process in Model 2 requires energy? The process in Model 2 that requires energy is the production of ATP from ADP. Pi will also require energy. During oxidative phosphorylation, ADP is adding a phosphate group to make a ATP. The total number of ATP molecules that might be produced in this phase of cellular respiration from one glucose molecule would be 34 ATP molecules. This is because there are a total of 10 NADH from Glycolysis (2), Link Reaction (2), and Krebs Cycle (6). This is multiplied by 3 ATP making a total of 30 ATP. Then, we would have 4 more ATP molecules from 2 FADH2 from the Krebs Cycle multiplied by 2 ATP. Considering all the stages of cellular respiration, assuming ideal circumstances, there would be 38 ATP molecules produced from one glucose molecule. The amount of ATP made for every step is as follows; Glycolysis (2), Link Reaction (0), Krebs Cycle (2), and Oxidative Phosphorylation (30). The role of molecular oxygen (O2) in aerobic respiration is that it is crucial to it due to the combination of hydrogen ions and electrons that are carried by NADH and FADH2. Without molecular oxygen (O2) to pick up these electrons as they complete the electron transport chain, it would not properly function. Glycolysis Oxidative Phosphorylation Link Reaction Krebs Cycle Oxidative Phosphorylation Glycolysis Krebs Cycle ETC Oxidative Phosphorylation Cell Cytoplasm Mitochondrial Matrix MitoChondrial Matrix Mitochondrial Matrix Inner Membrane Cell Cytoplasm Mitochondrial Matrix Inner Membrane Extension Questions 17. Substrate level phosphorylation is the term used for phosphorylation that removes a phosphate from one molecule and joins it to another molecule. Oxidative phosphorylation is the term used for the attachment of free inorganic phosphate to a molecule. Identify the phases of cellular respiration that use substrate level phosphorylation and that use oxidative phosphorylation. 18. Which side of the inner mitochondrial membrane would have a higher pH? 19. During glycolysis the enzyme hexokinase uses ATP to transfer a phosphate to glucose to form fructose-diphosphate. Suppose that a cell has only glucose available for energy and that the activity of hexokinase is suddenly stopped. Explain in detail what is most likely to occur in the cell. 20. Prokaryote cells must have energy for cellular processes just like eukaryote cells do. Yet, they have no mitochondria. a. Which phase(s) of cellular respiration would be unaffected by the lack of mitochondria in a cell? b. The link reaction and Krebs cycle occur in the cytoplasm of prokaryotes in the same way that they occur in the mitochondria of eukaryotes. However, a concentration gradient across a membrane is a requirement of the electron transport chain. Propose an alternate site for this phase of cellular respiration in prokaryotic cells.