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31 Cards in this Set
- Front
- Back
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overview of glycolysis
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degrade glu and simple sugars
carried out by all living cells anaerobic cytosolic process short term E source, limited O2 provide precursors for aerobic cata |
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more glycolysis facts
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10 rxns all different rates
two phases: 1.converts glu(6C) to two glyceraldegyde-3-P (3C) 2.pduces 2 pyruvate (3C) pdts:pyruvate,ATP,NADH |
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first phase of glycolysis
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1st rxn:P-ylation of glu
hexokinase or glucokinase a priming rxn:ATP is consumed ATP makes P-lyation spontaneous (5 rxns,need 2ATP,get G-3-P) |
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hexokinase (normally active)
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1st step, large delta G (neg)
act to p-ylate glu & keep in the cell glu Km=.1mM,cell has 4mM glu allosterically inhibited by pdt glu-6-P |
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glucokinase
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another enzyme
Km=10mM, only turns on when cell is rich in glu |
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advantages of phosphorylating glucose
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keeps it in cell
keeps [glu] low favors diffusion of glu into cell |
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glucokinase
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Km=10mM
only in liver p-ylates glu to G-6-P but only when liver glu is high G-6-P in liver as glycogen inducible by insulin |
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diabetes mellitus
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(insufficient insulin)
low glucokinase cant tolerate high levels of glu pduce little glycogen |
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reaction 2:phosphoglucoisomerase
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glu-6-P to fru-6-P
isomerization rxn to: eases next p-ylation at C-1 set up aldol cleavage at C-3 |
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reaction 3:phosphofructokinase
(PFK) |
commited step in glycolysis
high -deltaG,and regulated ATP inhibits,AMP reverses citrate=allosteric inhibitor fru-2,6-bisP=allosteric activator PFK incr activity when E is low |
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PFK's actual rxn
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commits to metabolising glu as opposed to conversion to another sugar or storage
is the most important regulation site regulation couples glycolysis to citric acid cycle |
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fructose-2,6-bisphosphate
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increases phosphofructokinase activity
its the potent allosteric activator of PFK increases affinity of PFK for F-6-P also reverse PFK inhibition by ATP |
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reaction 4:aldolase
+ delta G |
cleaves to fru-1,6-bisP (FBP)
yields:DHAP and gly-3-P animal aldolases:classI class I:form covalent schiff base intermediate bw S and active site lysine |
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reaction 5:triose phosphate isomerase
+ delta G (tho less than rxn 4) |
DHAP to gly-3-P
a near-perfect enzyme catalytic rate is limited by substrate interaction completes 1st phase of glycolysis |
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glycolysis 2nd phase
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metabolic E pduces 4ATP
net ATP yield is 2 involves 2 very high energy P intermediates: 1,3-bisphophoglycerate(1,3-BPG) phophoenolpyruvate |
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phase 2 of glycolysis
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two glyceraldehyde-3-P converted to 2 pyruvates
rxns yield 4ATP |
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reaction 6:glyceraldegyde-3-dehydrogenase
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G-3-P is oxidized to 1,3-BPG
E yield from an aldehyde to carboxylic acid is used to make 1,3-BPG and NADH mechanism involves covalent catalysis and nicotinamide coenzyme |
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NAD+ and NADP+ two-electron transfer rxns
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the dependent dehydrogenases catalyze 6 diff rxns
oxidized:NAD+,NADP+ reduced:NADH,NADPH |
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reaction 7:phophoglycerate kinase (PGK)
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ATP synthesis from a high-E P
substrate level phosphorylation break even rxn for ATP |
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PGK rxn results
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transfer of phosphoryl group from 1,3-BPG to ADP to form ATP which pays off ATP debt
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reaction 8:phosphoglycerate mutase
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phosphoryl group from C-3 to C-2
enzyme repositions the P to make phosphoenolpyruvate (PEP) mutase:catalyze migration of functional group w/i substrate |
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reaction 8 rxn
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3-phosphoglycerate to 2-phosphoglycerate
low + delta G |
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reaction 9:enolase
low + delta G (lower than 8's) |
2-phosphoglycerate(2-P-gly) to phosphoenolpyruvate(PEP)
makes a high-E P in prep for ATP synthesis enolase rearranges so more E can be released in hydrolysis |
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reaction 10:pyruvate kinase
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PEP to pyruvate makes ATP
transfer phosphoryle from PEP to ADP substrate level p-ylation the 2ATP are payoff of glycolysis high - delta G, regulated activated by AMP and fru-1,6-bisP inhibited by ATP and acetyl-CoA |
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fate of NADH(aer or ana)
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[is energy]
1.w/ O2, re-oxidized in e- transport, making ATP in oxidative p-ylation 2.no O2, re-oxidized by lactate dehydrogenase (LDH) giving more NAD+ for glycolysis |
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fate of pyruvate (ana or aer)
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aerobic:citric acid cycle
anaerobic:lactose dehydrogenase makes lactate |
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anaerobic fate of pyruvate
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fermentation:
yeast=alchol mammals=lactic acid |
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lactate accumulation in exercising tissues
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strenous=anaerobic
represents end of glycolysis in anaerobic muscle tissue cramps,fatigue lactate resynthesized to glu breakdown of pyruvate |
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energetics of glycolysis
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both + and - delta G
delta G in cells: most values near zero 3/10 rxns=high - delta G's which are sites of regulation |
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comparison of free energy changes in glycolysis
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rxns 2,4-9 delta G close to 0
rxns depend on [substrate] hexokinase,PFK,pyruvate kinase (1,3,10) have high - delta G's (inhibition of any one brings glycolysis to a halt) |
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other substrates for glycolysis
(fructose,mannose,galactose) |
fru and mann:routed into glycolysis by conventional means
gal:uses leloir pathway that converts gal to glu |
