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90 Cards in this Set
- Front
- Back
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Rate limiting enzyme in glycolysis
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Phosphofructokinase I
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Substrate for the rate limiting enzyme in glycolysis
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Fructose 6 phosphate
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Committed step in glycolysis
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Fructose 1,6 bisphosphate
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Second key regulatory enyzme in glycolysis
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Pyruvate kinase
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Two fates of pyruvate
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In aerobic conditions, pyruvate is reduced to lactate and in anerobic conditions it is oxidized to acetyl coA
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Crucial enzyme that allows entry of carbon into stage 2 of glycolysis and uses NAD as a cofactor
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Glyceraldehyde 3 phosphate dehydrogenase
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Enzyme that oxidizes NADH to NAD to make lactate
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lactate dehydrogenase
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Enzyme that makes acetyl coA from pyruvate in the mitochondria
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pyruvate dehydrogenase complex
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cofactor that binds pyruvate in teh PDH complex
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TPP--> thyminpyrophosphate
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What is reduced in pyruvate dehydrogenase complex?
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lipoic acid, FAD, NAD
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What provides a source of electrons in the PDH complex?
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NAD to NADH reduction
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What builds up in lactic acidemia which is a defect in pyruvate dehydrogenase complex?
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Lactate and pyruvate
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What is the most common defect in the pyruvate dehydrogenase complex?
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In the alpha subunit of E1 which leads to defective TPP binding. Sometimes thiamine therapy is effective.
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How many carbons are the in the compound that enters the TCA cycle?
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6...called citrate
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What is citrate made from?
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4 carbon oxaloacetate and 2 carbon acetyl coA
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What is the pace maker of the whole TCA cylce called the condensation reaction?
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4C plus 2C to make 6C pyruvate
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What is released from the TCA cycle as the 6 carbon is being decarboxylated back to the 4 carbon?
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3 molecules of NADH, 1 molecule of FADH, 1 GTP, 2 CO2
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What (two things) does the malate aspartate shuttle do?
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1) way to oxidize NADH under aerobic conditions and 2)makes some ATP
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Which two TCA components make amino acids? which one makes fatty acids? which one makes porphyrins?
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1) oxalacetate and alpha ketogluterate
2) citrate 3) succinyl coA |
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What are the two regulatory enzymes of glycolysis and what do the inhibit and stimulate?
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phosphofructokinase I and pyruvate kinase
+ AMP, fructose 1,6 bisphosphate - ATP, citrate |
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What is the regulatory enzyme of pyruvate dehydrogenase? and what does it inhibit?
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pdh kinase
- NADH, acetyl coA, atp |
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What are the regulatory enzymes of TCA cycle (3)?What do they inhibit and stimulate?
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Citrate synthase, isocitrate dehydrogenase, alpha ketoglutarate dehydrogenase
+ AMP, ADP, oxaloacetate -NADH, ATP, succinyl coA |
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Which two enzymes trap glucose inside the cell for glycolysis?
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Hexokinase and glucokinase
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Which enzyme do you use to make the committed step of glycolysis?
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PFK I
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Which enzyme makes the final product of glycolysis?
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Pyruvate kinase
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How do LOW levels of ATP influence PFK I?
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Increase the binding affinity for the substrate fructose 6 phosphate
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How does protein kinase a effect pyruvate kinase?
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It phosphorylates it and makes it inactive
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When levels of NADH, acetyl coA and ATP are high, what happens to PDH kinase?
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The kinase on E1 is activated and phosphorylates E1 which inactivates E1 so it can't bind pyruvate and pyruvate doesnt get converted to acetyl coA
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What do high levels of ATP in the TCA cycle inhibit?
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isocitrate dehydrogenase
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What do high levels of succinate and NADH inhibit in the TCA cycle?
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alpha ketogluterate dehydrogenase
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What is the most common disorder in glycolysis?
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pruvate kinase problems
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What disorder of the rbc do you get in pyruvate kinase deficiency?
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Echinocyte because with low ATP there is trouble maintaining the NaK atpase so you get loss of water from the cell
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Which pathway of the pentose phosphate shunt produces NADPH?
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The oxidative pathway
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What two enzymes in the pentose phosphate shunt use NADP as a cofactor in the oxidative stage?
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Glucose 6 phosphate dehydrogenase and 6 phosphogluconate dehydrogenase
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What is the major rate limiting enzyme of the pentose phosphate shunt?
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glucose 6 phosphate dehydrogenase
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What regulates glucose 6 phosphate dehydrogenase in the pentose phosphate shunt?
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NADPH
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What in the nonoxidative stage of the pentose phosphate shunt has thiamine pyrophosphate as a cofactor?
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Transketolase
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What does ribose 5 phosphate turn into in the pentose phosphate shunt?
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nucleosides and intermediates for glycolysis
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What three compounds drive gluconeogenesis?
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amino acids, lactate, glycerol
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What is the initiation molecule of glycogen synthesis?
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Glycogenin
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Does free glucose have the energetics to serve as a substrate for glycocidic bonds?
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No
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What form does glucose have to be in to serve as substrate for hte formatin of alpha 1,4 glycocytic bonds?
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UDP-glucose
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What is the rate limiting enzyme of glycogen synthesis?
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glycogen synthase
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Which hormone is going to promote glucose uptake and the glycogen synthetic machinery?
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Insulin
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What is the branching enzyme in glycogen synthesis that breaks 1,4 bonds and makes 1,6 branch points?
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amylo 1,4-1,6 transglycosylase
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What is the rate limiting enzyme of glycogenolysis?
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glycogen phosphorylase
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What enzyme takes the phosphate off glucose 6 phosphate to make free glucose?
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glucose 6 phosphatase
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Where is the glucose 6 phosphate enzyme located?
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In the ER
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How do you get the complete action of glycogen phosphorylase?
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Use it with a debranching enzyme
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Which hormone stimulates glycogen phosphorylase?
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Glucagon
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What are 1,4 1,4 glucantransferase and amylo 1,6 glucosidase?
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Debranching enzymes
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Do the enzymes in glycogen synthesis have to be phosphorylated or dephosphorylated to work?
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They are active when they are dephosphorylated and inactive when they are phosphorylated.
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Do the enzymes in glycogenolysis have to be phosphorylated or dephosphorylated to work?
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They are active when they are phosphorylated and inactive when they are dephosphorylated.
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What is made when glucagon binds to its receptor?
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Cyclic AMP
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What does protein kinase A do?
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It phosphorylates and thereby activates phosphorylase kinase which then phosphorylates glycogen phosphorylase and activates it to make free glucose by glycogenolysis
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What happens when insulin binds to its receptor in the well fed state?
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It activates a kinase that phosphorylates protein phosphatase I which will 1) take off the phosphate on glycogen synthase thereby activating and 2) take the phosphates off phosphorylase kinase and glycogen phosphorylase thereby inactiving the enzymes for glycogenolysis
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Which enzyme inhibits glycogenolysis?
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protein phosphatase I
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What three things does protein kinase A do in response to glucagon binding its receptor in the fasting state?
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1) activates glycogenolysis by phosphorylating phosphorylase kinase which then phosphorylates glycogen phosphorylase and with the help of debranching enzymes it breaks down glycogen into free glucose 2) stops glycogen synthesis by phosphorylating glycogen synthase and thereby inactivating it 3) blocks an enzyme that would just reverse all of this work by phosphorylating an inhibitor protein on protein phosphatase I
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What two metabolites does the muscle give to the liver for gluconeogenesis?
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Lactate from glycolysis and amino acids from proteolysis
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Which two organs do gluconeogenesis?
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Liver mainly and then the kidney
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What are the two enzymes in cycle III of regulation in gluconeogenesis?
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PEP carboxykinase and Pyruvate carboxylase
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When pyruvate is converted in oxaloacetate in the mitochondria what is added to pyruvate, what is the enzyme and cofactor and requirement?
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The enzyme is pyruvate carboxylase, CO2 is added, the cofactor is biotin, and this reaction requires ATP
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What is the rate limiting enzyme for gluconeogenesis and what does it do?
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PEP carboxykinase and it takes the CO2 off oxaloacetate then phosphorylates it with GTP to make PEP
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What is the substrate for PEP carboxykinase?
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oxaloactetate
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What is essential for the activation of pyruvate carboxylase?
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Acetyl coA
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By what mechanism is PEP carboxykinase activated?
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A cAMP mechanism such that there is an increase mRNA for the enzyme that encodes PEP carboxykinase when glucagon is high in the fasting state
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What binds, when elevated, to PFK 1 to activate it for the glycolytic route?
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Fructose 2,6 bisphosphate
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What are the two actions of fructose 2,6 bisphosphate?
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It is an activator of PFK1 and a competitive inhibitor of FBPase.
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What happens when fructose 2,6 bisphosphate is elevated?
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Glycolysis goes up and gluconeogenesis goes down
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What happens when fructose 2,6 bisphosphate is depressed?
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Gluconeogenesis goes up and glycolysis goes down
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What happens to fructose 2,6 bisphosphate levels when insulin is around? Which parts of the enzyme are active and inactive?
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Fuctose 2,6 bisphosphate levels are up because the enzyme is in the dephosphorylated state and the kinase is active but the phosphatase is inactive so fructose 6 phosphate is being converted to fructose 2,6 bisphosphate
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What happens to fructose 2,6 bisphosphate levels when glucagon is around? Which parts of the enzyme are active and inactive?
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Fuctose 2,6 bisphosphate levels go down because the enzyme is phosphorylated by protein kinase A from activation by cAMP so now the kinase is inactive and the phosphatase is active so fructose 2,6 bisphosphate will be converted into fuctose 6 phosphate and gluconeogenesis will occur
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Which enzyme makes and breaks down Fructose 2,6 bisphosphate?
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PFK II
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What will the free fatty acids principally be used for?
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oxidation and ketone production
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What will the glycerol molecule be used for?
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gluconeogenesis
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What are the 4 glycolytic enzyme targets in tumors?
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1) Hexokinase inhibtors will hit the first stage of glycolysis
2) blocking HK dissociation from the mitochondria leads to cell death 3) inhibitors of PDH kinase make too much pyruvate for use 4) inhibitors of ATP citrate lyase cause citrate to rise and inhibit glycolysis via PFK 1 |
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What are the 4 main sites for glycogen storage disorders?
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1) Debranching enzyme
2) Branching enzyme 3) Glucose 6 phosphatase 4) Glycogen phosphorylase |
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What is the other pathway for degradation of glycogen and what enzyme is involved in that pathway?
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The lysosomal pathway and the enzyme is alpha 1,4 glucosidase
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What do you see in Von Gerke's Disease? Which organ is effected most?
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Increased amount of glycogen, can't get free glucose because defect in glucose 6 phosphatase or transport system
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What do you see in Pompe's Disease? Which organ is effected most?
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This is lysosomal. See meassive amounts of normal glycogen. Alpha 1,4 glucosidase is messed up. Die before age 2. All organs effected.
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What do you see with Cori's Disease? Which enzyme is effected?
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You see an increased amount of short branched glycogen. Problem with the debranching enzyme. Not fatal.
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What do you see with Anderson's Disease? Which enzyme and organs are effected most?
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You see a normal amount of long branched glycogen. The liver and spleen are effected. Problem with the branching enzyme. See cirrhosis of the liver.
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What do you see with Mcarole's Disease? What enzyme and organ are effected most?
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When you want to call forth glycogen as a source of energy you exhaust the capacity. The muscle is effected. Problem with the phosphorylase enzyme.
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What is the lipid carrier in n-linked glycoprotein synthesis?
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Dolichol
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What are the two types of oligosaccaride chains that determine where the glycoprotein ends up?
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High mannose and complex
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What will enzymes that are destine for the lysosome have?
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High mannose chains
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What is the key that takes glycoprotiens from the golgi to the lysosome?
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Mannose 6 phosphate receptor
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What does a patient with inclusion disease lack?
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The mannose 6 phosphate residues on the glycoprotein to guide to the lysosome
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What is the enzyme that is missing in inclusion disease?
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A phosphotransferase to get the phosphate on mannose 6 phosphate
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What gives a glycoprotein its negative charge?
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Sialic acid
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