hi it's Mr Anderson and welcome to biology Essentials video number 14 this is on environmental matter Exchange in other words how life exchanges matter with its environment uh the picture I started with is a picture of Biosphere 2 um before I talk about Biosphere 2 I should probably talk about biosphere 1 biosphere 1 is our planet and wherever life is found on our planet but in the late ' 80s early '90s some people built Biosphere 2 it's massive and the idea was that you would lock people inside here and they would stay inside there for 2 years now they would constantly get energy in the form of sunlight but all the matter inside there would have to be recycled for 2 years now that seems crazy but that's our planet in other words the matter on our planet has been recycled over and over and over again we constantly get an influx of energy but the matter that we have today is the matter that we've always had on our planet and so how we exchange that matter is super important so to summarize we going to talk about is how we utilize uh matter how we get matter from our environment um the big four types of matter I'm going to talk about our our water uh carbon diox or excuse me carbon nitrogen and phosphorus um and how we acquire those things now in order to acquire it I'll talk a little bit about surface area to volume and the ratio of that and two examples of those in living things and how we want to maximize our surface area to volume ratio I'll talk of the importance of water and how it acts as a universal quote unquote solvent um and I'll also talk about why carbon nitrogen and phosphorus are important in the four major macromolecules that we have in other words carbon is found in all four of these it's ubiquitous in our macro molecules nitrogen is important it's found in uh proteins and it's also found in nucleic acids and then finally phosphorus is important phosphorus it it is found in lipids and also has a huge role in nucleic acids and so that seems kind of confusing but I'll try to pair that down uh a little bit hopefully first of all I want to talk about a little bit of math the ratio of surface area um to volume in other words the ratio of a surface area of an object to its volume and so to make it simple I started with a simple threedimensional figure called a cube and so let's first do the math on a cube that has a side of two units and then I'll show you surface area to volume of a side where it has side area one and so let's first of all start with the surface area so the surface area is going to be all the sides that are on the outside so you can think of it like a dice uh and so to do that I'm going to have to take the surface area of one side so the surface area of this would then be two uh time 2 and so the surface area of this side would be four but the surface area that is four and that is four and this over here is four and so it' be 6 * 4 and so it's going to be 24 and now let me do the volume well since this is two and that's two the volume is going to be um 2 * 2 * the depth is 2 so it's going to be eight and so the surface area to volume ratio of a cube that is uh a a side length of of two is going to be three um if I were to do the same thing over again with a side area of one well the side area one that means each side would be one so this total would be a surface area of six the volume would be 1 * 1 * 1 or it' be 1 and so it'd be six and so what happened to our surface area to volume ratio as we made our Cube smaller it got bigger and I could keep doing math for a long time and if you were to do this over and over again you'd find that the surface area to volume ratio is going to get bigger and bigger and bigger and bigger over time and so why are cells small why do we find folding why do we find root hairs all of these things because if we can maximize the surface area to volume ratio we make things smaller and we can get more of this Mass are inside and so these are the root hairs in other words a root are going to have these tiny hairs and what that does is maximizes the surface area so it can take in more matter because a plant needs to get these um essential nutrients inside and also there are fungus growing on here which actually increases the surface area even more and it also tells us why cells are small so it also tells us why um red blood cells even have a little curve on the inside to maximize that surface area volume and and so no matter how big you are if you're an elephant the cells of you are going to be the same as the cells of a mouse and the reason why is we're maximizing that surface area to volume that's a little too much math and so life requires four major macro molecules and those four major macro molecules are carbohydrates we use that for energy proteins that's pretty much what we're made up of when you're looking at me you're just looking at uh proteins lipids uh lipids are super important they make up the uh cell membranes that surround all living things and then finally nucleic acids that's going to be the RNA the DNA it passes hereditary material from generation to generation and so um all of these things require matter and so water I'll start with that first water is a polar molecule what that means it has if if this is oxygen and these are the hydrogens it's going to have a negative charge here and a positive charge up here as a result of that since water's polar it's really good at absorbing water it's really good at surrounding hydrophilic protein surrounding cell membranes at least on the outside and since uh nucleic acids have a charge they're really well uh they do a good job of dissolving those as well and so why is life require water requires water so it can act as a solvent to surround living material because if it wasn't then we wouldn't have all these chemical reactions we really wouldn't had life and where weever find life on our planet we also find water and vice versa and so water is required for all of these things what about carbon well carbon you can see it right here carbon makes up the skeletons of of sugar makes up the proteins makes up the skeletons of of nucleic acid and also makes up lipids um so this whole hydrocarbon tail and the head is going to be made up of carbon as well let's go nitrogen nitrogen where's nitrogen found well nitrogen's found in amino acids and amino acids are the building blocks of protein so nitrogen is going to be found inside proteins and then nitrogen also is going to be found on the inside of uh DNA and and the nitrogen bases require nitrogen as well and so to make all of these things we require these essential uh chemicals and then finally phosphorus well where's phosphorus found phosphorus is going to be found in the heads of these phospholipids uh that make up the membrane and then phosphates are also going to be found to on the side chains of the of DNA or it's going to be found in the backbone of DNA and RNA and so if we don't have carbon nitrogen phosphorus if we don't have water then we don't have life and so we require this matter from our environment now the interesting thing though is that it's recycled in other words the sugar that I had in my breakfast cereal this morning that carbon doesn't just go away that carbon inside me will be eventually as I get broken down will be used by other living things will become carbon dioxide and so that'll be recycled over time in other words we're set with a given amount of each of these uh atoms and so we have uh four Cycles we have the water cycle um and that just is going to move water around how do I get water inside me I'm going to do that just by drinking water we've got the carbon cycle carbon cycle most of that actually sits as carbon dioxide in the atmosphere we take it in through photosynthesis and we get rid of it through respiration nitrogen we're getting through bacteria uh in the soil actually we're um fixing nitrogen in the atmosphere and making it usable and then as we die we return that nitrogen then phosphorus is actually going to sit here in the rocks and then we get that plants will get that through the soil and then we get that by eating plants and so we require these four things these this matter um it's set on our planet we live in this biosphere um that is planet Earth and so we constantly use those um those nutrients over and over over again we use those atoms over and over again but luckily we have an influx of energy from the Sun and so the next time you're thinking you're drinking a little bit of water you should think to yourself the atoms inside that water were once inside water that Einstein drank or water that a dinosaur drank or water in a primordial sea um and so matters constantly exchanged between living things uh and uh through time and so I hope that's helpful