we're in part two now page 34 and we're beginning in this chapter on chemistry and biochemistry some ideas about the molecules of life and I would like to present you with these two molecules actually are of considerable interest to us because when we metabolize food for energy we're going to end up with co2 and water the complete combustion of a carbohydrate such as glucose or starches which are collections of glucose molecules will end up when they aren't completely oxidized the end product will be carbon as carbon dioxide and then we're going to be collecting hydrogen with an oxygen molecule and we're going to end up with water this would be the water of metabolism so to speak that at any rate water is also a solvent in which many of the reactions of life are happening and it's this polar molecule that's of interest to us so the hydrogen is a very very small atom and has only one electron that it loses in the presence of oxygen went covalently bound and we have this more or less shape of a molecule oxygen has the much larger atomic number than hydrogen which is only a 1 so something in the order of 16 to 1 and so oxygen actually is much larger than is being depicted here but in anyway we get the idea that a water molecule is polar and this is a partial negative charge over here it's a little bit hard to make out partial negative and this is a partial positive charge over here and this has consequences for us and so with this idea we're going to come over into this picture here on the next page page 35 and we're going to consider the idea of hydrogen bonding and so in physical chemistry there are the ideas of clathrates or momentary crystals in which the molecules when they're able to freely freely move in a in solution are able to readjust themselves into these momentary weak bond positions and they they take up these positions with a certain degree of force when they're considered in the collective and the force is represented by surface tension and you can see that there are species that are light enough and able to distribute their mass well enough that they can literally take a little walk on the water water therefore has shall we say equality that is not exactly what and I want to further demonstrate that the idea of if you're a child shooting an arrow at your mother's refrigerator and it has a little suction cup on the end of the arrow and you've remembered to moisten a suction cup not dry but moist and it will actually stick to the refrigerator door and the reason that it's sticking there is the surface tension of the water is actually creating a hydrogen bond it's the way we're able when we're taking a shower to have our shower curtain actually to a certain degree gripped the wall near the shower and so keep its position so in that sense it's very helpful it's very unhelpful if you're born too young and you have lungs that don't have how shall I say this secretion that actually is making things a little bit slippery and if there's only the water there in the lungs the lungs actually pull pull itself together and it's very difficult to take a breath in the absence of surfactant surfactant is the molecule that allows the lungs to how shall I say become more compliant for a newborn child when they're trying to breathe okay so you can imagine if we were to add detergent to this water right here the surface of the water would actually relax into bubbles okay because the basically adding a detergent or a soap to a solution of water molecules will basically cover the partial positives and negatives with the amphoteric molecule and it literally makes water wetter it will actually relax into bubbles if you take a look at the water the detergent in your dish pan the water has become a series of bubbles now instead of a flat surface and so the hydrogen bonding is gone and that's what surfactant does in the lungs okay so as we press on here I'm not going to be pushing too deeply into the ideas of chemistry you'll need to take chemistry course for the purpose of that but this is just a quick review of the molecular basis of life and some of the things that we will have to study acids and bases are definitely part of the program and it's going to be based to a degree and when water breaks down ultimately or when there is hydrogen and a large supply anything that donates a hydrogen ion like this would be considered an acid or anything that donates a hydroxide ion to a situation would be considered a base so sodium hydroxide is a base and hydrochloric acid is an acid because they're making contributions of a specific nature in this regard and we're measuring the amount of in essence hydrogen I am in any given situation so if it's neutral as is being depicted here water is neutral and that's because on average there's only one molecule of water for every 10 to the seventh molecules of water there's only one molecule of water that will high Anais into a hydrogen ion and an hydroxide ion so that's an expression that's telling us that water is a very stable molecule and liquid when it's in liquid form and so things that are of the neutral persuasion are in this range here such as milk blood blood has a pH of 7.4 you'll need to know that it's actually a range of 735 to 745 but it averages out to 74 and so many things in life whether it's milk this would be cow's milk rather than a human mother's milk but in either case we're going to be feeding our our children that our infants newborns milk because we're a mammalian species and it's going to be neutral and then things become a little bit more at this in this range over here we're becoming more acidic and basically the pH changes when we get down here into this range we're getting into the acidity of the human stomach in gastric juices and that comes that actually is in excess of what we would experience with lemon juice and then up in the other direction we have things that are household bleach or soapy types of products okay so ultimately the human body and most of this presentations outside of shall we say the stomach and the small intestine the stomach has a pH of of two and the small intestine has a pH of 8 or 8.4 somewhere through there so the rest of the body he should be maintaining somewhere in the vicinity of a neutral to a blood-related type of pH okay there's going to be buffers that we'll be considering but we'll press on here to consider just actually the molecules themselves that are commonly found in life and so in this case we're going to be looking at carbohydrates and we'll be taking a look at individual sugars for instance glucose and fructose individual sugars galactose is one of the sugars that are put together when put together with glucose forms milk sugar this is the common table sugar which is a disaccharide as you can see here which is sucrose okay so glucose and glucose is maltose and this is a much more neutral energetic type of sugar molecule and it's what's broken down from carbohydrate ultimately when we have more than two of these together we call it a Malto dextran okay galactose is is the milk sugar okay and so we'll carry on from there in our next episode