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42 Cards in this Set
- Front
- Back
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Explain the fates of pyruvate under anaerobic conditions.
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Fermentation.
1. pyruvate ----> lactate when this happens it uses up NAD+ so glycolysis cant happen. If you continue making lactate, tissue get acidfied. 2. Pyruvate can be decarboxylated to make acetaldehyde. the acetaldehyde can then be reduced to ethanol. |
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Explain role of thiamine pyrophospate (TPP)
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coenzyme derived from B1.
It is a carrier of active acetoaldehyde groups. |
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TPP dependent Reactions
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1. ethanol fermentation using pyruvate dehydrogenase
2. synthesis of acetyl CoA by using pyruvate dehydrogenase 3. Citric acid cycle by using enzyme alpha detoglutarate dehydrogenase 4. carbon rxns, pentose phosphate pathway. using enzyme transdetolase |
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B1 defiency
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Beriberi
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In what tissues in glucose sole source of energy?
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CNC
erythrocytes testes renal medulaa |
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Describe relationship between two opposing pathways: glycolysis and gluconeogenesis
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glycolysis is breaking down the glucose while gluconeogenisis is making glucose, but they are NOT reverese rxns. Why? b/c glycolysis has 3 irreversible steps with -G, therefore gluconeogenisis must be unique and make glucose from pyruvate
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Describe three steps unique in gluconeogenesis
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they are bypass rxns
Bypass 1: occurs in mitochondria. pyruvate -> oxaloacetate -> PEP. needs pyruvate carboxylase w/biotin and PEP carboxykinase. requires 2 ATP Bypass 2: F 1,6-BP -> F 6-P this is in the cytoplasm Bypass 3: G 6-P -> glucose this is in the cytoplasm |
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Explain why and how glycolysis and gluconeogenesis are reciprocally regulated
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so we dont have a futile cycle. one is usually activated while the other is inactivated. PFK-1 regulation allows this to happen
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How is PFK-1 regulated to cause activation or inactivation of glycolysis/Krebs?
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inactivation of PFK-1 occurs by ATP or Citrate binding to the allosteric site. If these two molecules are hi we dont need to make more so we block pathway.
AMP,ADP, and F 2,6-BP bind to PFK-1 active site. F 2,6-BP stores lots of glucose so it needs to be processed. AMP means ATP is lo so need to make more therefore want glycolyis |
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what is needed to go from fructose 1,6 biphosphate to fructose 6-phosphate for gluconeogenisis?
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enzyme fructose biphosphatase-1
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How is AMP and fructose 2,6 biphosphate potent regulators of glycolysis and gluconeogensis?
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bc both AMP and F26BP activate PFK-1 and inhibit FBPase-1 so glycolysis can occur and gluconeogensis will be inhibited. with the presences of AMP and F26BP it means lots of glucose is present and lo energy so glycolysis is needed to break down glucose and make ATP
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hi F26BP?
lo F26Bp? |
with hi F26BP it will increase PFK-2 and inhibit FBP-2 to increase glycolysis
with lo F26BP it will activate FBPase-2 and inhibit PFK-2 to increase gluconeogensis. |
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Two brances of pentose phosphate pathway
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1. nonoxidative phase
2. oxidative phase |
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describe the nonoxidative phase of pentose phosphate pathway
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it interconverts carbon skelton. the rxn is catalyzed by transketolase and transaldolase. it is an interconversion of 5C to 6C
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describe the oxidative phase of pentose phosphate pathway
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Undergoes oxidative decarboxylation so C6->C5.
Produces NADPH, CO2, and ribose. NADPH is required for the biosynthetic pathway |
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What conenzyme does the transketolase and tranaldolase of pentose phosphate pathway require?
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TPP
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What is role of NADPH in partitioning glucose 6-phos. between glycolysis and pentose phosphate pathway?
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A large amount of NADPH produces during PPP causes inhibition and PPP is shut down. when PPP shuts down then G 6-P can flow into glycolysis
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Describe breakdown of glycogen
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need glycogen phosphorylase and free Phosphate as substrate, this causes release of glucose1-phosphate
This occurs at nonreducing end. problem is that glycogen is branched so debranching enzyme has to move 3 glucose units to end. the G 1-P had to become G 6-P. |
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Describe the synthesis of glycogen
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need glycogen synthase. UDP-glucose adds glucose to the nonreducing end. Need glycogen branching enzyme so glycogen will be branched.
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Why does glycogen degradation and synthesis need to be reversible?
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BC if not neither can functin. If you need glucose synthesize it, if you dont need it, store it as glycogen
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Why is glycogen branched?
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not a long single chain it is branched bc that allows cleavage to be more effient and it allows glycogen to be compact
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Why would gycogen look like wo branching enzyme
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it would be elongated
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factors that determine enzyme activity
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1. association with regulatory protein
2. sequestration of enzyme 3. allosteric regulation 4. covalent modification 5. regulation of transcription and translation |
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example of enzme covalent modification
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phosphorylation
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What regulates glycogen phosphorylas and glycagon synthase?
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protein phosphorylation. a complex chain of signaling allows phosphorylation of glycogen synthase to be in an inactive form.
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explain the coordinated regulation of glycogen synthesis and breakdown
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regulation of glycogen maetabolsim is through the two more hormone insulin and glucagon. With hi blood glucose, insulin increases and insulin dephosphorylates glycogen synthase to activate it. this causes more glycogen to be made to decrease glucose in the blood.
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Explain how allosteric hormonal signals coordinate carbogydrate metabolism
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the hormones insulin and glucagon lower and raise blood glucose liver, all the kinases are allosteric regulators. Phosphorylase kinase with increases glycogen catabolism, or insulin sensitive portein kinase wich dreases glycogen brekdown
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when insulin increases during hi blood glucose what carries glucose to glycogen?
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GLUT 2
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What three things occur with hi blood glucose?
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decrease glycogen breakdown
increase glycogen synthesis increase glycolysis |
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What three things occur with lo blood glucose
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increase glycogen breakdown
decrease glycogen synthesis decrease glycolysis |
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What is the difference in the regulation of carbohydrate metabolsim in liver and in muscle?
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in liver glucagon is the hormone. causing glycogen to be broken down. the same time the glycogen is broken down into glucose, gluconeogenesis is increases and glycolisis is decreases bc the liver wants to share its glucose
The muscle uses norepi which which also increses glycogen breakdown but it also increases glycolysis and decreases gluconeogenesis |
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With lo blood glucose, why is glycolysis increaesed in muscle but decreases in the liver?
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glycolysis pushes hard in muscle bc need ATP wo O2 but the liver inhibits glycolysis bc the glucose is transported to the muscle
BOTH INCREASE BLOOD GLUCOSE |
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Tom Runs 100 m at v. hi speed and muscles become anaerobic so krebs cant occur and the pyruvate becomes lactate. Ouch! what helps him?
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the liver. the lactate is sent to the liver and gluconeogenisis occurs
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Explain three types of metabolic pathways
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1. catabolism
2. diverging anabolism 3. cyclic pathway |
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Explain the additive nature of standard free eneergy change (G)
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The standard free energy change between initial state and final state is directly related to equilibrium. constant.
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What happens to G as Keq gets larger?
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G gets smaller, more negative
so with more product the reaction will go forward |
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Explain how the large and negtive free energy change for ATP hydrolysis serves as a source of energy in many biological phenomena
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The free energy change for ATP hydrolsysi is large and negative so pushes rxn forward. Phosphate has diff ionizaion states so the can be stabilized and have large -G
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Explain the standard reduction potential and the half reactions of oxidation reduction
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Relationship between G and E is reversed. If E is + then G is -. so when E is + rxn goes forward bc it means that G is -. their relationship is porportional but opposite
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If Large Keq, what is G?
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Very Big negative
due to stabilizing effect of isomer |
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describe the coenzymes NADH and NADPH as universal e- carriers
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they are cofactors that are e- and proton carriers to allow oxidation reduction rxns
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Only time glycolysis and gluconeogenisis occur simultaneousy
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during substrate cycle to produce heat
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2 parts of debranching enzyme needed for glycogen breakdown
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transferase to move the chain and gucosidase to pick off one glucose of the chain
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