CHE 350 Lecture Notes - Lecture 8: Aldose, Citric Acid Cycle, Glycogen

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GLYCOLYSIS
Glycolysis converts glucose to two C3 units (pyruvate).
The free energy released in the process is harvested to synthesize ATP from ADP
+ Pi
oGlycolysis = pathway of chemically coupled phosphorylation reactions
Two Stages of Glycolysis
oStage I ) Energy Investment (Reactions 1-5)
In this prep stage, hexose glucose is phosphorylated and cleaved to
yield 2 molecules of the triose glyderaldehyde-3-phosphate (G3P) =
2 ATP CONSUMED
oStage II) Energy Recovery (Reactions 6-10)
The two molecules of G3P are converted to pyruvate, with
concomitant generation of 4 ATP. Glycolysis therefore has a net
“profit” of 2 ATP per glucose
Stage I consumes 2 ATP, Stage II produced 4 ATP  Net ATP = 2
oGlucose + 2 NAD+ + 2 ADP + 2 Pi  2 pyruvate + 2 NADH + 2 ATP +
2H2O + 4H+
STAGE I OF GLYCOLYSIS
1) Glucose  Glucose-6-phosphate (G6P)
a. Reaction catalyzed by hexokinase
b. Transfer of phosphoryl group from ATP to glucose
c. Kinase = enzyme that transfers phosphoryl groups between ATP and a
metabolite. The metabolite that serves as the phosphoryl group acceptor is
indicated in the prefix of the kinase name
d. Glucose + ATP (hexokinase with Mg2+) G6P + ADP + H+
d.i. Arrows indicate higher probability of forward reaction occurring, not
the reverse
2) G6P  Fructose-6-phosphate (F6P)
a. Reaction catalyze by phosphoglucose isomerase
b. Isomerization of an aldose to a ketose
c. Since G6P and F6P both exit predominantly in their cyclic forms, the
reaction requires ring opening, isomerization, then ring closing.
3) F6P  Fructose-1,6-bisphosphate (FBP)
a. Catalyzed by phosphofructokinase (PFK)
b. Just like step 1, just adding another phosphate
c. Bis instead of di because its two phosphate groups are not directly attached
to each other
d. F6P + ATP (PFK + Mg2+) FBP + ADP + H+
d.i. Equilibrium shifted all the way to the right, no possible reversal, will
go to completion
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Document Summary

Glycolysis converts glucose to two c3 units (pyruvate). The free energy released in the process is harvested to synthesize atp from adp. + pi: glycolysis = pathway of chemically coupled phosphorylation reactions. Two stages of glycolysis: stage i ) energy investment (reactions 1-5) In this prep stage, hexose glucose is phosphorylated and cleaved to yield 2 molecules of the triose glyderaldehyde-3-phosphate (g3p) = 2 atp consumed: stage ii) energy recovery (reactions 6-10) The two molecules of g3p are converted to pyruvate, with concomitant generation of 4 atp. Stage i consumes 2 atp, stage ii produced 4 atp net atp = 2: glucose + 2 nad+ + 2 adp + 2 pi 2 pyruvate + 2 nadh + 2 atp + Stage i of glycolysis: glucose glucose-6-phosphate (g6p, reaction catalyzed by hexokinase, transfer of phosphoryl group from atp to glucose, kinase = enzyme that transfers phosphoryl groups between atp and a metabolite.

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