All of the steps of aerobic respiration that we have done so far have been leading up to this, the electron transport chain. This is the main event, the big bonanza, the Super Bowl of cellular respiration. Why?
Because the vast majority of our ATP is made here. The electron transport chain is actually a series of proteins and other molecules embedded in the inner membrane of the mitochondrion. These molecules transport electrons, hence the name. Let's zoom in on this inner membrane to see the electron transport chain in more detail.
Here's how it works. NADH, that electron carrier we've been making all along, delivers its electrons to the first protein in the electron transport chain. As the electrons move through this protein complex, energy is gradually released, and this energy is used to pump hydrogen ions, or protons, across the inner membrane from the matrix into the intermembrane space. At this point, it might help to realize that moving electrons is electricity.
So it should not be surprising that these electrons can provide the energy to drive these microscopic pumps made out of protein. They are basically natural electric pumps, created way before... humans invented them, which is super cool.
The electrons are then transported by this special red molecule toward their next destination. The red molecule also picks up the electrons donated by FADH2, that other electron carrier that we made during the Krebs cycle. All of these electrons are then passed on to another protein complex. At this next protein complex, the electron energy is used once again to transport hydrogen ions across the membrane into the intermembrane space. Notice that we are building up a high concentration of hydrogen ions in the intermembrane space.
This will be very important soon. Now the electrons are transported to a final protein complex where their energy is used once again to pump hydrogen ions into the intermembrane space making the concentration even higher. Now the electrons need somewhere to go a final destination to complete their journey. Fortunately, you breathe, and oxygen comes to the rescue. Oxygen accepts the electrons, as well as hydrogens from the matrix, making water.
This is the reason why you breathe all day, every day. Your cells need oxygen to accept these electrons, or the electron transport chain will grind to a halt, like an LA freeway during rush hour. And if the electron transport chain stops, you won't be able to make enough oxygen. ATP to keep you alive and you die.
So keep breathing that oxygen. Now you may have noticed that we haven't made ATP yet, so you might be wondering how that works, which brings up the coolest part of this entire process in my opinion. Remember that high concentration of hydrogen ions we've been building up?
Now it's time to use it to make ATP. A protein called ATP synthase makes a channel that allows hydrogen ions to flow through from high concentration to low concentration. You may remember that molecules tend to move from areas of high concentration to low concentration. naturally, a process known as diffusion.
So these hydrogen ions, in a manner of speaking, want to flow from the high concentration area of the intermembrane space to the low concentration area, the matrix. But they can only get through ATP synthase. This facilitated diffusion of hydrogen ions through ATP synthase causes ATP synthase to spin like a turbine and produce ATP.
Such a cool mechanism. It's like a microscopic hydroelectric dam, generating ATP instead of electricity as hydrogen ions passively flow through. Since we made many electron carriers throughout respiration, the electron transport chain happens over and over again, making between 30 to 34 ATP molecules for every glucose that entered respiration.
If you are doing the respiration activity at Bioman Biology, you should now return to it and complete the tasks related to the electron transport chain. The link to the respiration activity is in the description in case you need it. If you enjoyed this video, please like it, subscribe, and check out the other free games, quizzes, and interactive learning experiences at Bioman Biology.