The glucose alanine cycle vs cori cycle. What’s the difference between the two? How do they effect your body? Which one’s better at providing you with energy for working tissues? Well, in this article we’ll discover the answer to these questions and will help give you a better understanding of these two very important metabolic pathways. So, let’s find out which pathway beats out the other in the Glucose Alanine Cycle VS Cori Cycle face-off!
So, what is the glucose alanine cycle?
The glucose alanine cycle is a vital metabolic pathway that allows the body to obtain energy from protein. This usually occurs when the body is in “survival mode” in an attempt to conserve fatty acids like triglycerides. More specifically, it works by converting amino acids into glucose. This conversion of protein to carbohydrates may not seem logically possible, but as you will shortly see, several key substrate reactions allow this to be so.
The glucose alanine cycle starts off by having muscle glycogen (in glycogenolysis) or blood glucose (in glycolysis) breakdown into its concluding constituent substrate: Pyruvate (aka pyruvic acid). As this happens, a protein molecule breaks down into its amino acid constituents: Leucine, Isoleucine, and Valine, among others.
The amino acid’s carboxyl group (COOH) and its amino acid side chain (from the foregoing protein molecule) goes to the Krebs Cycle and to the Electron Transport Chain to be converted into other substrates to eventually make ATP (among other substrates).
There is also the amino group (NH2) that I’m leaving out. This is what will trigger the glucose alanine cycle to initiate it’s unique set of reactions.
This works by having the NH2 from the protein molecule combine with pyruvate (the last substrate in glycolysis). When this happens, they create the substrate Alanine (Pyruvate + NH2 > Alanine). This is known as transamination. Alanine then travels from the muscle cell through the blood, eventually reaching the liver. Once alanine is in the liver, the amino group NH2 is removed from it and converted into urea. This is known as deamination.
Once deamination occurs, alanine then gets converted into glucose/liver glycogen through a process called gluconeogenesis. It’s basically the reverse of glycolysis. So, through gluconeogenesis in the glucose alanine cycle, alanine (a substrate of a protein reaction) gets converted into glucose.
This glucose then either gets converted into liver glycogen or flows through the blood back toward the muscle. Here it can be converted into muscle glycogen or it can repeat the entire process again. Thus, why its called the glucose alanine cycle.
How does the cori cycle work?
The cori cycle works by converting lactic acid into glucose. It’s much more simple (especially to explain) than the glucose alanine cycle is. It begins with (fast) glycolysis. Pyruvate is converted into lactic acid. In an attempt for your body to generate more energy, it has lactic acid flow through the blood to the liver. Once lactic acid reaches the liver it goes through a process that’s called glucogenesis. This is the reverse of glycolysis. So, lactic acid then gets converted into glucose or can be stored as liver glycogen.
The glucose then flows through the blood back to the skeletal muscle to repeat the process via glycolysis/glycogenolysis. Thus, why it’s called the cori cycle.
Glucose alanine cycle VS Cori cycle Main Differences
The most substantial piece of information to take away here, besides what each cycle produces is when they produce it. The glucose alanine cycle generates glucose from a protein molecule when the body is in a “starvation” state. This survival status quo is what allows the glucose alanine cycle to commence in the first place.
The cori cycle is used during much less critical conditions. This cycle takes place during fast glycolysis or during a high intensity fartlek training session where excess lactic acid would be accumulated. In an attempt to rid the body of acidic lactate, the cori cycle is then implemented.
Final thoughts on the glucose alanine cycle vs cori cycle
Both the glucose alanine cycle and the cori cycle are both vital metabolic pathways that allow the body to keep pushing forward during strenuous conditions. The glucose alanine cycle is called upon during extreme conditions like a marathon or if someone has been fasting for a long period of time.
The glucose alanine cycle can even be called upon if someone is doing a no-carb diet or a very low-carb diet while exercising strenuously. The body needs energy from somewhere. So, if it can’t get it from carbs due to a lack thereof, then it can get it from protein (to conserve the more energy important adipose tissue).
The cori cycle can be called upon during tabata training, HIIT, plyometrics, fartlek training, ViPR training, bodybuilding, sprinting, ect. Basically any type of exercise that would accumulate excessive lactic acid for a significant duration. Lactic acid has a purpose.
It isn’t just there to make your muscles hurt more. Among many of its functions, it sits at the cornerstone of the cori cycle. Having the ability to convert lactic acid into glucose via glucogenesis allows you to feel less fatigued and more energized.