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23 Cards in this Set
- Front
- Back
3 Fates of glucose
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1.) storage to glycogen, starch, and sucrose
2.) oxidation via glycolysis to make pyruvate 3.) oxidation by pentose phosphate pathway to make ribose 5-phosphate |
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Preparatory phase
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phosphorylation of glucose and its conversion to glyceraldehyde 3-phosphate
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Payoff phase
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oxidative conversion of glyceraldehyde 3-phosphate to pyruvate and the coupled formatin of ATP and NADH
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Step 1: Phosphorylation of Glucose
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- Glucose phosphorylation at C-6 making Glucose 6-phosphate
- use 1 ATP - catalyzed by hexokinase - 1st irreversible and regulated step |
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Step 2: Conversion of G6P to what?
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- G6P to Fructose 6-phosphate
- catalyzed by Phophohexose Isomerase - reversible |
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Step 3: Phosphorylation of F6P to what?
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- phosphorylation of F6P to Fructose 1,6-bisphosphate
- use 1 ATP - catalyzed by Phosphofructokinase-1 - 2nd irreversible - major point of regulation |
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Step 4: Cleavage of F16BP to what?
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- cleavage of F16BP to Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
- catalyzed by Aldolase - reversible |
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Step 5: Interconversion of the triose phosphates
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- Dihydroxyacetone phosphate is converted to Glyceraldehyde 3-phosphate by Triose phosphate isomerase
- reversible |
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Step 6: Oxidation of Glyceraldehyde 3-phosphate to what?
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- oxidation of glyc3P to 1,3-bisphosphoglycerate
- glyc3P is phosphorylated with inorganic phophate - catalyzed by Glyceraldehyde 3-phosphate dehydrogenase - reduction of NAD+ (electron acceptor) to NADH and H+ - free energy conserved in phosphate group formation - reversible - everything x2 |
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Step 7: Phophoryl transfer from 13BPG to ADP
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- generate 2 ATP
- phosphoryl grp from 13BPG donated to ADP to make ATP - forms 3-Phospoglycerate - catalyzed by phophoglycerate kinase (named for the reversible rxn) |
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Step 8: 3-Phosphoglycerate what?
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- 3-Phosphoglycerate to 2-Phosphoglycerate
- catalyzed by phophoglycerate mutase - reversible |
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Step 9: Dehydration of 2-Phosphoglycerate to what?
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- 2-Phosphoglycerate to Phosphoenolpyruvate
- removes H2O causes redistribution of energy - has high phosphoryl grp transfer potential - reversible |
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Step 10: Transfer of phosphoryl group from Phosphoenolpyruvate to ADP
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- PEP donates its Pi group to ADP making ATP and pyruvate
- catalyzed by pyruvate kinase - makes 2 more ATPs - 3rd irreversible step and regulated |
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3 enzymes that are regulated
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1.) hexokinase
2.) phosphofructokinase-1 3.) pyruvate kinase |
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How is energy conserved in glycolysis?
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- by the couple phosphorylation of 4 ADP to ATP by high energy cps
- in formation of 2 NADH per 1 glucose |
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What are the products of glycolysis?
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- 2 pyruvates
- 2 ATP - 2 NADH |
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3 Fates of pyruvate
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1.) in anaerobic conditions, fermentation to alcohol and yeast
2.) in aeobic, oxidized to Acetyl-CoA to be put in TCA 3.) in anaerobic, fermentation to lactate in vigorously contracting muscles * lactate can be used to reoxidize NADH |
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Importance of phosphorylated intermediates
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- are charged at pH 7, therefore can't leave the cell
- phosphorylation is a form of conservation of energy through the phosphate bond - energy derived from binding the phosphate grp to the active site helps lower the activation energy for the rxn |
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How does lactose entery glycolysis?
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- lactose turn into glucose and galactose (which can be turned in to glucose)
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Conversion of galactose to glucose
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- galactose phosphorylated at C-1 using 1 ATP
- add urindine diphosphate nucleotide - UPD-galactose converted to UPD-glucose by oxidation of C-4 by NAD+, then reduction of C-4 by NADH - UPD-glucose recycled to get Glucose 1-Phosphate - G1P converted to G6P by phophoglucomutase, which can then enter glycolysis |
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How does glycogen enter glycolysis?
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- breakdown of glycogen to G1P
- glycogen phosphorylase attacks nonreducing glycosidic link end - G1P turn to G6P to enter glycolysis |
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How does sucrose enter glycolysis?
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- sucrose can be broken down to glucose and fructose
- fructose can bypass and enter at F6P in glycolysis when catalyzed by hexokinase - fructose can turn into F1P then glyceraldehyde and dihydroxyacetone phosphate then to Glyceraldehyde 3-phosphate where it enters in glycolysis |
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How does trehalose enter glycolysis?
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- trehalose breaks down to glucose which can enter glycolysis
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