METAB 1 EXAM 2 STUDY GUIDE SUMMER 2013 TCA Cycle Krebs Cycle Citric Acid Cycle a Know various names for this cycle b Recognize and be able to give examples of this cycle s role as a common metabolic pathway e g where can its intermediaries originate What can they be diverted from the cycle and used for they re ketogenic can form ketone bodies that can be oxidized to make acetyl CoA acetyl CoA are broken down into fatty acids which can then undergo beta oxidation to form are cleaved into AAs which can then be transaminated to form pyruvate OR if are metabolized as glucose which goes through glycolysis to form pyruvate d Carbohydrates e Lipids c Proteins f Citrate can be used in the synthesis of fatty acids g Alpha ketoglutarate can be used to synthesize glutamate through transamination h Succinyl CoA can be part of the heme portion of some molecules i OAA can be transaminated into aspartate and then used to form pyrimidines j OAA can also be converted into glucose k Know reactions enzymes energetics etc l Molecules Mnemonic Citrate Can cis Aconitate intermediate Adam Isocitrate Intrigue alpha Ketoglutarate A Succinyl CoA Succinate Fumarate Malate Oxaloacetate OAA Super Sexy Foxy Mama Okay Enzymes Mnemonic Coenzymes Energetics citrate Synthase gives off CoASH So At dehydration H2O Another hydration H2O Aconitase Aconitase isocitrate Dehydrogenase Dance NAD gives off CO2 NADH H 3 ATPs ketoglutarate Dehydr ogenase complex Devon like PDH complex TPP FAD NAD CoASH lipoate gives off CO2 NADH H 3 ATPs succinic Thiokinase Took GDP gives off CoASH GTP 1 ATP used to convert OAA PEP in gluconeogenesis succinate Dehydrogenase Down FAD FADH2 2 ATPs Fumarase Five hydration H2O Enzymes Mnemonic Coenzymes Energetics malate Dehydrogenase Drinks NAD NADH H 3 ATPs TOTAL 12 ATPs molecule of Acetyl CoA RED rate controlling enzymes YELLOW ATP formation Liver kidneys cardiac muscle produce 38 ATPs because they have the malate shuttle that uses the NADH H to form NAD 3 ATPs formed Skeletal muscle and brain produce 36 ATPs because they use the glycerol 3 phosphate shuttle that uses FAD to form FADH only 2 ATPs formed m Identify example of substrate level phosphorylation n Succinyl CoA Succinate o enzyme succinic thiokinase p kinase high energy compound production of ATP GTP ATP q in this case uses GDP GTP r Describe the role of OAA in regulating cycle activity s Discuss the role of NADH and ATP in controlling TCA cycle activities t End product inhibition u NADH H inhibits all dehydrogenases because they are the by products v ATP inhibits citrate synthase first step in cycle because we don t need to generate reduced coenzymes to be sent to the ETC to make more ATP and isocitrate dehydrogenase ONLY ONE w Citrate blocks citrate synthase because citrate is already formed x Succinyl CoA inhibits alpha ketoglutarate dehydrogenase enzyme prior because it is already formed and citrate synthase y z Electron transport chain ETC a State the purpose and cellular location and list the components of the ETC Purpose to form ATP energy by coupling the processes of oxidation and phosphorylation The coenzymes previously reduced in the TCA cycle etc are being re oxidized and ADP is being phosphorylated to ATP Cellular Location inner mitochondrial membrane TCA Cycle happens in the matrix Components 4 proton pump complexes embedded in the membrane I NADH dehydrogenase complex pumps 4 protons where NADH H starts II Succinate Q reductase does NOT pump any protons where FADH2 starts III Cytochrome B C complex pumps 4 protons IV Cytochrome oxidase complex pumps 2 protons ONLY because 2 are going to be used to form water by reducing 1 2 O2 ATP Synthase complex V F0 allows for the translocation of protons rotates and changes conformation of the complex to allow for phosphorylation of ADP F1 catalytic part that contains binding sites for ADP and inorganic phosphate 2 mobile electron transporter complexes Ubiquinone coenzyme Q transports pairs of electrons between complex I to III or II to III Cytochrome C transports pairs of electrons between III and IV b Discuss how ATP is synthesized via oxidative phosphorylation The pumping of protons 4 for every pair of electrons from NADH H and FADH2 out into the intermembrane space of the mitochondria causes an energy gradient This gradient allows for the passive diffusion of protons back out through the ATP synthase complex into the matrix F0 starts rotating and allows the protons to flow back in through F1 by changing the conformation of the complex This return flow of protons furnishes the energy necessary for the synthesis of ATP from ADP and inorganic phosphate in the matrix and is catalyzed in the F1 part of the enzyme c State why the maximum theoretical yield of ATPs for electrons introduced into the ETC via NADH H is 3 whereas for electrons introduced via FADH2 is 2 When you start the ETC with 2 NADH H you start at complex I and pump a total of 10 protons H out When you start the ETC with 2 FADH2 you start at complex II and only pump a total of 6 protons H out Therefore the energy gradient will be larger when using NADH H and will produce more ATP due to more protons being brought back in through ATP synthase Fructose and galactose metabolism a Why are fructose and galactose metabolized primarily in the liver Hexokinase can phosphorylate any hexose and is present in all cells in the body including the liver but it is rare for it to phosphorylate fructose galactose because hexokinase is saturated at all times with glucose has a lower Km for glucose therefore higher affinity Hexokinase has a higher Km lower affinity for fructose and galactose when compared to glucose Therefore the liver has specific enzymes fructokinase and galactokinase to phosphorylate fructose and galactose at the start of their metabolism b Discuss how ingestion of large amounts of fructose may have detrimental metabolic consequences Fructose enters glycolysis as a triose phosphate glyceraldehyde 3 phosphate AFTER the rate controlling step that includes PFK 1 Therefore if we ingest fructose there is no rate control of its conversion to pyruvate This pyruvate can be converted to acetyl CoA which then increases the synthesis of FA in the liver and then these FA can be incorporated into triglycerides DHAP can also be converted to glycerol 3 phosphate by glycerol 3 phosphate dehydrogenase and glycerol 3 phosphate is the backbone of triglycerides These triglycerides are then transported from the liver to other tissues
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