How can glycolysis proceed under anaerobic conditions when a key step in the process involves the oxidation of phosphoglyceraldehyde PGAL?
Glycolysis is a metabolic pathway that converts glucose into two molecules of pyruvate. It occurs in the cytoplasm of cells and does not require oxygen. One of the key steps in glycolysis is the oxidation of phosphoglyceraldehyde (PGAL) to 1,3-bisphosphoglycerate (BPG). This reaction is catalyzed by the enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH).
Under anaerobic conditions, GAPDH is unable to transfer electrons to NAD+ because NAD+ is already reduced. Instead, GAPDH uses an inorganic phosphate (Pi) as the electron acceptor. This reaction produces BPG and NADH. The NADH can then be used to reduce other molecules, such as pyruvate.
The overall reaction of glycolysis under anaerobic conditions is:
$$\text{Glucose} + 2 \text{NAD}^+ + 2 \text{ADP} + 2 \text{Pi} \longrightarrow 2 \text{Pyruvate} + 2 \text{NADH} + 2 \text{ATP} + 2 \text{H}_2\text{O}$$
This reaction is less efficient than glycolysis under aerobic conditions, but it allows the cell to continue to generate ATP in the absence of oxygen.
Related Questions:
- What is glycolysis?
- Glycolysis is a metabolic pathway that converts glucose into two molecules of pyruvate.
- What is the key step in glycolysis?
- The key step in glycolysis is the oxidation of phosphoglyceraldehyde (PGAL) to 1,3-bisphosphoglycerate (BPG).
- What enzyme catalyzes the oxidation of PGAL?
- The enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH) catalyzes the oxidation of PGAL.
- What happens to NADH under anaerobic conditions?
- NADH is used to reduce other molecules, such as pyruvate.
- Is glycolysis less efficient under anaerobic conditions?
- Yes, glycolysis is less efficient under anaerobic conditions.
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