Answer: You, like many other organisms, need oxygen to live. As you know if you’ve ever tried to hold your breath for too long, lack of oxygen can make you feel dizzy or even black out, and prolonged lack of oxygen can even cause death. But have you ever wondered why that’s the case, or what exactly your body does with all that oxygen?
As it turns out, the reason you need oxygen is so your cells can use this molecule during oxidative phosphorylation, the final stage of cellular respiration. Oxidative phosphorylation is made up of two closely connected components: the electron transport chain and chemiosmosis. In the electron transport chain, electrons are passed from one molecule to another, and energy released in these electron transfers is used to form an electrochemical gradient. In chemiosmosis, the energy stored in the gradient is used to make ATP.
So, where does oxygen fit into this picture? Oxygen sits at the end of the electron transport chain, where it accepts electrons and picks up protons to form water. If oxygen isn’t there to accept electrons (for instance, because a person is not breathing in enough oxygen), the electron transport chain will stop running, and ATP will no longer be produced by chemiosmosis. Without enough ATP, cells can’t carry out the reactions they need to function, and, after a long enough period of time, may even die.
In this article, we'll examine oxidative phosphorylation in depth, seeing how it provides most of the ready chemical energy (ATP) used by the cells in your body.
Overview: oxidative phosphorylation
Simple diagram of the electron transport chain. The electron transport chain is a series of proteins embedded in the inner mitochondrial membrane. In the matrix, NADH and FADH2 deposit their electrons in the chain (at the first and second complexes of the chain, respectively). The energetically "downhill" movement of electrons through the chain causes pumping of protons into the intermembrane space by the first, third, and fourth complexes. Finally, the electrons are passed to oxygen, which accepts them along with protons to form water. The proton gradient produced by proton pumping during the electron transport chain is used to synthesize ATP. Protons flow down their concentration gradient into the matrix through the membrane protein ATP synthase, causing it to spin (like a water wheel) and catalyze conversion of ADP to ATP.
Simple diagram of the electron transport chain. The electron transport chain is a series of proteins embedded in the inner mitochondrial membrane.
In the matrix, NADH and FADH2 deposit their electrons in the chain (at the first and second complexes of the chain, respectively).
The energetically "downhill" movement of electrons through the chain causes pumping of protons into the intermembrane space by the first, third, and fourth complexes.
Finally, the electrons are passed to oxygen, which accepts them along with protons to form water.
The proton gradient produced by proton pumping during the electron transport chain is used to synthesize ATP. Protons flow down their concentration gradient into the matrix through the membrane protein ATP synthase, causing it to spin (like a water wheel) and catalyze conversion of ADP to ATP.
Step-by-step explanation:
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