6.7 glycolysis
DESCRIPTION
6.7 Glycolysis. Glycolysis harvests chemical energy by oxidizing glucose to pyruvate A single molecule of glucose is “cut in half” by enzymes through a series of steps to produce two molecules of pyruvate. In the process, two molecules of NAD + are reduced to two molecules of NADH - PowerPoint PPT PresentationTRANSCRIPT
6.7 Glycolysis
• Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
• A single molecule of glucose is “cut in half” by enzymes through a series of steps to produce two molecules of pyruvate.– In the process, two molecules of NAD+ are reduced to two
molecules of NADH– At the same time, two molecules of ATP are produced by substrate-
level phosphorylation
6.7 Glycolysis
• In substrate-level phosphorylation, an enzyme transfers a phosphate group from a substrate molecule to ADP… forming ATP– This ATP can be used immediately, but NADH must be
transported to the electron transport chain to generate additional ATP
6.7 Glycolysis
• MOST of the energy from Glucose is still in the pyruvate, and therefore pyruvate will move to the citric acid cycle to be further broken down.
Glucose
NAD+
+2
2 ADP
NADH2
P2
2
ATP2 +
H+
2 Pyruvate
+
ADP
ATP
Substrate
Enzyme
Product
Enzyme
P
P
P
ENERGYINVESTMENT
PHASEGlucose
Glucose-6-phosphate
Fructose-6-phosphate
Step
ADP
ATP
P
ADP
ATP
P
P
P Fructose-1,6-bisphosphate
1
2
3
Steps – A fuel molecule is energized,using ATP.
1 3
Steps – A fuel molecule is energized,using ATP.
ENERGYINVESTMENT
PHASEGlucose
Glucose-6-phosphate
Fructose-6-phosphate
Step
ADP
ATP
P
ADP
ATP
P
P
P Fructose-1,6-bisphosphate
11
2
3
3
Glyceraldehyde-3-phosphate (G3P)
Step A six-carbon intermediate splitsInto two three-carbon intermediates.
PP
44
P
P
P
P
NAD+
PP
ENERGY PAYOFF PHASE
1,3-Bisphosphoglycerate
NADH
H+
Step A redox reactiongenerates NADH.
5 55
Glyceraldehyde-3-phosphate (G3P)
PP
NAD+
NADH
H+
P
P
P
P
NAD+
PP
ENERGY PAYOFF PHASE
1,3-Bisphosphoglycerate
NADH
H+
ADP ADP
ATP ATP
3-Phosphoglycerate
2-Phosphoglycerate
P P
P P
P P
H2O H2O
ADP ADP
ATP ATP
Phosphoenolpyruvate(PEP)
Pyruvate
Step A redox reactiongenerates NADH.
Steps – ATP and pyruvateare produced.
5 55
Glyceraldehyde-3-phosphate (G3P)
PP
NAD+
NADH
H+
6
6 6
7
8
9
8
9
7
9
6.8 Pyruvate is chemically groomed for the citric acid cycle
• The pyruvate formed in glycolysis is transported to the mitochondria, where it is prepared for entry into the citric acid cycle– The first step is removal of a carboxyl group that
forms CO2
– The second is oxidization of the two-carbon compound remaining
– Finally, coenzyme A binds to the two-carbon fragment forming acetyl coenzyme A
Coenzyme A
Pyruvate Acetyl coenzyme A
CoA
NAD+ NADH H+
CO2
13
2