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31 Cards in this Set

  • Front
  • Back
overview of glycolysis
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
more glycolysis facts
10 rxns all different rates
two phases:
1.converts glu(6C) to two glyceraldegyde-3-P (3C)
2.pduces 2 pyruvate (3C)
first phase of glycolysis
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)
hexokinase (normally active)
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
another enzyme
Km=10mM, only turns on when cell is rich in glu
advantages of phosphorylating glucose
keeps it in cell
keeps [glu] low
favors diffusion of glu into cell
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
diabetes mellitus
(insufficient insulin)
low glucokinase
cant tolerate high levels of glu
pduce little glycogen
reaction 2:phosphoglucoisomerase
glu-6-P to fru-6-P
isomerization rxn to:
eases next p-ylation at C-1
set up aldol cleavage at C-3
reaction 3:phosphofructokinase
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
PFK's actual rxn
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
increases phosphofructokinase activity
its the potent allosteric activator of PFK
increases affinity of PFK for F-6-P
also reverse PFK inhibition by ATP
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
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
glycolysis 2nd phase
metabolic E pduces 4ATP
net ATP yield is 2
involves 2 very high energy P intermediates:
phase 2 of glycolysis
two glyceraldehyde-3-P converted to 2 pyruvates
rxns yield 4ATP
reaction 6:glyceraldegyde-3-dehydrogenase
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
NAD+ and NADP+ two-electron transfer rxns
the dependent dehydrogenases catalyze 6 diff rxns
reaction 7:phophoglycerate kinase (PGK)
ATP synthesis from a high-E P
substrate level phosphorylation
break even rxn for ATP
PGK rxn results
transfer of phosphoryl group from 1,3-BPG to ADP to form ATP which pays off ATP debt
reaction 8:phosphoglycerate mutase
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
reaction 8 rxn
3-phosphoglycerate to 2-phosphoglycerate
low + delta G
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
reaction 10:pyruvate kinase
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
fate of NADH(aer or ana)
[is energy]
1.w/ O2, re-oxidized in e- transport, making ATP in oxidative p-ylation O2, re-oxidized by lactate dehydrogenase (LDH) giving more NAD+ for glycolysis
fate of pyruvate (ana or aer)
aerobic:citric acid cycle
anaerobic:lactose dehydrogenase makes lactate
anaerobic fate of pyruvate
mammals=lactic acid
lactate accumulation in exercising tissues
represents end of glycolysis in anaerobic muscle tissue
lactate resynthesized to glu
breakdown of pyruvate
energetics of glycolysis
both + and - delta G
delta G in cells:
most values near zero
3/10 rxns=high - delta G's which are sites of regulation
comparison of free energy changes in glycolysis
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)
other substrates for glycolysis
fru and mann:routed into glycolysis by conventional means
gal:uses leloir pathway that converts gal to glu