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BioChem Exam 3
| Question | Answer |
|---|---|
| Describe the influx of metabolites for gluconeogenesis | Oxaloacetate (Glucogenic Amino Acids) |
| List the sites of glycogen synthesis and degradation | Liver and muscle |
| Describe the structure of glycogen | Composed of monomers of glucose-1-phosphate made through an isomerization reaction |
| The pathway of glycogen synthesis | Synthesis in the liver and muscle (Glucose->Glucose 6-P->Glucose 1-P->IDP-Glucose->Glycogen) |
| Describe the reaction catalyzed by the unique enzymes in the synthesis pathway | Hydrolysis of inorganic pyrophosphate drives the reaction, Glycogen synthase needs a glycogen primer called glycogenin |
| Describe the substrates and products of Pentose phosphate pathway | (NADPH->Reductive biosynthesis) (Fructose 6-phosphate Glyceraldehyde 3-phosphate->Glycolysis/Gluconeogenesis) (Ribose 5-phosphate->Nucleic acid synthesis) |
| Identify the oxidative reactions | (Irreversible) (Glucose-6-phosphate->NADP+/glucose-6-phosphate dehydrogenase->6-Phosphoglucono-lactone->hydrolysis->6-phosphogluconate (6-Phosphogluconate->6-phosphogluconate dehydrogenase->Ribulose-5-phosphate) |
| Explain the effect of glucose-6-phosphate dehydrogenase deficiency | Causes hemolytic anemia |
| What are the two enzymes required to convert pyruvate to phosphoenolpyruate in the two steps of gluconeogenesis | Pyruvate carboxylase and Phosphoenolpyruvate carboxylkinase |
| When glucagon binds to its receptors in what state is the fructose bisphosphatase-2 (half. of the bifunctional enzyme) | Phosphorylated and active |
| Identify the non-oxidative reactions | (Reversible) Set of interconversions that produce 3,4,5,6, and 7 carbon sugars using Transketolases/Transaldolases (forms GAP, Ribose 5-P, Fructose. 6-P) |
| How many ATPs are used in gluconeogenesis | 6 |
| The pathway of glycogen degradation | Degradation in the liver (Glycogen->Glucose 6-P->Glucose->Blood Glucose) Degradation in the muscle (Glycogen->Glucose->Glucose 6-P->Glycolysis->ATP) |
| Describe the reaction catalyzed by the unique enzymes in the degradation pathways | Linear chains are broken down via phosphorolysis (Glycogen->glycogen phosphorolysis->Glucose-1-phosphate->phosphogluco-mutase->Glucose-6-phosphate->glucose-6-phosphatase->Glucose), Branched chains of glycogen are broken down via hydrolysis (alpha-1-6-glycosidic bond cleaved) |
| Where do glycogenesis and glycogenolysis occur | Liver and muscle |
| The hydrolysis of ___ drives the reaction from glucose-1-phosphate to UDP-glucose | pyrophosphate |
| Cleaves off a seven-residue segment and reattaches it to a glucose C6-OH to create an alpha(1->6) branch point | Transglycosylase (branching enzyme) |
| What lacks glucose-6 phosphatase and can enter glycolysis at Step 2 (1 less ATP is consumed so net gain is higher) | The muscles |
| Glycogen alpha(1-6) glycosidic bonds are cleaved by | Debranching enzyme |
| Describe how glycogen synthesis and degradation are regulated by glucagon | Glucagon phosphorylates glycogen synthase (inactivating it) and glycogen phosphorylase (activating it) |
| Describe how glycogen synthesis and degradation are regulated by insulin | Insulin dephosphorylates glycogen synthase (activating it) and glycogen phosphorylase (inactivating it) |
| When insulin binds to its receptor, glycogen synthase will be ___ | Active |
| This enzyme converts 6-phosphogluconate to ribulose-5-phosphate | 6-phosphogluconate dehydrogenase |
| The oxidative reactions of the pentose phosphate pathway produce | NADPH |
| Net reaction for the pentose phosphate pathway | Ribose derivative is produced, 2 NADPH molecules are formed |
| Synthesis of glucose from non-carbohydrate precursors (amino acids, lactate, glycerol) in the liver, during fasting state, and is the reverse of glycolysis | Gluconeogenesis |
| During glycogen synthesis, glucose-1-phosphate is activated to ___ prior to adding to a growing chain of glycogen | UDP-glucose |
| Describe the reaction that converts pyruvate to acetyl CoA | The pyruvate dehydrogenase complex includes three types of enzymes that collectively remove a carboxylate group from pyruvate and produce acetyl CoA and NADH |
| Describe the steps of citric acid cycle with emphasis on: Rxns that are regulated | Rxn 1: Citrate synthase adds an acetyl group to oxaloacetate, Rxn 3: Isocitrate dehydrogenase releases the first CO2, Rxn 4: alpha-Ketoglutarate dehydrogenase releases the second CO2 |
| The enzyme needed to initiate a 10 molecule primer to begin glycogen synthesis is | glycogenin |
| Describe the steps of citric acid cycle with emphasis on: Substrate level phosphorylation | Rxn 5: Succinyl-CoA synthetase catalyzes substrate level phosphorylation |
| Describe the total energy output from TCA cycle (starting from glycolysis) | 32 ATP |
| Describe the substrates that flow in and out of citric acid cycle | Amino acids, Odd chain fatty acids, Pyruvate, Precursors for (Glucose, Pyruvate, Fatty acids and cholesterol, AAs, Nucleotides, Heme) |
| When glucagon is released you would expect ___ | glycogen synthase to be inactive |
| Which pyruvate dehydrogenase subunit is responsible for transferring the acetyl group to CoA, to form acetyl CoA | E2 |
| Pyruvate dehydrogenase is activated when it is ___ | Dephosphorylated |
| This enzyme converts isocitrate into alpha-ketoglutarate | Isocitrate dehydrogenase |
| This amino acid is responsible for accepting a phosphate from succinyl phosphate before transferring to GDP as part of the succinyl-CoA synthetase reaction | Histidine |
| The three irreversible steps of citric cycle | 1. Citrate synthase 2. Isocitrate dehydrogenase 3. alpha-Ketoglutarate dehydrogenase |
| What molecule or cofactor can inhibit all three regulated steps in the citric acid cycle | NADH |
| Type of reaction if amino acids, odd chain fatty acids, or pyruvate flow into citric acid cycle | Anaplerotic reactions |
| This enzyme catalyzes the regeneration of oxaloacetate | Malate dehydrogenase |
| These intermediates can flow into the citric acid cycle in anaplerotic reactions by forming alpha-Ketoglutarate | Amino Acids |
| Intermediates that flow in and out of Citric Acid Cycle | IN: Amino Acids (alpha-Ketoglutarate, Fumarate, Oxaloacetate, Succinyl-CoA), Odd chain fatty acids (Succinyl-CoA), Pyruvate (Oxaloacetate) OUT: Glucose (Oxaloacetate), Fatty acids and cholesterol (Citrate), Amino Acids (alpha-Ketoglutarate), Nucleotides (alpha-Ketoglutarate), Heme (Succinyl-CoA), Pyruvate (Malate) |
| What activates pyruvate dehydrogenase to make acetyl CoA | Ca2+ |
| When muscles contract they release Ca2+ ions that can activate the following enzymes | Isocitrate dehydrogenase and alpha-Ketoglutarate dehydrogenase |
| This enzyme removes a carboxylate from pyruvate and adds the acetyl group to CoA | Pyruvate dehydrogenase |
| Summarize the thermodynamics of oxidation-reduction reaction | One reactant is in its oxidized state while the other is in its reduced state, the greater the reduction potential the greater the tendency of a substance to accept electrons and be reduced |
| Map the path of electrons through the redox groups of the electron transport pathway | NADH->NAD+->Complex I->Q->Complex III->Cytochrome C->Complex IV->O2->H2O |
| Explain how the protonmotive force links electron transport and ATP synthesis | Complex V uses the proton gradient to phosphorylate ADP called ATP synthase |
| Describe the structure and operation of ATP synthase | F0 is made up of 8 subunits that each translocate a proton to flow back into the matrix, F1 is made up of 6 subunits and catalyze the rxn of ADP to ATP |
| Indicates a substance's tendency to accept electrons | Reduction potential |
| Transports reducing agents across the inner mitochondrial membrane | Malate-aspartate shuttle |
| In the electron transport chain which ones transport protons | Complex I (4), Complex III (4), Complex IV (2), Complex V (1) |
| The malate-aspartate shuttle transfer ___ | Malate into the matrix and aspartate into the cytosol |
| The imbalance of protons represents a source of free energy that can drive the activity of an ATP synthase | Protonmotive force |
| This protein imports ADP into the matrix and exports ATP into the intermembrane space | ATP translocase |
| When insulin is released after a meal, glycogen synthase is | Activated |
| This molecule is the most potent activator of PFK-1 in glycolysis and is an inhibitor of fructose bisphosphate in gluconeogenesis | Fructose 2,6 bisphosphate |
| When glucagon is present, the fructose bisphosphate-2 half of the bifunctional enzyme is | active |
| When glucagon binds to its receptor, it activates adenlyl cyclase which generates a second messenger which in turn activates various enzymes. What is the second messenger molecule | cAMP |
| Glycogen synthase needs a glycogen primer. The primer is generated by this enzyme | Glycogenin |
| What enzyme is lacking in muscle, allowing glucose-6-phosphate to enter glycolysis at step 2 | Glucose-6-phosphatase |
| What is the product of one round of the citric acid cycle | 3 NADH, 1 QH2, 1 GTP |
| The source of lactate to produce pyruvate are ___ | RBC and muscle |
| What are the two enzymes required to convert pyruvate to phosphoenolpyruvate in the two step process of gluconeogenesis | Pyruvate carboxylase and phosphoenolpyruvate carboxylkinase |
| True or False: Glycogen has no phosphate groups | True |
| Free energy source for glycogen synthesis | UTP |
| In the muscle, when a residue of glucose is cleaved from glycogen and converted to pyruvate via glycolysis, what is the net ATP production | 3 |
| What enzyme is used in both glycogen synthesis and glycogenolysis | Phosphoglucomutase |
| Substrates for glycogen phosphorylase are | Pi and glycogen |
| The substrates for the PPP are | G6P and NADP+ |
| If F2BP is high then ___ | Glycolysis if on and gluconeogenesis is off |
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tm15