Entner-Doudoroff Pathway: Videos & Practice Problems

The Entner-Doudoroff pathway (EDP) is an alternative glycolytic pathway utilized by some bacteria, distinct from eukaryotic glycolysis. It features a single ATP investment, yielding one G3P molecule, which leads to the production of one NADH and one net ATP during the energy harvest phase. A key product of the EDP is NADPH, crucial for biosynthetic reactions, unlike the traditional glycolysis that produces no NADPH. Ultimately, both pathways generate two pyruvate molecules, but the EDP's efficiency is halved in terms of NADH and ATP production.

Entner-Doudoroff Pathway

The Entner-Doudoroff pathway (EDP) is an alternative glycolytic pathway utilized by certain bacteria, distinct from the glycolysis pathway found in eukaryotes. This pathway serves as a substitute for the energy investment phase of glycolysis, allowing bacteria to convert glucose into pyruvate while producing essential molecules, including NADPH, which is crucial for biosynthetic reactions within the cell.

In contrast to the traditional glycolysis pathway, which requires the investment of two ATP molecules during its energy investment phase, the EDP only requires one ATP molecule. This results in the production of a single glyceraldehyde-3-phosphate (G3P) molecule, rather than the two G3P molecules generated in standard glycolysis. The G3P produced in the EDP can then proceed to the energy harvest phase, albeit yielding only half the amount of NADH and ATP compared to the conventional pathway. Specifically, the EDP produces one NADH and one net ATP, as opposed to the two NADH and two net ATP produced in normal glycolysis.

Another key distinction is the production of NADPH, which is exclusively generated through the Entner-Doudoroff pathway. This differentiates it from the standard glycolysis pathway, which does not produce NADPH. The overall products of the EDP include one NADPH, one G3P, one NADH, one net ATP, and ultimately two pyruvate molecules. The second pyruvate is formed through an alternative mechanism within the EDP, ensuring that the total number of pyruvates remains consistent with that of traditional glycolysis.

In summary, the Entner-Doudoroff pathway is a unique metabolic route for certain bacteria, allowing them to efficiently convert glucose into pyruvate while generating NADPH for vital cellular processes. Understanding this pathway enhances our comprehension of bacterial metabolism and its differences from eukaryotic glycolysis.

The Entner-Doudoroff Pathway:

• A. Converts glucose to pyruvate.
• B. Can operate aerobically or anaerobically.
• C. Is an alternative process to the glycolytic pathway.
• D. All the above are correct.

Answer: (D)

The Entner-Doudoroff pathway leads to the formation of:

• A. ATP.
• B. Pyruvate.
• C. NADH.
• D. NADPH.
• E. All of the above.

Answer: (E)

Here’s what students ask on this topic:

What is the Entner-Doudoroff pathway and how does it differ from glycolysis?

The Entner-Doudoroff pathway (EDP) is an alternative glycolytic pathway used by some bacteria, but not by eukaryotes. Unlike the traditional glycolysis pathway, which has an energy investment phase requiring 2 ATP molecules, the EDP only invests 1 ATP molecule. This results in the production of one glyceraldehyde-3-phosphate (G3P) molecule, leading to the generation of one NADH and one net ATP during the energy harvest phase. A key distinguishing feature of the EDP is the production of NADPH, an important electron carrier for biosynthetic reactions, which is not produced in traditional glycolysis. Both pathways ultimately generate two pyruvate molecules, but the EDP is less efficient in terms of NADH and ATP production.

Why is NADPH important in the Entner-Doudoroff pathway?

NADPH is a crucial product of the Entner-Doudoroff pathway because it serves as an important electron carrier involved in biosynthetic reactions. These reactions are essential for building molecules and structures within the cell. Unlike NADH, which is primarily used in energy production, NADPH provides the reducing power needed for anabolic processes, such as fatty acid synthesis and nucleotide synthesis. The production of NADPH in the EDP distinguishes it from the traditional glycolysis pathway, which does not produce NADPH.

Which organisms utilize the Entner-Doudoroff pathway?

The Entner-Doudoroff pathway is utilized by some bacteria, including both Gram-negative and Gram-positive species. Examples of bacteria that use this pathway include Pseudomonas, Azotobacter, and Zymomonas. This pathway is not found in eukaryotes. The EDP allows these bacteria to metabolize glucose and other carbohydrates efficiently, especially in environments where the traditional glycolysis pathway may not be as advantageous.

How does the ATP yield of the Entner-Doudoroff pathway compare to glycolysis?

The ATP yield of the Entner-Doudoroff pathway is lower compared to traditional glycolysis. In the EDP, only one ATP molecule is invested, resulting in the production of one glyceraldehyde-3-phosphate (G3P) molecule. This leads to the generation of one NADH and one net ATP during the energy harvest phase. In contrast, traditional glycolysis invests two ATP molecules and produces two G3P molecules, leading to the generation of two NADH and a net gain of two ATP molecules. Therefore, the EDP produces half the amount of NADH and ATP compared to glycolysis.

What are the main products of the Entner-Doudoroff pathway?

The main products of the Entner-Doudoroff pathway include one NADPH, one NADH, one net ATP, and two pyruvate molecules. The production of NADPH is a key distinguishing feature of the EDP, as it is not produced in traditional glycolysis. NADPH is essential for biosynthetic reactions, providing the reducing power needed for anabolic processes. The pathway also produces one NADH and one net ATP, which are used in cellular energy production. Despite the lower efficiency in terms of NADH and ATP production, the EDP still generates two pyruvate molecules, similar to glycolysis.