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Download Glycolysis is the first stage of cellular respiration
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Name: ________________________________ The following information on cellular respiration is not all accurate I want you to read it and correct the mistakes. Anything in italics is correct and does not need to be corrected. There are approximately 60 mistakes that need to be fixed. We eat a potato which is full of the polysaccharide glycogen which is digested by salivary amylase. The polysaccaride is broken down to monosaccarides glucose which are absorbed into the blood through the wall of the small intestine. As the blood glucose level rises the hormone glucagon is released by the alpha cells of the pancreas which bind to receptor lipids on numerous target cells initiating the uptake of glucose by those cells from the blood. The movement of glucose into a cell is a type of passive transport. The digested glucose molecules move into the cytoplasm where the four stages of cellular respiration digest them further into water, ATP and oxygen. Glycolysis is the first stage of cellular respiration: In the cytoplasm a series of enzymatic reactions act on glucose breaking it down to four pyruvate molecules, generating a net gain of 4 ATP, and 2 NADH. (Note: the enzymes responsible for glycolysis are produced by free ribosomes in the cytoplasm). The four ATP molecules produced in glycolysis are made by the process of chemiosmosis. The enzymes responsible for converting ADP to ATP during the process of glycolysis are generally referred to as dehydrogenases. The production/conversion of NAD+ to NADH is the result of redox reactions usually catalized by kinase enzymes. The glucose molecule is being reduced and the NAD+ molecule is being oxidized. Thus, the reducing agent NAD+ loses energy/electrons while the oxidizing agent glucose gains energy/electrons. The breakdown of a mole of glucose is a nonspontaneous reaction and the cell must invest 2870kj of energy to overcome the EA. During the first few steps of glycolysis the glucose molecule is phosphorlyated by endergonic/anabolic hydrolysis of ATP. The phosphorlated intermediate is more reactive and more likely to breakdown. Before the 2 pyruvate molecules from glycolysis are able to enter the Krebs cycle which is a group of enzymes located in the cistae of the mitochondria, they are converted to Acetyl ACO. During the conversion of pyruvate to Aceytl ACO a CO2 and FADH2 molecule are produced. The Krebs cycle the second stage of cellular respiration: a series of reactions catalyzed by enzymes located in the mitochondria matrix (remember the mitochondria has it’s own DNA, therefore it is able to produce its own enzymes). The final products of the Krebs cycle: 6NADH, 4FADH2, 4ATP & 6CO2. The ATP molecules from the Krebs cycle can be used directly to provide 8 kcal/mol of energy for both endergonic and exergonic reactions. The CO2 diffuses out of the mitochondria, then out of the cell, where it binds to red blood cells and is carried to the lungs and inhaled. The 2NADH from glycolysis, 6NADH & 2FADH2 from the Krebs cycle, and 2NADH from the conversion of pyruvate to Acetyal COA move to the outer membrane of the mitochondria where the ETC is located. The ETC the third stage of cellular respiration: it is a series of lipids found in the outer mitochondrial membrane. The protons are passed from the electron carriers/coenzymes NAD+ and FADH to the cytochromes. A series of Redox reactions occur as the protons are passed down the lipid chain. The energy being released from the redox reactions is used to produce an electron gradient in the outer membrane space. At the end of the ETC a hydrogen acts as the final proton acceptor forming water. Why do these reactions take place the oxygen at the end of the ETC is the driving force, its attraction (high electronegativity) for electrons pulls all the other reactions forward. The concentration of protons in the inner membrane space creates a proton gradient. Energy from the gradient is used to produce ATP. The protons want to diffuse back into the mitochondrial matrix the only way to get through the inner membrane is through ADP synthase. As the protons move through the ADP synthase ATP is converted to ADP. Substrate level phosphroylation is the process of producing ATP in the ETC. For each NADH molecule that drops off electrons four protons are pumped into the inner membrane space resulting in the production of three ATP molecules. For every FADH2 molecule that drops off electrons one proton is pumped into the inner membrane space resulting in the production of one ATP. Total production of ATP in cellular respiration: Glycolysis: Produces 2 ATP directly 2NADH ------------------> 6 ATP Krebs: Produces 4 ATP directly 6 NADH ------------------> 24 ATP 2 FADH2 -----------------> 4 ATP Plus: 2 Pyruvate ---------------- Acetyal COA Produces 2 NADH ------------------------------- 6 ATP Total Production: 40 ATP