Cellular Respiration: Krebs Cycle and Electron Transport Chain

Step 3: Krebs Cycle

The Krebs Cycle is also known as the Citric Acid Cycle and occurs in the matrix of the mitochondria. The Krebs Cycle is a chemical reaction being used by aerobic organisms in order to create energy by oxidizing the acetate into carbon dioxide. 

In the Krebs Cycle, there is the product from the Pyruvate Oxidation which is Acetyl CoA which enters the Krebs cycle by combining with four carbon acids which form Citrate. NAD+ converts to NADH + CO2 meaning that the carbon lost is CO2. NAD+ converts to NADH + CO2 again and the next step in the Krebs cycle is GDP, Pi which then converts to GTP. GTP is an energy-carrying molecule that is similar to ATP. Then FAD converts to FADH2. NAD+ is then reduced to NADH. After that, there are four carbon acceptor molecules that are regenerated in every cycle. Like that the cycle repeats. The products of the Krebs Cycle are 2 ATP, 4 CO2, 6 NADH and 2 FADH2. 

Step 4: Electron Transport Chain (ETC)  

The Electron Transport Chain aka ETC occurs in the inner membrane of the mitochondria. Electron Transport Chain is electron transporters that are set in the inner membrane of the mitochondria. Electrons that are excited in the Krebs cycle reaction are carried by NADH and FADH2 to the electron transport chain. 

First, an NADH molecule is at the Protein Complex 1 and complex 1 then receives two electrons from NADH oxidizing it to NAD+. One Hydrogen is then sent into the intermembrane space for every electron. Then FADH2 is oxidized to FAD. The electrons in complex 1 then move to the next and next complex until the fourth complex which then releases O2 and converts to H2O. There is a proton gradient created in the electron transport chain. A proton gradient is the product of the electron transport chain where there is a higher concentration of proton outside of the inner membrane in the intermembrane space and a low concentration of protons inside the inner membrane in the matrix. Since there is a high concentration of H+ in the intermembrane space, the H+ would go through ATP synthase and ADP would convert into ATP. The purpose of the electron transport chain is to produce ATP. Also, the electron transport chain pumps H+ into the intermembrane space resulting in a high concentration of H+ which would allow there to be a production of ATP. In the end, the electron transport chain would produce NAD+, FAD, water and ATP.

The Krebs Cycle and the Electron Transport Chain are very important stages to cellular Respiration in plants because the Krebs Cycle is needed so that the electrons in the Krebs cycle can be carried to the electron transport chain. The Electron transport chain is important as well because without the electron transport chain then ATP wouldn’t have been able to be produced. In order to produce ATP, there needs to be an electron transport chain. In the end, in order for cellular Respiration to work then, four stages of cellular Respiration are needed which are Glycolysis, Pyruvate Oxidation, Krebs Cycle and Electron Transport Chain.