Please Explain 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

Summary:

Glycolysis and the citric acid cycle produce relatively low amounts of ATP, but are essential in breaking down larger molecules such as glucose and other carbohydrates into electron carriers. Whereas, oxidative phosphorylation utilizes the transfer of electrons from the products of glycolysis and the citric acid cycle to produce larger amounts of ATP.

More detailed answer:

Oxidative phosphorylation can be difficult to understand at first due to the several intertwining processes. So, in order to better understand it, you will benefit from first solidifying your understanding of the products formed throughout glycolysis and the citric acid cycle. Simply put, the important products from both of these reactions are FADH₂ and NADH, secondary to their ability to undergo reduction/oxidation via transfer of electrons.

Oxidative phosphorylation is composed of two primary components. First, is the electron transport chain and second is chemiosmosis. During the electron transport chain, a series of proteins embedded in the inner mitochondrial membrane perform redox reactions. The FADH₂ and NADH from prior steps is the main source in which electrons are transferred, generating NAD⁺ and H⁺ ions. The NAD⁺ can be reused in other cellular steps and the H+ ions are moved to the other side of the membrane (the intermembrane space). It is important that the electrons are able to move through all proteins without trouble otherwise the process is doomed. The final step of the electron transport chain is the terminal acceptor (oxygen, which we breathe). In a functioning cell, this oxygen is essential in accepting the transferred electrons. Whereas, if you hold your breathe for a long time and do not take in enough oxygen, you may run out of terminal acceptors and your electron transport chain will be unable to proceed. As a result, your body would have to find an alternative pathway to produce energy, likely at a lower efficiency.

As a result of the electron transport chain, many H⁺ ions will build up in the intermembrane space and generate a proton gradient (higher concentration compared to the other side of the membrane). Chemiosmosis takes advantage of this, and transfers the H⁺ ions back into the matrix (the original side of the membrane). ATP is ultimately generated when these protons are brought back into the matrix. This happens via a proton pump which generates a proton-motive force. The proton pump ultimately harnesses the energy and charge difference from the protons to convert ADP and inorganic phosphate to ATP via ATP synthase. The more this pump rotates, the more ATP that will be produced. Thus, you can calculate how many ATP will be produced if you know how many NADH and FADH₂ entered the process. The result generates a large percentage of ATP within a system.