Introduction to Krebs cycle biology animation

Another challenge for our Medical Animation Studio was to create a detailed overview of the inner compartment of the mitochondrion, where the Krebs cycle biology animation occurs. This is a glimpse of the original animation.

How important is the Krebs cycle in our body?

The citric acid cycle plays a major metabolic role in our bodies. Along with supplying energy, this cycle also provides the intermediates needed for the synthesis of compounds like glucose, amino acids, etc. 

Its importance is proved by giving it three different official names. The first name, the citric acid cycle (CAC), refers to the first molecule that forms during the cycle’s reactions — citrate, or, in its protonated form, citric acid. Tricarboxylic acid (TCA) cycle is also widely used based on the three carboxyl groups on its first two intermediates, and the Krebs cycle, which is named after its discoverer, Hans Krebs.

A bit of history

A German-born British physician and biochemist Sir Hans Adolf Krebs submitted a series of reactions in 1937, which he stated as the citric acid cycle. In 1953, he was awarded the Nobel Prize in the field of Physiology or Medicine for this contribution. Although Krebs explained most of the reactions of the cycle, there were some reactions missing in his works. The gaps were filled by Fritz Lipmann and Nathan Kaplan, who discovered the coenzyme A (CoA) in 1945 which allowed scientists to determine the pathway of reactions as it is known today.

The functions of the citric acid cycle

Whatever you prefer calling it, this cycle is the primary driver of cellular respiration. In eukaryotic cells, the CAC takes place in the matrix of the mitochondrion. As a cycle, it is a closed loop; the last part of which reforms the molecule used in the first step. The TCA cycle plays a crucial role in the catabolism (breakdown) of the organic fuel molecules: glucose and other sugars, fatty acids, and some amino acids. These large molecules must be degraded into a two-carbon compound called acetyl coenzyme A (acetyl CoA) before they enter the Krebs cycle. Acetyl CoA is converted into carbon dioxide and energy after it gets into the citric acid cycle.

What is the Krebs cycle?

CAC is a pathway of chemical reactions that are present in all aerobic organisms. This series of reactions is dedicated to releasing stored energy by the oxidation of acetyl-CoA obtained from fats, carbohydrates, and proteins into carbon dioxide and adenosine triphosphate (ATP). In addition, the cycle provides precursors of certain amino acids, as well as NADH (a reducing agent), that is used in various other biochemical reactions. Even though it is called a ‘cycle’, it is not necessary for the metabolites to follow just one specific route.