 The final part of respiration relies on the electron transport chain and I mentioned it happens across the mitochondrial inner membrane. Now I'm going to draw a few more pictures to explain how this works because the shape is really important for what it does. Here we have a mitochondria, the black part is its membrane, the purple part is its inner mitochondrial membrane. Lots and lots of folds. On the inside of that is the mitochondrial matrix which is kind of like an inner cytosol. And on the outside of the mitochondria itself is the cytosol, the juicy bits of the rest of the cell. Now I'm also going to draw in another part that we haven't mentioned which is the intermembrane space. This is the space between the mitochondrial membrane and the inner mitochondrial membrane and it's quite important for the electron transport chain. So to be more precise the electron transport chain occurs across the inner mitochondrial membrane and using the mitochondrial matrix and the intermembrane space. It's just more of a mouthful. If you haven't realised this already in biology, structure informs function and function informs structure. This wouldn't work if it wasn't this shape and if it wasn't this shape something else would have evolved. To show exactly what happens I've borrowed an image from the internet. So now we've zoomed in further and we're looking at the inner mitochondrial membrane. So this pink bit, just like the picture on the top, is the mitochondrial matrix. Orange will be the intermembrane space and the purple is our inner membrane. I'll colour these in more blue. These are called protein complexes. They're complex blobs of protein but we don't need to go too far into that. So their position within the membrane allows them to carry out some useful functions. Protein complexes do something where they couple a few jobs together. So on one hand they're transporting electrons that we've stored in NADH and FADH2 along the membrane eventually helping to create water, H2O there. At the same time, because this releases energy, they use that energy to transport the H+, the protons out of the mitochondrial matrix and into the membrane space. So the protein complexes are doing two things at once, which allows them to harness the energy that's released from the NADH for the next job. So what happens is that that intermembrane space gets filled with protons, with these hydrogen cations and this builds up a gradient. So there's more protons in the intermembrane space and less in the mitochondrial matrix. Now we talked about diffusion and osmosis before. When things are in high concentration in one area, they want to move to where there's a lower concentration to spread themselves out. So these protein complexes are pumping hydrogen ions away from where they naturally are and that's active transports pushing them into the intermembrane space. Now this last protein is another enzyme called ATP synthase. I wonder if you can guess what it does. ATP synthase is another membrane embedded protein, enzyme, that allows the proteins to come back through to where they want to be because of that gradient into the mitochondrial matrix. ATP synthase couples that movement because that's releasing energy. As they come back in, it uses that energy to combine ADP, adenosine diphosphate, with a phosphate to create ATP. This style of transport using osmosis of one thing to get something else done is called chemiosmosis. So at the end of the electron transport chain, if we follow just the path of one glucose molecule, this section produces 34 new ATP molecules.