I Bleed

This picture will actually make sense (hopefully), by the time you get to the end, you might even be able to spot some deep specifics down in this mess. Watch it move here

So, since I'm learning some amazingly cool things in some of my classes, I just gotta share them with you. But we'll need some background and defs:
Amino Acid: Basically you got a Nitrogen (N) and he likes extra loose Hyrdrogen ions (H+), then attach a Carbon (C), and another Carbon with two Oxygens (O) attached to it. One Oxygen has an H, but he no likey hang onto it, so the Nitrogen snags it (at the pH within your body). So N has a + charge, and O has a - charge. Then you link these amino acids from end to end (the Nitrogen replaces one of the O's which leaves with a few H's and you got water coming off, H2o). On the middle Carbon is one H and a thingy called an R-Group, and these are of all different varieties, some are + charged, some - charged, some neutral (they hate being around charges of any kind) and a few in between. (the N groups are called aminos, and the C with two O's group is an acid --since it drops the H+ off pretty readily, Oxygens like to be negative, and Hydrogens are generally happy, or positive--thus you call them "amino acids".
Protein:Put a bunch of Amino Acids together end-to-end and you got a Protein. Depending on the R-groups and the order of AA's. The proteins take on different shapes. The blobular proteins have various pockets and spots on them that do things, like stick to other proteins or expand and contract depending on pH (which is how many extra H+'s you got floating around). This shape shifting and sticking is how enzymes work and most of what your body is doing.
Hemoglobin Molecule: A blob of 4 globular proteins stuck together, two identical alpha hemoglobins and two identical beta hemoglobins. Each has a spot where a funky porphyrin ring sits. This ring is usually flat and has a single atom of charged iron floating in the middle. The iron is missing two of its electrons so it has a +2 charge, and it shares electrons with the N's on the ring. So it's pinned on four sides by the N's in the ring. Nearby underneath it, is a Histidine Amino Acid (similar to Histamine), with a couple N's on it's pentagon-style R-group, so it can hold the iron in place from one side. On the remaining open side is where a molecule of oxygen (two O's stuck together) sits.
Ions: Ions are atoms that either have extra or missing electrons floating around their outsides. So they take on charges. Chlorine absolutely LOVES having extras, its greedy like that. That's why neutral chlorine gas is so dangerous. 2 Chlorines stuck together having to share their electrons with each other. FORGET THAT!! They'll rob them from anywhere to take on an extra and get a negative charge and say splitsville to the other chlorine. Sodium metal is EXPLOSIVE in water, because it HATES having a neutral charge too. It wants to ditch one somehow. Sodium is more than happy to give one up to chlorine, and chlorine is happy to take it. Thus they are both happy and still stick around each other for good company totally inert to doing anything else (this is table salt). Similarly, iodine and fluorine are dangerous, but iodide (-1) (like in disinfectants) and flouride (-1) like in toothpastes are not so bad. Even calcium metal, like sodium, is pretty terrible, but the calcium ion that makes your teeth and bones, is very good. (Fluoride and calcium combine into tiny crystals that are much more resilient to acid and bacteria to protect your enamel, just don't go swallowing tons of fluoridated toothpaste) Lots of these things dissolve in water because the oxygen carries most of the negative charge, and the H's, most of the positive charge, thus they pull apart ionic molecules, sharing the charges all around (Drinks for Everybody!) in a big crowded party.
Osmosis and Diffusion: They are different, but similar principles. Basically, where there's not a lot of something, more will flow into it. Where there's no air, air goes. Where there's lots of Oxygen and little Carbon dioxide, oxygen leaves and carbon dioxide comes, until there's equal amounts of everything everywhere.

If you've made it this far, congratulations are in order for everyone: to the reader for staying attentive, and me, for writing so that other people can understand.

Back to Hemoglobin and Blood. So you have a red blood cell that looks like a flattened basketball and it's been stripped of normal cell things and is mostly just a sack full of hemoglobin blobs-- more blobs than you could count in each cell. There's some flex in the the whole 4-part blob. It's not steel or anything, it can jiggle depending on the conditions surrounding it. The presence of Oxygen on the ring site changes the shape a bit. When there's no oxygen, it's called the Tense or T-State, because that porphyrin ring is tweaked-bent a bit and it doesn't like that. But there's some help holding such a shape from other amino acids in the blob that all of a sudden are close enough to like each other a bit more and hook-up. The tense state actually doesn't like to hold oxygen as well and if it's full of oxygen (all four rings in the blob), it will dump them off. If it's semi-full it will take more or less depending on how much oxygen is in the vicinity. When partly full of oxygen and no reason to be tense, it will take all it can get. What makes hemoglobin tense? Acid. Extra H+'s. Where does this come from? The mixture of CO2 and H20 (carbon dioxide and water). When CO2, which is being cranked out by working cells (especially muscle cells), it dissolves in water: it grabs the O in water and reforms itself (sometimes with help from enzymes and other things) to make Carbonic Acid or H2CO3. It doesn't like the extra tag-along H+, so it drops it like a rock. There you have a negatively charged bicarbonate HCO3- (sodium Na+ with bicarbonate HCO3- is sodium bicarbonate, Baking Soda) and some of it decides to leave the blood cell. Well, blood cells on the whole don't like to have charge (except nerve cells) so a chloride ion comes into the party from outside the cell (there's tons of it in your blood, fluids, and everywhere). The chloride attaches to the hemoglobin at a specific spot, FURTHER stabilizing the tense state.

Lets put the whole thing together and watch a blood cell flow through your veins. Start off with it full of Oxygen. Prepped up and ready to go. It leaves your lungs (where there's lots of oxygen) and goes through your arteries, and down to your tissues, like muscle tissue. It gets there and "WHOA, what's all this carbonic acid doing here, oh no, the H+'s and Chloride Cl-'s are making me change shape and dump out all my Oxygens!! Oh man! Now I'm stuck in this lame party carrying all this dead weight extra HCO3-, H+, and Cl-, and all I wanted was my good friend Oxygen." A short while later, it gets back to your lungs, and "Hey, lots of Oxygen, and not a lot of Carbon Dioxide! Look! The HCO3- and H+'s pop back into water and carbon dioxide so that new carbon dioxide molecules can go populate the atmosphere!!" And with them gone, the oxygen flows in smoothly.

Thus, in this manner, blood drops off oxygen where it's most needed and not where it's not needed. Way cool, isn't it?!?!? What's DOUBLY SUPER amazing is that somewhere in your tons of DNA is a specific set of nucleotides arranged in the right order, to make a "code", so that when amino acids match up with the code, it spells out the right order of amino acids that they clump up into a blob the way they like and act just like hemoglobin! Why, it would be hemoglobin! How'd the code get formed?? That's a long story and took 4 billion years or so. Or at least 7 creative periods or days, whichever you prefer.