During the second half of glycolysis, what occurs?

General
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during the second half of glycolysis, what occurs?

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During the second half of glycolysis, what occurs?

Answer:

In the second half of glycolysis, often referred to as the energy payoff phase, several important reactions occur that lead to the production of ATP and NADH. Here’s a detailed breakdown of this phase:

Solution By Steps:

  1. Production of 1,3-Bisphosphoglycerate:

    • Glyceraldehyde 3-phosphate (G3P) is oxidized, and NAD⁺ is reduced to NADH.
    • This reaction is catalyzed by the enzyme glyceraldehyde 3-phosphate dehydrogenase.
    • An inorganic phosphate is added, forming 1,3-bisphosphoglycerate.
    \text{G3P} + \text{NAD}^+ + \text{Pi} \rightarrow \text{1,3-bisphosphoglycerate} + \text{NADH} + \text{H}^+

  2. ATP Generation from 1,3-Bisphosphoglycerate:

    • 1,3-bisphosphoglycerate donates a high-energy phosphate to ADP, producing ATP and 3-phosphoglycerate.
    • This step is catalyzed by the enzyme phosphoglycerate kinase.
    • This is one of the substrate-level phosphorylation steps where ATP is directly generated from ADP.
    \text{1,3-bisphosphoglycerate} + \text{ADP} \rightarrow \text{3-phosphoglycerate} + \text{ATP}

  3. Formation of Phosphoenolpyruvate (PEP):

    • The molecule undergoes a series of isomerization and dehydration to form phosphoenolpyruvate.
    • Enzymes involved include phosphoglycerate mutase and enolase.
    \text{3-phosphoglycerate} \rightarrow \text{2-phosphoglycerate} \rightarrow \text{phosphoenolpyruvate}

  4. Final ATP Generation and Pyruvate Formation:

    • Phosphoenolpyruvate donates a high-energy phosphate to ADP, yielding another ATP and forming pyruvate.
    • This reaction is catalyzed by the enzyme pyruvate kinase.
    \text{Phosphoenolpyruvate} + \text{ADP} \rightarrow \text{Pyruvate} + \text{ATP}

Summary:

  • Two molecules of ATP are produced per molecule of glucose in the steps involving substrate-level phosphorylation.
  • Two molecules of NADH are generated when glyceraldehyde 3-phosphate is oxidized.
  • The net gain of ATP from glycolysis is two molecules, as two ATP were consumed in the first half of glycolysis.

This phase of glycolysis is crucial because it produces ATP and NADH, which are used in cellular energy metabolism.