Anaerobic glycolysis

Anaerobic Glycolysis

Anaerobic glycolysis is a metabolic pathway that allows cells to convert glucose into energy in the absence of oxygen. This process is crucial for cells that operate in low-oxygen environments or during intense physical activity when oxygen supply is limited. Anaerobic glycolysis results in the production of lactate and a small amount of ATP (adenosine triphosphate), which is used as an energy source by the cell.

Overview

Anaerobic glycolysis occurs in the cytoplasm of the cell and involves a series of enzymatic reactions that break down glucose into pyruvate. In the absence of oxygen, pyruvate is converted into lactate by the enzyme lactate dehydrogenase. This conversion regenerates NAD+, which is essential for the continuation of glycolysis.

Steps of Anaerobic Glycolysis

1. Glucose Uptake: Glucose is transported into the cell via glucose transporters. 2. Phosphorylation of Glucose: Glucose is phosphorylated to glucose-6-phosphate by the enzyme hexokinase. 3. Isomerization: Glucose-6-phosphate is converted to fructose-6-phosphate by phosphoglucose isomerase. 4. Second Phosphorylation: Fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate by phosphofructokinase. 5. Cleavage: Fructose-1,6-bisphosphate is split into two three-carbon molecules, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate, by aldolase. 6. Conversion: Dihydroxyacetone phosphate is converted to glyceraldehyde-3-phosphate by triose phosphate isomerase. 7. Oxidation and ATP Generation: Glyceraldehyde-3-phosphate is oxidized to 1,3-bisphosphoglycerate, generating NADH, and then converted to 3-phosphoglycerate, producing ATP. 8. Conversion to Pyruvate: 3-phosphoglycerate is converted to pyruvate through a series of steps. 9. Lactate Formation: Pyruvate is reduced to lactate by lactate dehydrogenase, regenerating NAD+.

Importance of Anaerobic Glycolysis

Anaerobic glycolysis is particularly important in muscle cells during intense exercise when oxygen supply is insufficient to meet energy demands. It allows for the rapid production of ATP, albeit less efficiently than aerobic respiration. The accumulation of lactate can lead to muscle fatigue and soreness.

Clinical Relevance

Anaerobic glycolysis is a key process in certain pathological conditions, such as cancer, where tumor cells often rely on glycolysis for energy production even in the presence of oxygen, a phenomenon known as the Warburg effect. Understanding anaerobic glycolysis is also important in the management of metabolic disorders and in the development of treatments for ischemic conditions.

Also see

• Aerobic glycolysis
• Lactic acid fermentation
• Metabolism
• ATP
• Warburg effect

Glucose

Hexokinase

ATP

ADP

Glucose 6-phosphate

Glucose-6-phosphate
isomerase

Fructose 6-phosphate

Phosphofructokinase-1

ATP

ADP

Fructose 1,6-bisphosphate

Fructose-bisphosphate
aldolase

Dihydroxyacetone phosphate

+

+

Glyceraldehyde 3-phosphate

Triosephosphate
isomerase

2 × Glyceraldehyde 3-phosphate

2 × 

Glyceraldehyde-3-phosphate
dehydrogenase

NAD⁺+ P_i

NADH + H⁺

NAD⁺+ P_i

NADH + H⁺

2 × 1,3-Bisphosphoglycerate

2 × 

Phosphoglycerate kinase

ADP

ATP

ADP

ATP

2 × 3-Phosphoglycerate

2 × 

Phosphoglycerate mutase

2 × 2-Phosphoglycerate

2 × 

Phosphopyruvate
hydratase (enolase)

 

H₂O

 

H₂O

2 × Phosphoenolpyruvate

2 × 

Pyruvate kinase

ADP

ATP

2 × Pyruvate

2 ×