Oxidative Phosphorylation

Question

Hi I'm a college student studying microbiology. Right now I'm studying the way animal cells make ATP through the Mitochondrion. there are three things that have to take place for ATP to be created Glycolysis, the Citric Acid Cycle, and Oxidative Phosphorylation. I have some understanding of glycolysis in that it takes glucose and makes pyruvate. A little less understanding of the Citric Acid cycle, all I understand is that it makes some NADH and ADP. And zero understanding of how Oxidative Phosphorylation works. Can you please explain oxidative Phosphorylation to me. Thank you

Answer 1

Dear Lilliam,

Below I share some lines in regards to your question.

Oxidative phosphorylation is the final stage of cellular respiration and occurs within the mitochondria of eukaryotic cells. Its primary purpose is to produce adenosine triphosphate (ATP), the cell's primary energy currency. Here's a simplified breakdown of how oxidative phosphorylation works:

1. Electron Transport Chain (ETC): Oxidative phosphorylation takes place in the inner mitochondrial membrane, specifically in a group of protein complexes known as the electron transport chain (ETC). The ETC consists of four protein complexes (Complex I, II, III, and IV) and a special molecule called coenzyme Q and cytochrome c.

2. Electron Transfer: During the earlier stages of cellular respiration (glycolysis and the citric acid cycle), high-energy electrons are extracted from glucose and transferred to carrier molecules like NADH and FADH2. These high-energy electrons are now shuttled to the ETC.

3. Electron Flow: The electrons are passed through the ETC from one protein complex to another, in a series of redox reactions. As electrons move through the chain, they gradually lose energy.

4. Proton Pumping: As electrons move through the ETC, hydrogen ions (protons) are pumped across the inner mitochondrial membrane from the mitochondrial matrix into the intermembrane space. This creates a concentration gradient of protons, with more protons in the intermembrane space than in the matrix.

5. ATP Synthase: In the inner mitochondrial membrane, there's a protein complex called ATP synthase. It acts as a molecular turbine, using the energy generated by the flow of protons (through ATP synthase) back into the mitochondrial matrix to convert adenosine diphosphate (ADP) and inorganic phosphate (Pi) into ATP.

6. ATP Production: The flow of protons through ATP synthase provides the energy needed for ATP synthase to combine ADP and Pi to form ATP. This process is often referred to as chemiosmotic coupling.

So, in summary, oxidative phosphorylation uses the energy released during the transfer of electrons through the electron transport chain and the subsequent pumping of protons to generate ATP. This process is highly efficient and is responsible for the majority of ATP production in animal cells, making it a crucial component of cellular energy metabolism.

Feel free to reach out if other questions about carbohydrate metabolism and cellular energy mechanisms.