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Electron Transport Chain: Stage 3 of Cellular Respiration

Electron Transport Chain: Stage 3 of Cellular Respiration

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This lesson will describe in detail the processes that occur in the ETC phase of cellular respiration.

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Tutorial

The Electron Transport Chain

Source: Video and Images Created by Amanda Soderlind

Video Transcription

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In this lesson, we are going to discuss the processes that occur in the electron transport chain as a phase of cellular respiration.

So cellular respiration, if you'll remember, is the process in which cells make ATP-- or adenosine triphosphate-- which is energy for themselves. And the electron transport chain is that third and final step of cellular respiration, and it occurs in the inner membrane of the mitochondria. So if you take a look at this little diagram right here, we have the mitochondria, and we have, in blue, highlighted the electron transport chain. So it's happening in that inner membrane of the mitochondria.

And the stages that come before it are glycolysis and Krebs cycle. So you can see, by the arrows here, that products from each of these processes are transferred into the next step. So we have some products from glycolysis being transferred into the electron transport chain, and we have some products from the Krebs cycle also being transferred into the electron transport chain. So the chains of reaction that happen use energy released by electrons to produce ATP.

So the vast majority of ATP is being produced in this third step, and that energy's being produced by electrons, by energy that's released by electrons. And each chain of reactions that occurs is called an electron transport system. So let's take a look in depth at what's happening during this phase. And I'm going to zoom in here, just so you can see a little bit more clearly. OK.

So as I had mentioned earlier, we have products from glycolysis and from the Krebs cycle that will enter into our electron transport chain. So those products are right here. And these are those electron carrier molecules. So electrons that were picked up during glycolysis or the Krebs cycle are transferred to the electron transport chain. So this little purple ball here is going to represent our electron. So these were carrying electrons from prior steps to the electron transport chain.

So hydrogen-- our H-plus here is representing a hydrogen molecule. So hydrogen picked up by molecules in the inner membrane are released to the outer membrane when they pick up and donate electrons. So molecules that are in our inner membrane-- so our inner membrane is in here, and our outer membrane of our mitochondria is here. Remember, a mitochondrion has two membranes, our inner and outer.

OK so molecules, when they pick up an electron, will also pick up the hydrogen. And that hydrogen will move from the inner membrane to the outer membrane. And that electron will then move on to somewhere else. So basically what's going to happen is we're going to have a bunch of hydrogens picked up by molecules and moved to the outer membrane. And it's going to produce this gradient in the outer membrane of hydrogens.

And then what's going to happen is if we have this buildup of hydrogens, if we have this gradient in the outer membrane, those hydrogens are naturally then going to start to flow back into the inner membrane to even out that concentration. And so they're going to flow through enzymes. Oops, let me zoom out. Sorry, you can't see that very well. That was my fault. OK.

So they're going to flow through these enzymes. And basically these enzymes will catalyze the formation of ATP from ADP and phosphate. So we'll have AD molecules which will then gain a phosphate and turn into ATP as the hydrogen moves through this enzyme. So we have the production of ATP, which is energy.

And also what is going to occur is that we're going to have oxygen-- oxygen molecules outside of the mitochondria, and they're going to fuse with hydrogen molecules to form H2O. So this electron is giving the hydrogen and oxygen energy in order to be able to bond and form H2O, which is water. OK?

So in this process, we are actually forming 32 molecules of ATP, which is quite a few. If you'll remember back to glycolysis and the Krebs cycle, each of those is only forming two molecules of ATP. So this is forming the vast majority of ATP formed by cellular respiration. So in total, if we add the ATP from glycolysis and from the Krebs cycle, we would have a net total of 36 ATP produced by the end of cellular respiration.

So this lesson has been a brief overview on the process of the electron transport chain as the third and final step of cellular respiration.

TERMS TO KNOW
  • Electron Transport Chain

    The third and final phase of cellular respiration in which electrons are used to produce 32 molecules of ATP.