What is the Difference Between Cori Cycle and Glucose-Alanine Cycle

The main difference between Cori cycle and glucose-alanine cycle is that the Cori cycle transports lactate and glucose between the liver and muscle under anaerobic conditions, whereas the glucose-alanine cycle transports alanine between the liver and muscle.

The Cori cycle and glucose-alanine cycle are two reactions between the liver and skeletal muscles. 

Key Areas Covered

1. What is Cori Cycle (Lactic Acid Cycle)
– Definition, Process, Importance
2. What is Glucose-Alanine Cycle (Cahill Cycle)
– Definition, Process, Importance
3. Similarities Between Cori Cycle and Glucose-Alanine Cycle
– Outline of Common Features
4. Difference Between Cori Cycle and Glucose-Alanine Cycle
– Comparison of Key Differences

Key Terms 

Alanine Cycle, Cori Cycle, Cahill Cycle, Glucose-Alanine Cycle, Lactic Acid Cycle

What is Cori Cycle

The Cori cycle or lactic acid cycle is a cycle that occurs between the liver and the skeletal muscles, converting glucose into pyruvate and then into lactate. Carl Ferdinand Cori and Gerty Cori discovered it. Here, anaerobic glycolysis produces lactate in skeletal muscles that is again converted into glucose in the liver. Also, skeletal muscles require ATP for muscular activities, and the breakdown of glycogen or glycogenolysis produces them. It releases glucose in the form of glucose 1-phosphate that undergo glycolysis, citric acid cycle, and oxidative phosphorylation to produce ATP under aerobic conditions.

Figure 1: Cori Cycle

Furthermore, under anaerobic conditions, such as intense muscular activity, lactic acid fermentation occurs inside the skeletal muscles that convert pyruvate into lactate. Lactate dehydrogenase is the enzyme responsible for the formation of lactic acid. The liver takes up lactate to process gluconeogenesis, which is the reverse reaction of glycolysis. It converts lactate into pyruvate and back to glucose. Therefore, the Cori cycle occurs under anaerobic conditions, converting back lactate into glucose inside the liver. 

What is Glucose-Alanine Cycle

Glucose-alanine cycle, alanine cycle, or Cahill cycle is another cycle that occurs between the liver and skeletal muscles. It involves the transport of carbon and amino groups into the liver. In the energy requirements of muscles, proteins in the muscles degrade into amino acids. The resulting nitrogen undergoes transamination to form pyruvate that is converted into alanine. Alanine transaminase is the enzyme that converts pyruvate into alanine. Alanine enters the liver to undergo the urea cycle. The resulting pyruvate is used in gluconeogenesis in the liver to produce glucose.

Figure 2: Glucose-Alanine Cycle

Moreover, the glucose-alanine cycle is less productive than the Cori cycle. Also, it produces a lesser number of ATP than the Cori cycle. 

Similarities Between Cori Cycle and Glucose-Alanine Cycle

• The Cori cycle and glucose-alanine cycle are two cycles that exchange nutrients between the liver and skeletal muscles.
• Both cycles operate under anaerobic conditions.

Difference Between Cori Cycle and Glucose-Alanine Cycle 

Definition

The Cori cycle is a metabolic route in which lactate created by anaerobic glycolysis in muscles is transported to the liver and transformed into glucose. In contrast, the glucose-alanine cycle is an interorgan metabolic pathway between muscle cells and the liver.

Significance

The Cori cycle transports lactate and glucose between the liver and muscle under anaerobic conditions, while the glucose-alanine cycle transports alanine between the liver and muscle.

Importance

The Cori cycle is essential for energy production under aerobic conditions, while the glucose-alanine cycle is vital for removing nitrogen from the body. 

Net ATP Production

Net ATP production is high in the Cori cycle, while net ATP production is low in the glucose-alanine cycle.

Productivity

The Cori cycle has high productivity, while the glucose-alanine cycle has low productivity.

Conclusion

In brief, the Cori cycle and glucose-alanine cycle are two cycles that operate in the body. They occur between skeletal muscles and the liver. The Cori cycle operates under anaerobic conditions transporting lactate and glucose between the liver and skeletal muscles. It is essential for energy production under anaerobic conditions. In comparison, alanine is transported between the liver and the skeletal muscles in the glucose-alanine cycle. It is important for the removal of nitrogen from the body. Therefore, their importance is the main difference between Cori cycle and glucose-alanine cycle.

References:

1. Cori cycle. Cori Cycle – an overview | ScienceDirect Topics. (n.d.). 
2. S. National Library of Medicine. (n.d.). Glucose-alanine cycle. National Center for Biotechnology Information. PubChem Compound Database. 

Image Courtesy:

1. “Cori Cycle” By user:PDH – Own work (CC-BY SA 3.0) via Commons Wikimedia
2. “Cori & Alanine Cycle edited by wrekodara” By Arya Bima – Own Work (CC-BY SA 3.0) via Commons Wikimedia