The oxidation of glyceraldehyde- 3 -phosphate to 1,3...

Name: Problem 9, Chapter 24: Organic Chemistry
Uploaded: 2020-08-19T18:01:49-08:00
Duration: 47 s
Channel: Yokshitha Reddy Bathula
Description: The oxidation of glyceraldehyde- 3 -phosphate to 1,3 -bisphosphoglycerate is an endergonic reaction, but the flow through this point in glycolysis proceeds smoothly. How is the unfavorable equilibrium constant overcome?

The oxidation of glyceraldehyde- 3 -phosphate to 1,3 -bisphosphoglycerate is an endergonic reaction, but the flow through this point in glycolysis proceeds smoothly. How is the unfavorable equilibrium constant overcome?

Key Concepts

Reaction Coupling

This concept involves pairing an energetically unfavorable reaction with one that is energetically favorable so that the overall process becomes thermodynamically feasible. In biochemical pathways, the unfavorable step is essentially 'pulled' forward by the simultaneous occurrence of a reaction that has a large negative free energy change, allowing the cell to drive processes that would otherwise not proceed.

Energy Coupling in Metabolism

In metabolic pathways, reactions that require an input of energy (endergonic reactions) are often coupled to reactions that release energy (exergonic reactions). This coupling ensures that the overall change in free energy is negative, meaning the process can occur spontaneously. In glycolysis, for example, the high-energy phosphate bond formed in one reaction is later utilized to produce ATP, which helps to drive the preceding endergonic step forward.

Substrate-Level Phosphorylation

This process is a specific form of energy coupling in which a phosphate group is directly transferred from a high-energy substrate to ADP to form ATP. The formation of a high-energy intermediate, despite occurring via an endergonic reaction, is swiftly followed by the production of ATP, which provides the thermodynamic pull needed to overcome the unfavorable equilibrium.

Le Chatelier’s Principle in Biochemical Pathways

Le Chatelier’s Principle states that a system at equilibrium will shift in a direction that tends to reduce any perturbation. In metabolism, if a product of a reaction is rapidly consumed in a subsequent step, the equilibrium of the initial reaction is shifted towards product formation. This consumption of the intermediate drives the entire pathway forward, effectively overcoming a poor equilibrium constant in any single step.

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