Biochemistry_Exam_2_Study_Guide[1]

Biochemistry_Exam_2_Study_Guide[1] - Biochem Exam 2 study...

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Biochem Exam 2 study ?’s Gluconeogenesis (* were noted in final review) 1. What steps in the glycolysis pathway cannot be reversed for use in gluconeogenesis?* Phosphorylation of pyruvate to yield phosphoenol pyruvate Dephosphorylation of Fructose-1,6-bisphosphate to F-6-P (the committed step) Dephosphorylation of glucose-6-phosphate to glucose 2. What two types of approaches are used to get around barriers encountered in reversing the glycolytic pathway?* Some reactions take place not only in the cytosol but also in the mitochondria and ER Some enzymes specific to the gluconeogenesis pathway are used. 3. What subcellular organelles are involved in gluconeogenesis? Cytosol, mitochondria, ER 4. What is the malate shuttle , and where does it take place?* Since oxaloacetate cannot diffuse out of the mitochondria, and there is no transporter to mediate its exit, it must be converted to malate by malate dehydrogenase in the presence of NADH . This enzyme is in both the cytoplasm and the mitochondria and this reaction is in equilibrium. Malate can be transported across the mitochondrial membrane. This shuttle also serves to transfer NADH reducing equivalents from mitochondria to the cytosol, since it uses up mitochondrial NADH and produces cystolic NADH.
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5. How does glucose-6-phosphate get converted to glucose? Note: * G-6-P cannot leave the cell, and it is not dephosphorylated in the cytosol. Specifically in the liver, kidney, and intestine, the ER has the capability to carry out the dephosphorylation of G-6-P. G-6-P is transported into the ER by a translocase (T1) where it is dephosphorylated by a phosphatase on the luminal wall of the ER Another translocase (T2) allows the [Pi] to equilibrate b/w the cytosol and E.R. lumen. A third translocase (T3) allows glucose to cross the E.R. membrane and enter the cytosol. Note: *This G-6-phosphatase is also known as phosphohydrolase transphosphorylase and requires Mg for this reaction, and can also catalyze other reactions. 6. Which enzyme used in gluconeogenesis is both inside mitochondria and outside in the cytosol? Malate dehydrogenase 7. What tissues are capable of carrying out all steps of gluconeogenesis? Liver and kidney *In summary, in order to overcome the barriers to reversing glycolysis: 1. Pyruvate went into mitochondria, underwent reactions and malate came out into the cytosol 2. A gluconeogenic enzyme, phosphoenol pyruvate carboxykinase converted oxaloacetate to phosphoenol pyruvate. 3. *A gluconeogenic enzyme, F-1,6-bisphosphatase , dephosphorylated F-1,6-BP to give F-6-BP.* 4. *G-6-P went into endoplasmic reticulum , was dephosphorylated, and glucose came out into the cytosol.*
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Biochem Exam 2 study ?’s Citric Acid Cycle and Oxidative Phosphorylation 1. Why is the citric acid cycle said to be amphibolic? It serves both catabolic (degradative) and anabolic (synthetic) roles 2. What are its catabolic functions? Anabolic? What are other names for the
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This note was uploaded on 05/02/2010 for the course BIO 1 taught by Professor Tate during the Spring '10 term at Nova Southeastern University.

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Biochemistry_Exam_2_Study_Guide[1] - Biochem Exam 2 study...

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