hi guys in this video we'll be looking at the biochemical basis of life biological molecules monomers and polymers condensation and hydrolysis reactions and then we'll finish with a summary so we don't need to look far to realize that in the natural world there is such a huge variety of life even just looking at the animal kingdom alone we can see things like insects fish mammals dogs reptiles all sorts of different animals pop into our heads and then of course we've got other kingdoms like we've got the plant kingdom we've got fungi like mushrooms and we've got things like bacteria as well and when you consider all of the life there's so much variety in their size shape color functions reactions etc that you think that they're all built up of lots of complex differences but despite all of this enormous diversity in the life on earth every organism depends on the same biochemical basis of life and we call this carbon chemistry so even though there is such a massive diversity in all the organisms they all boil down to the same kind of molecules and we call the study of these molecules that give rise to life biochemistry and therefore there's a similar biochemical basis of life and all centers around an element known as carbon which has particular properties allowing life to exist the common ancestor that gave rise to all of us uses this carbon chemistry and because all life is descended from this despite all of our diversity we all base ourselves around carbon so down here we would have seen the last common ancestor which is currently unknown as it evolved into various species of course through time different branches branched off into different types of organisms and different kingdoms as well for example on one extreme we have the archaea which are specific type of organisms which can withstand very tough environments we've got animals and plants commonly called eukaryotes and we have bacteria too and while there are significant differences between all of these they all rely on carbon chemistry so what makes living things different from non-living things are particular types of molecule based around carbon and the important properties that it has as an element so carbon as an atom exists with the ability to form four bonds so carbon as an atom has the ability to make a bond with four other structures or four other atoms they can be different groups or the same group but the ability of this means that the carbon atoms can bond into lots of different things and bond together to form more complex molecules and you can imagine that if they keep forming different bonds each of them being allowed to bond to four things then the ability to make a complex molecule which could be very large is very high so we can make lots of different sizes of molecules based on carbon and it can join to lots of different chemical groups and actually what we find is that carbon as a skeleton like this acts as a backbone for organic or carbon containing molecules and these are found in all living organisms so the carbon chemistry is based on the fact that carbon combine to lots of different things and when it does it acts as the backbone for the organic groups inorganic always refers to carbon containing so when you think of inorganic we're thinking of ions or things like zinc copper water things which don't have carbon in them when we think of organic we're thinking of things like sugars and proteins which we'll talk about next so the biological molecules which make up life are based on carbon as we just said and there are four main types of biological molecule found in all organisms regardless of where they belong in that family tree and those four types are carbohydrates sometimes referred to as sugars lipids sometimes referred to as fats we have proteins and we have nucleic acids like dna so these are the four groups and within these groups there are lots of different types for example there are many types of proteins which build up the body there are many types of sugars that we can find in our food and in the body too and all of them are based on carbon but some of them have key features where they contain a small number of other chemical elements so let's take each one in turn carbohydrates you can work out what they contain from their name they contain carbon hydrogen and oxygen and if you look at the name we've got carbo for carbon hydra for hydrogen and eights usually refer to oxygen for example when you see something like sulfate it's sulfur bounded to oxygen so when you look at this this is an example of a carbohydrate and let's look for these various elements we can see carbon various times hydrogen in lots of different places and it contains oxygen too lipids contain the same elements as carbohydrates so that's carbon hydrogen and oxygen but it just is arranged in a different way so we can still see that we have carbons usually in a long chain with hydrogen atoms and oxygens normally at the end so they're the same elements as carbohydrates but a very different structure overall proteins can have more than this they have carbon hydrogen and oxygen but they also contain nitrogen in an amino group and they also can contain sulfur for some particular types of amino acid so here's an example of an amino acid and we'll talk about what amino acids are in just a moment as part of a protein and we can see that we've got this carbon element again with hydrogens and oxygens but we also have a nitrogen and we have sometimes this sulfur group which isn't always present but when it is it's usually in a very low number and then finally looking at nucleic acids which is that fourth group they contain carbon hydrogen and oxygen as before they contain nitrogen like protein does and it also contains phosphorus which is another non-metal element so looking at this it's quite a complicated molecule but we can see carbon again forming that nice backbone through the structure we've got hydrogens and we've got oxygens we've got a few nitrogens this time usually bound in some sort of ring structure and we've also got a phosphorus atom usually just the one in a nucleotide so as you can see all of these biological molecules have the same feature in common there's a carbon skeleton forming the kind of backbone or foundation of the molecule and they usually have hydrogen and oxygen around them too but then other elements sort of wedged in there they often contain lots of atoms compared to something like a water molecule which just has h2o three atoms but these tend to have many tens of atoms sometimes more so we often call them not just molecules but macromolecules with the macro meaning large molecule meaning a group of atoms bound together so in order to understand how biological molecules assemble themselves we have to understand the concepts and difference between monomers and polymers so a lot of biological macromolecules don't just exist on their own but they exist as what we call polymers and a polymer is something which is built up from lots and lots of repeating smaller building blocks and those building blocks individually are called monomers so let's show an example of this monomers are individual molecules making up a polymer you can see by the name we've got mono meaning one so that's one single unit polymer meaning many so lots of these one units joined together to make a many unit so just to illustrate that using a kind of lego brick idea here we've got three monomers monomer number one monomer number two number three and if you add them all together you get this chain and you stick them together into one single polymer and this is how most biological molecules exist and it's this concept of building up larger larger chains of molecules which help us understand how plants can get so tall how are their stems so long how are our bones so long they're not made of individual units they're made of lots and lots of units joined up into massive structures that allow us to be as big as we are so by definition a polymer is a long chain composed of many individual monomers which have been bonded together in a repeating pattern and the point is it is a repeating pattern because usually there's some sort of structure of the units following a sequence or it can be the same unit one after another in a massive chain so for example in carbohydrates the monomers are known as monosaccharides and the polymers are known as polysaccharides so the saccharide part refers to sugar and we either have one on its own as mono which is the individual unit and then when they're joined together in a chain we have a polymer and this would be a polysaccharide so you'll notice that with biological molecules the mono and the poly bit stays the same the actual name of the bit after that is what defines it into which group so saccharide is referring to carbohydrates when we're talking about proteins it's slightly different the monomers we call them amino acids and then the polymers when lots of these amino acids join together are called polypeptides so it's not as simple as carbohydrates this time but we have one unit as being an amino acid and there are lots of types of amino acids and remember these contain the elements of carbon hydrogen oxygen nitrogen and sometimes sulfur and then as we join these up into long chains we form one long polypeptide you can kind of think of it as a peptide as an amino acid so poly meaning lots of them in nucleic acids we have the monomers known as nucleotides and polymers are polynucleotides sometimes you will see it as mononucleotides as well so here's a string of nucleotides as a polynucleotide and one of these single units would be a nucleotide so hopefully you can see the similarities between these groups as we go through the only one that's slightly different are the lipids they're still macromolecules built on carbon as we said before but they're not really classed as polymers they don't have smaller repeating monomers they may have an extensive length like the rest of the molecules and they may extend much further than proteins carbohydrates and nucleic acids but they're not made up of units that repeat themselves they're simply a very long chain so actually what they're made of instead are a number of different base units joined together in a non-repeating pattern so the general structure that we tend to see is a molecule known as glycerol and then when glycerol is bound to these units these tend to be identical to each other and these are known as fatty acids and all together the structure of glycerol bound to three fatty acid makes a triglyceride so now that we've gone through what the difference is between monomers and polymers we have to understand how they're formed it's really important because during the survival and the lifetime of an organism things need to get broken down and some things need to be built up for example when we digest our food we need to break down polymers into smaller units so that we can send them around the body and use them if we're building our bones if we're growing through childhood or a plant needs to reach the sun we need to build up larger molecules from smaller molecules so we need ways and we need to understand how we go from one to the other and back again so we've said that polymers are formed from monomers and this is done by what we call a condensation reaction so there'll be two types of reaction we need to talk about one where we build and one where we destroy so when monomers come together and they form a polymer we call this condensation and a condensation reaction has particular features in a condensation reaction there is a bonding of one monomer to another whether that other monomer is on its own or it's the end of a chain doesn't matter so a monomer is bonding on to either an existing chain or another monomer and when this happens not only does the bond form but a molecule of water is formed in the process too so let's have a look at this we've got monomer one and monomer two and they're coming together and in the coming together they make a polymer and in this case we've got two so we're going to call it a dimer now we can have monomer dimer meaning two we can have trimer meaning three and eventually it becomes so many that we just call it a polymer but there are prefixes you can put before whereas die means two so now we have a dimer we have a bond formed and also in the process we formed a molecule of h2o or water which then leaves the monomers how does the water get formed well you need to look at the groups in the monomer whatever monomer we're talking about whether this be an amino acid or a monosaccharide or whatever there's always going to be the coming together of two groups there's going to be the oh of one monomer and an h of another monomer and this is where the water comes it's called a hydroxyl group which is an oh from one monomer and a hydrogen just on its own is an h from another monomer so as these two come together they form their bond but in doing that bond formation they have to lose these groups because they're in the way so these snip off and form a water molecule so you get your dimer which is formed and h2o so it's the oh of one monomer and the h of another and you'll find that any monosaccharide or amino acid or individual nucleotides will always have oh and h groups and looking back on those carbon skeletons of those molecules you can spot these quite easily so by definition a condensation reaction is a reaction that occurs when two molecules combine to form a more complex molecule with the removal of water and that can be a monomer joining a chain or just two monomers binding together so that's how we make polymers what about breaking them down for example if we're digesting foods polymers are broken down into individual monomers by hydrolysis reactions this is going backwards now this is the reverse of condensation so here we have a polymer breaking down into individual monomers and this is known as hydrolysis hydrolysis breaking it down condensation would be forming it and in this respect we can talk about it as the reverse of condensation hydrolysis reactions require water so we have to put water in in order to break the bond between the monomers so here we have a dimer formed of two monomers and a bond in order to break that bond a water molecule is added and it goes into the bond and pulls the monomers apart because what the water is now doing is replacing these two groups where one monomer has that hydroxyl group and the other monomer is given a hydrogen and you can see that water can provide these because we've got two h's and an o and then when these groups form the bonds can no longer form because they're sort of in the way the chemistry is different so now the monomers separate and we're left with two monomers so you can see how it's the direct reverse of condensation where in the condensation reaction we removed water to make that bond so by definition a hydrolysis reaction is a reaction occurring when larger molecules are broken down into smaller molecules with the addition of water so the condensation and hydrolysis reactions are used to build up or break down all of the biological molecules lipids nucleic acids proteins and carbohydrates and here's a table just to summarize them in condensation monomers are joined together whereas in hydrolysis monomers are broken apart condensation forms water and hydrolysis requires water if you have trouble remembering which is which remember that condensation is what you see on the sort of mirror in the bathroom or on a cold bottle where water starts forming in droplets so it's forming water and hydrolysis one lysis means to break so in this case we're adding water and we're breaking it into two to make those groups again and in condensation we form a bond whereas hydrolysis we're breaking again breaking break lysis and condensation and hydrolysis reactions are very important reactions taking place in all the cells of organisms so they're examples of metabolic reactions making useful products hey guys i hope you enjoyed the video if you're looking for an amazing a level biology resource join me today in my series of engaging bite size video tutorials just click the snap revise smiley face and together let's make a level biology a walk in the park