Krebs Cycle vs Electron Transport Chain: Comparative Analysis

This article would highlight the details regarding Krebs Cycle vs Electron Transport Chain, where both the processes occur in mitochondria.

Cellular respiration is described as a catabolic process where various respiratory substrates such as glucose are oxidised to produce carbon dioxide along with water and ATP as energy. In this cellular respiration, Krebs cycle and Electron Transport Chain (ETC) are the two very significant stages. 

Krebs Cycle vs Electron Transport Chain

The table below would identify the differences between the two processes: 

Krebs cycle 

The Krebs cycle, also known as Citric acid cycle or Tricarboxylic acid cycle is a part of the cellular respiration process where organic fuel molecules like glucose, amino acids, fatty acids are broken down to primarily produce ATP as energy and carbon dioxide along with other constituents as by-products. In the process of glycolysis, two pyruvate molecules are formed by breaking down glucose which are then converted to Acetyl CoA within mitochondria to enter the Krebs cycle. Here the Acetyl CoA combines with oxaloacetate to produce citrate and lastly produce ATP and Carbon dioxide. 

Electron transport chain

The reduced carriers NADH and FADH2 being produced within the Krebs cycle further enters the ETC and then the electrons from the molecules are passed from one member to the other within the ETC through a series of redox reactions. The electrons move from a higher energy level to a lower energy level which leads to the release of energy.  The energy being released from these sets of reactions lead to a proton gradient moving from the matrix to the intermembrane space which further leads to the generation of ATP through the process of chemiosmosis using the enzyme ATP synthase. 

Relationship between Krebs cycle and Electron Transport Chain

In the process of cellular respiration, the breaking down of glucose molecules occurs to produce carbon dioxide and water. Along the entire process, production of ATP occurs which helps in transforming glucose and in the last stage called oxidative phosphorylation, a large amount of ATP is formed through the ETC.

In the first step of cellular respiration, a six-carbon compound, glucose undergoes several chemical transformations to produce two molecules of three-carbon organic molecules called pyruvate. In the next step, pyruvate oxidation occurs within the mitochondrial matrix which forms a two-carbon molecule called Coenzyme A, also known as Acetyl CoA. The next step is the Krebs cycle where Acetyl CoA combines with oxaloacetate to regenerate the starting molecule and release NADH, ATP and FADH2 along with Carbon dioxide.

These molecules NADH and FADH2 released in the Krebs cycle tend to deposit the electrons within the ETC in order to return back to their empty forms. As the electrons flow down the chain, energy is being released to form a proton gradient pump to form ATP in the presence ATP synthase. Thus, the Electron Transport Chain is dependent on the Krebs Cycle as the products that are released through the cycle, which are NADH and FADH2 are used in the transport chain. 

Read more on: Is Krebs Cycle Part Of Photosynthesis: Why, How

Krebs cycle and electron transport chain similarities

In terms of identifying the similarities, it can be identified that both Krebs cycle and electron transport chain forms two very significant parts of the cellular respiration process. Both the processes occur in every aerobic living organism in order to survive. The site of occurrence is also the same where the Krebs cycle and electron transport chain occur within the mitochondria of the cells. Krebs cycle occurs in the matrix of the mitochondria whereas the ETC occurs within the inner membrane of mitochondria.

Both the processes engage in releasing ATP but Krebs cycle releases only 2 ATPs whereas ETC releases 34 ATPs. The products that are released through the Krebs cycle are used within ETC, which are NADH and FADH2. These two molecules release electrons to move past the electron chain in order to produce a large amount of ATP as energy. 

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