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* This process happen in the inner membrane of mitochondria H6C12O6 Dehydrogenase H H 2e NAD+ + H + H + 2e Reduction O NADH O The cellular respiration requires through 3 stages : 1. Glycolysis: Converts Glucose to Pyruvate. 2. Krebs Cycle: Completes the oxidation of organic molecules. 3. Electron Transport: chain to synthesis ATP. Cellular Respiration generates 38 ATP for each sugar molecule. By substrate-level phosphorylation By Oxidative phosphorylation By substrate-level phosphorylation 1. 2. It occurs in the cytoplasm with the absence of O2 During this stage the Glucose will split into 2 molecules. By oxidizing these 2 molecules they form 2 molecules of Pyruvate. Each step in this stage is catalyzed by a specific enzyme The steps are divided to 2 phases: Energy investment phase ( requires 2 ATP ) by Phosphorylation Energy payoff phase ( produces ATP ) by substratelevel phosphorylation and NAD is reduced to NADH Thus, Glycolysis produces 2 ATP and 2 NADH and 2 Pyruvate molecules per glucose. The terminal phosphate changes the shape of the molecule to work. When Transport e.g. membrane protein the phosphate group leaves the molecule, the molecule returns to its alternate shape. Chemical e.g. forming products from reactants. • An animal cell regenerates ATP from ADP Mechanical e.g. motor protein and Pi by the catabolism of organic molecules. • The transfer of the terminal phosphate group from ATP to another molecule is phosphorylation These reactions release energy when electrons move closer to electronegativity atoms like Oxygen. They require both donor and receptor. The loss of electrons. Done by reducting agent The addition of electrons. Done by oxidizing agent Na + Cl Na+ + Cl- Here sodium is oxidized and chlorine is reduced . the electron donor, is the reducing agent while the electron recipient, is the oxidizing agent. No CO2 is produced ( in the absence of O2) Energy investment phase ADP ATP ATP + + Glucose ADP 2 pyruvates Energy payoff phase ADP 4P ADP ADP ATP ATP ATP ATP ADP NAD+ NAD+ reduction NADH NADH Net yield: 2 Pyruvates 2 NADH 2 ATP It occurs mainly in the mitochondrial matrix and includes 2 cycles: 1. PRE-Krebs cycle: The Pyruvate molecule is converted to Acetyl-coA in the presence of the Oxygen. 2. Krebs cycle: Each pyruvate molecule provides 1 ATP by substrate-level phosphorylation 3 NADH and 1 FADH2 Thus, the outcome from 2 pyruvate molecules would be: 2 ATP 6 NADH 2 FADH2 + 1 CO2 Oxidized ee- + 2 CoA 3 CO2 NAD+ NADH NAD+ NADH Acetyl-CoA Acetyl-CoA Acetyl-CoA 1 Acetyl-CoA 2 Citrat e + Citrat e 4C 4C 2CO2 Citrat e 6 2 NADH FADH2 ATP ATP Citrat e The majority of the ATP come from the energy in the electrons NADH and FADH2 these electrons power the ATP synthesis. These chains of electron transport are found in the surface of the cristae in the inner membrane of the mitochondria. What happens to the electrons from NADH and FADH ? They are ultimately passed to Oxygen to form water. 1 6 NADH 2 FADH2 Net yield: 34 ATP Electron Transport Chain 2 3 H H + + H H ADP + + Chemiosmosis ATPSynthase +P H ATP Intermembrane space Inner membrane H Matrix + + H H + + Glycolysis + Krebs cycle + oxidative phosphorylation 2 ATP + 2 ATP + 34 ATP = 38 ATP Glycolysis By substrate-level phosphorylation •Happens in the cytoplasm •Net yield: 2 pyruvates, 2 NADH & 2 ATP Krebs Cycle By substrate-level phosphorylation •Happens in the matrix •Net yield: 6 NADH, 2 FADH2 & 2 ATP Electron transport By Oxidative Phosphorylation •Happens in the inner membrane of the mitochondria •Net yield: 34 ATP 38 ATP complete degradation needs O2 Food+O2 Partial degradation Doesn’t need O2 H2O + CO2 + Energy heat work Less energy Rich in energy Organic molecules Degradation (by enzymes) simpler molecules • In alcohol fermentation, pyruvate is converted to ethanol in two steps. – First, pyruvate is converted to a two-carbon compound, acetaldehyde by the removal of CO2. – Second, acetaldehyde is reduced by NADH to ethanol. – Alcohol fermentation by yeast is used in brewing and winemaking. • During lactic acid fermentation, pyruvate is reduced directly by NADH to form lactate (ionized form of lactic acid). – Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt. – Muscle cells switch from aerobic respiration to lactic acid fermentation to generate ATP when O2 is scarce. • The waste product, lactate, may cause muscle fatigue, but it is converted back to pyruvate in the liver. Play video Cellular Respiration (Electron Transport Chain) http://www.youtube.com/watch?v=xbJ0nbzt5Kw Electron Transport Chain Animation Overview Chemiosmosis HQ http://www.youtube.com/watch?v=kN5MtqAB_Yc PLZ OPEN THE VIDEO Oxidative Phosphorylation http://www.youtube.com/watch?v=ajZajFrCjtA Play video Q1: Write whether each of the following statements is True (T) or False (F): 1-Accumalation of lactic acid in human is due to alcohol fermentation. 2-Glycolysis is a catabolic process that occurs in the mitochondria,however Krebs cycle occurs in the cytoplasm. 3-Cytochromes are proteins that function as electron carriers in the mitochondria. 4-the net yield of ATP by substrate level phosphorylation during citric acid cycle for each glucose molecule is two. 5- FADH2 is an electron carrier in glycolysis. 6- When O2 is scarce (very few), human muscles produce ATP by lactic acid fermentation. 7- Carbohydrates are the only fuel used to produce ATP by cellular respiration. Q 2: Choose the correct answer (one answer only): Which molecule is one of the ATP constituents; a-Adenosine. b-Cholesterol. c-The amino acid Tryptophan. 2-During formation of Acetyl CoA;- a-2NADH molecules are produced. b-3NADH molecules are produced. c-2ATP molecules are produced. 3-Which process in eukaryotic cell will normally proceed whether O2 is present or absent;- a-Glycolysis. b-kreb cycle. c-Electron transport system. 4-Complete oxidation of one molecule of glucose will produce ------molecules of ATP;- a-32. b-34. c-38. 5-No ATP produced by substrate level phosphorylation during ;- a-Glycolysis. b-Citric acid cycle. 6-Cellular respiration is a catabolic process that transfers hydrogen from;- a-Sugar to water. b-Sugar to oxygen. c-Oxygen to sugar. 7- The oxidizing agent of glycolysis is: a- NAD+. b- O2 . c- NADH. d-FADH2. 8- Chemiosmosis is the process of generating ATP at: a- The inner membrane of mitochondria. b- Mitochondrial matrix. c- The outer membrane of mitochondria. d-Cell cytoplasm. 9- Each NADH, that transfers H from food to the electron transport chain generates: a- 2 ATP . b- 3 ATP. c- 4 ATP. 10- Which of the following compounds is considered as the fuel of the Krebs cycle? a) - acetyl coA