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First Reaction
- -start with glucose
- -phosphorylation reaction
- -C6 becomes phosphorylated
- -only occurs in forward direction
- -hexokinase 1 is enzyme(can phosphorylate and hexose sugar, is inhibited by product G6P....km of .1milimolar)
- -produces glucose-6-phosphate
- -can also be catalyzed by glucokinase (km of 5-10 milimolar) not inhibited by product this way and only occurs in liver, does not occur in diabetics
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Second Reaction
- -start with G6P
- -conversion of aldose(double bonded O on C1)-->ketose sugar(double bonded O on C2)
- -can occur in reverse direction, but specific to G6P and Fructose 6 Phosphate
- -phosphohexose isomerase enzyme
- -product is Fructose 6 Phosphate F6P
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Third Reaction
- -start with F6P
- -enzyme phosphofructokinase 1
- -energy requiring
- -simple addition of phosphate group to C1
- -only occurs in forward direction
- -only occurs when cell needs energy (gatekeeper reaction)
- -product Fructose 1,6 Bisphosphate (bis-means has two phosphates, but not connected di-means has two phosphates attached to each other)
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Reaction Four
- -start with Fructose 1,6 Bisphosphate
- -conversion of 6C sugar into two 3C sugars
- -enzyme aldolase
- -reversible reaction
- -products Glyceraldehyde 3-Phosphate (aldose sugar) and Dihydroxyacetone phosphate(ketose sugar, starting point for synthesis of glycerol backbone for lipids)
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Reaction Five
- -start Dihydroxyacetone phosphate
- -reversible reaction
- -conversion of ketose to aldose sugar
- -enzyme triose phosphate isomerase
- -product Glyceraldehyde 3-phosphate
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Reaction 6
- -start Glyceraldehyde 3-phosphate
- -oxidation and then phosphorylation with NAD+ being reduced to NADH+ and H+ using inorganic phosphate as energy (each NADH+ is worth 2.5 ATP so nets 5 ATP equivalent from reaction)
- -enzyme is glyceraldehyde 3-phosphate dehydrogenase
- -produces 1,3 bisphosphoglycerate
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Reaction Seven
- -start with 1,3 bisphosphoglycerate (high energy molecule, but very unstable)
- -transfers phosphate group to ADP, forming ATP
- -enzyme phosphoglycerate kinase
- -reversible reaction
- -substrate level phosphorylation because ATP is directly created
- -product 3-phosphoglycerate
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Reaction Eight
- -start 3-phosphoglycerate
- -transfer of phosphate from C3 to C2
- -reversible reaction
- -enzyme phosphoglycerate mutase(all enzymes that move a group to different location on same molecule are known as mutases)
- -product 2-phosphoglycerate
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Reaction Nine
- -start 2-phosphoglycerate
- -dehydration reaction
- -enzyme enolase(inhibited by floride)
- -reversible reaction
- -product phosphoenolpyruvate
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Reaction Ten
- -start phosphoenolpyruvate
- -produces 2 ATP (substrate level phosphorylation)
- -enzyme pyruvate kinase
- -only goes in forward reaction
- -product Pyruvate
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Seven Types of Reactions
- -phosphoryl transfer-->kinases (reaction 1,3,7 &10)
- -phosphoryl shift-->mutase (reaction 8)
- -isomerization-->isomerases (interconversion between aldose and ketose sugar, reactions 2 &5)
- -dehydration-->enolase (reaction 9)
- -aldol cleavage-->aldolase (reaction 4)
- -dehydrogenation-->dehydrogenase (reaction 6)
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Stage One of Glycolysis
- -5 steps
- -energy requiring (2 ATP per glucose molecule)
- -conversion of 6C glucose into two 3C glyceraldehyde
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Stage Two of Glycolysis
- -5 steps
- -energy yielding
- -4 ATP/glucose directly (substrate level phosphorylation)
- -5 ATP equivalents from reoxidation of 2 NAD+
- -net yield for stage one and stage two is 7 ATP equivalents
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- -6C glucose molecule
- -starting point for glycolytic pathway
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- -fructose 6 phosphate
- -product of reaction 2 and starting point of reaction 3
- -fructose 1,6 bisphosphate gets another phosphate group off of C1
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Hexokinase 1
- -enzyme for reaction one
- -phosphorylates hexose sugar
- -turns glucose into glucose 6 phosphate
- -only occurs in forward direction
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Phosphofructokinase 1
- -enzyme for reaction 3
- -turns fructose 6 phosphate into fructose 1,6 bisphosphate
- -only goes forward
- -gatekeeper reaction
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glyceraldehyde 3-phosphate dehydrogenase
- -enzyme for reaction 6
- -oxidates and then phosphorylates, turns glyceraldehyde 3 phosphate into 1,3 bisphosphoglycerate
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