24 Questions
What is the primary function of glyceraldehyde-3-phosphate dehydrogenase in the ED pathway?
To catalyze the oxidation of glyceraldehyde-3-phosphate by NAD+
What is the net yield of ATP molecules per glucose molecule in the ED pathway?
1 ATP, 1 NADH, and 1 NADPH
What is the enzyme responsible for converting 2-phosphoglycerate to phosphoenolpyruvate (PEP)?
Enolase
What is the product of the substrate-level phosphorylation reaction catalyzed by phosphoglycerate kinase?
ATP
What is the primary function of NAD+ in the ED pathway?
To oxidize glyceraldehyde-3-phosphate, generating NADH
What is the final product of the ED pathway?
Pyruvate
What is the reactant that donates a phosphate group to ADP in the final step of the ED pathway?
Phosphoenolpyruvate (PEP)
In which step of the ED pathway is the enzyme phosphoglycerate mutase involved?
Step 8: Isomerization
Which enzyme is absent in some microorganisms that use the Entner-Doudoroff pathway instead of glycolysis?
Phosphofructokinase
What is the primary reason why the Entner-Doudoroff pathway is used by some bacteria instead of glycolysis?
Due to the lack of essential enzymes for glycolysis
Which of the following microorganisms is a rare exception among Gram-positive bacteria that use the Entner-Doudoroff pathway?
Enterococcus faecalis
What is the primary role of KDPG Aldolase in the Entner-Doudoroff pathway?
To catalyze the cleavage of 2-keto-3-deoxy-6-phosphogluconate
Which of the following organisms has been found to use the Entner-Doudoroff pathway as its main pathway for providing energy?
Xanthomonas campestris
What is the end product of glucose phosphorylation in the Entner-Doudoroff pathway?
2-keto-3-deoxy-6-phosphogluconate
Which of the following compounds is a byproduct of the Entner-Doudoroff pathway?
NADPH
What is the net ATP yield per glucose molecule in the Entner-Doudoroff pathway?
Less than 1 ATP
What is the net ATP yield per glucose molecule in the Entner-Doudoroff pathway?
1 ATP
What is the byproduct of the oxidation of glucose-6-phosphate in the Entner-Doudoroff pathway?
NADPH
What enzyme is involved in the dehydration of 6-phosphogluconate to form 2 keto 3-deoxy-6-phosphogluconate?
6-phosphogluconate dehydratase
What is the end product of the Entner-Doudoroff pathway that enters the TCA cycle?
Pyruvate
What enzyme is involved in the cleavage of KDPG to form pyruvate and glyceraldehyde-3-phosphate?
KDPG aldolase
What is the fate of glyceraldehyde-3-phosphate formed in the Entner-Doudoroff pathway?
It enters the glycolysis pathway
What is the enzyme responsible for the phosphorylation of glucose in the Entner-Doudoroff pathway?
Hexokinase
What is the ATP requirement for the phosphorylation of glucose in the Entner-Doudoroff pathway?
1 ATP and 1 Mg2+
Study Notes
Entner-Doudoroff Pathway
- A metabolic pathway that catabolizes glucose to pyruvate, with a net yield of 1 ATP, 1 NADH, and 1 NADPH per glucose molecule.
- Uses unique enzymes, including 6-phosphogluconate dehydratase aldolase and 2-keto-deoxy-6-phosphogluconate (KDPG) aldolase, in addition to common metabolic enzymes.
Steps in the Entner-Doudoroff Pathway
- Step 1: Phosphorylation - Glucose is converted to glucose-6-phosphate by hexokinase enzyme, requiring ATP and Mg2+.
- Step 2: Oxidation - Glucose-6-phosphate is oxidized to 6-phosphogluconolactone by glucose-6-phosphate dehydrogenase, a NADP-dependent enzyme, yielding NADPH + H+.
- Step 3: Hydration - 6-Phosphogluconolactone is converted to 6-phosphogluconic acid by hydrolase.
- Step 4: Dehydration - 6-Phosphogluconate is dehydrated to form 2-keto-3-deoxy-6-phosphogluconate (KDPG) by 6-phosphogluconate dehydratase.
- Step 5: Cleavage of KDPG - KDPG is converted to pyruvate and glyceraldehyde-3-phosphate by KDPG aldolase.
- Step 6: Oxidation and Phosphorylation - Glyceraldehyde-3-phosphate is oxidized by NAD+ and phosphorylated by adding a free phosphate group, forming 1,3-bisphosphoglycerate.
- Step 7: Substrate-level phosphorylation - 1,3-Bisphosphoglycerate is converted to 3-phosphoglycerate by phosphoglycerate kinase (PGK), yielding ATP.
- Step 8: Isomerization - 3-Phosphoglyceric acid is converted to 2-phosphoglyceric acid by phosphoglyceromutase.
- Step 9: Dehydration - 2-Phosphoglycerate is converted to phosphoenolpyruvate (PEP) by enolase.
- Step 10: Substrate-level phosphorylation - PEP is converted to pyruvate by pyruvate kinase, yielding ATP.
Organisms that Use the Entner-Doudoroff Pathway
- Found in certain Gram-negative bacteria, such as Pseudomonas, Rhizobium, Azotobacter, and Agrobacterium.
- Rarely found in Gram-positive bacteria, with Enterococcus faecalis being an exception.
- Examples of bacteria that use the ED pathway include Pseudomonas, Azotobacter, Rhizobium, Agrobacterium, Escherichia coli, Enterococcus faecalis, Zymomonas mobilis, and Xanthomonas campestris.
- Also found in some cyanobacteria, ferns, algae, mosses, and plants, including Hordeum vulgare.
This quiz assesses your understanding of the Entner-Doudoroff pathway, a metabolic pathway that breaks down glucose to pyruvate, producing ATP, NADH, and NADPH. Learn about the distinct features and enzymes involved in this process.
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