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Example Question #28 : Electron Transport And Oxidative Phosphorylation
Below are standard reduction potentials of components in carbohydrate metabolism
What is the free energy change for this reaction?
First, let's consider the half reactions involved to determine .
This overall reaction involves the donation of 2 electrons, so
is defined as
. The reaction we drew earlier is shown below:
We can see that was oxidized and
was reduced. Find
.
is Faraday's constant, and is defined as:
Solve for
Example Question #1 : Oxidative Phosphorylation Energetics
Which of the following processes involved in cellular respiration has a positive Gibbs Free energy?
The final step in glycolysis
The movement of the electrons through the electron transport chain
The combination of oxaloacetate and acetyl-CoA to form citrate in the Kreb's cycle
The movement of hydrogens through ATP synthase
The pumping of hydrogens from the mitochondrial matrix to the intermembrane space
The pumping of hydrogens from the mitochondrial matrix to the intermembrane space
A positive Gibbs free energy implies that the process in question should be unfavorable under normal conditions. The only process listed that is unfavorable and requires an input of energy is the pumping of hydrogen ions into the intermembrane space. This occurs during the electron transport chain.
Example Question #2 : Oxidative Phosphorylation Energetics
In what phase of cellular respiration is not ATP produced?
Pyruvate dehydrogenase complex
Krebs cycle
Every phase of cellular respiration produces some ATP
Glycolysis
Electron transport chain
Pyruvate dehydrogenase complex
The phases of cellular respiration are glycolysis, pyruvate dehydrogenase complex, Krebs cycle, electron transport chain. Glycolysis produces a net total of 2 ATP, the Krebs cycle produces 1 GTP that is converted to ATP in another process, and the electron transport chain is where almost all of the ATP made in cellular respiration is formed. However, during the pyruvate dehydrogenase complex phase of cellular respiration, pyruvate is converted to acetyl-CoA as a preparation for the Krebs cycle, but no ATP is created.
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