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.Which fate of pyruvate is an anaerobic process? A)Formation of alanine B)Formation of oxaloacetate C)Formation of acetyl CoA D)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 Gluconeogenesis Amino acid and nitrogen metabolism Aerobic Energy Anaerobic in microorganisms Anaerobic in higher organisms

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 37 o with ions Problem?

Actual Free energy Irreversible reactions: Which type of enzymes? Near-equilibrium reactions Notice: reactions 5 and 6 together

Answers 1.A 2.D 3.D 4.D 5.B