Transcript Pyruvate and Energetics of Glycolysis

Pyruvate and Energetics of
Glycolysis
C483 Spring 2013
1. The conversion of pyruvate to ethanol also causes the ________.
A) oxidation of NADH
B) production of ADP
C) consumption of O2
D) generation of an ion gradient across mitochondrial membranes
2. The enzyme that catalyzes the conversion of pyruvate to lactate is ________.
A) lactate reductase
B) pyruvate kinase
C) lactoenolpyruvate
D) lactate dehydrogenase
3.
A)
B)
C)
D)
Which fate of pyruvate is an anaerobic process?
Formation of alanine
Formation of oxaloacetate
Formation of acetyl CoA
Formation of lactate
Seven of the ten reactions in the glycolytic pathway have free energy values
close to zero. What does this tell us about those reactions?
A) They are near equilibrium reactions.
B) They are not control points for pathway regulation.
C) They are reversible reactions.
D) All of the above.
E) None of the above.
Which of the following is false concerning steps 1, 3, and 10 of glycolysis?
A) All are catalyzed by a kinase.
B) All involve ATP hydrolysis
C) All have a negative standard free energy
D) All have a negative free energy under cellular conditions
E) All are irreversible steps.
Fate of Pyruvate
Anaerobic in
microorganisms
Gluconeogenesis
Anaerobic in
higher organisms
Amino acid
and nitrogen
metabolism
Aerobic Energy
The Problem of Anaerobic Metabolism
• With oxygen, the NADH produced in glycolysis
is re-oxidized back to NAD+
• NAD+/NADH is a co-substrate which means…
• If there is no oxygen, glycolysis will stop
because…
• The solution to the problem is to…
The solution in Yeast
• Pyruvate is decarboxylated
(cofactor?) to acetaldehyde
• Acetaldehyde transformed to
ethanol
– What type of reaction?
– What cofactor?
• NAD+ is regenerated to be
reused in GAPDH
Balanced Anaerobic Equation
Glycolysis:
+
Ethanol:______________________________
The Solution in Us
• Lactate formation
• Balanced equation
• Do the same exercise as yeast
Overall Energetics of Glycolysis
• Standard Free energy change, and standard
free energy change at 37o with ions
• Problem?
Actual Free energy
• Irreversible
reactions: Which
type of enzymes?
• Near-equilibrium
reactions
• Notice: reactions 5
and 6 together
Answers
1.
2.
3.
4.
5.
A
D
D
D
B