hello everybody my name is Iman welcome back to my YouTube channel today we're going to discuss structure and function of large biomolecules in this chapter we're going to cover the following points first macromolecules are polymers polymers that are built from monomers then we're going to move into carbohydrates and we're going to see that carbohydrates serve as fuel and building material then we'll discuss lipids and how they are a diverse group of hydrophobic molecules then move into proteins and how proteins include a diversity of structure resulting in a wide range of function and last but not least we're going to talk about nucleic acids and how they store transmit and help Express hereditary information now this is going to be an introduction to the four classes here um the four main classes carbohydrates lipids proteins and nucleic acids and then we're going to spend many chapters talking about each one individually in great detail so today it's more of an introduction now it might surprise you that the most important large molecules that are found in all living things whether it's from small organisms like a bacteria to large organisms like humans they can ultimately be sorted into four main classes so all these large molecules that are found in living things can be sorted into just four main things and they're known as carbohydrates they're known as proteins they're known as lipids they're known as nucleic acids all right all the molecular scale members of three out of these four classes which are going to be our carbohydrates proteins and nucleic acids are huge and therefore called macromolecules the architecture of a large biological molecule really plays an essential role in its function so like water and simple organic molecules large biological molecules are going to exhibit a unique emergent property that arises from their orderly arrangement of their atoms so then in this chapter we're going to consider how macromolecules are built and then we're going to examine the structure and function of all four classes of biological molecules we're going to discuss lipids all right and here we're going to discuss steroids phospholipids and fats all right then we're going to talk about nucleic acids we'll cover DNA and RNA we're also going to discuss carbohydrates we'll discuss mono dye and polysaccharides and in proteins we're going to take a while discussing amino acids and then um building up from primary to secondary to tertiary to quaternary protein structures now this chart here you see all four categories and their Associated terms this is going to be beneficial to review at the end after we cover each category for you to come back and look at this diagram so that you can connect all the topics that we discussed throughout this chapter for now it's really just going to serve to foreshadow the main topics we're going to cover in each of these four categories fantastic so let's get started our first topic for this chapter is the following the first thing we want to talk about before diving into the four main classes that make up all living things is how macromolecules are polymers built from monomers so the macromolecules in three out of the four classes of life's organic compounds carbohydrates proteins and nucleic acids are gonna be chain-like molecules called polymers lipids are an exception to this um but nucleic acids proteins and carbohydrates are all large biomolecules and specifically their chain-like molecules called polymers a polymer is a large or long sorry it's a long molecule consisting of many similar or identical building blocks that are going to be linked together by covalent bonds very much like how a train consists of many chain cars that are connected together all right the repeating unit that serves as that fundamental building block of a polymer polymer are these smaller molecules called monomers some monomers also have other functions of their own all right so let's break this down the term monomer originates from mono which is one in mer which is part there are small they are small molecules that can be joined together to form more complex molecules called polymers all right now although each class of polymer all right although each class of polymer is different is made out of different types of monomers the chemical mechanism by which cells make and break polymers are basically the same in all cases so when we discuss carbohydrates all right we're going to talk about what the monomer for carbohydrates is and how they connect to form a polymer of carbohydrates and what that name for that polymer of carbohydrates is called then when we move into proteins we're going to discuss the monomer unit of proteins what you'll notice is it's not the same same monomer unit as it was for carbohydrates that's what's going to help us identify carbohydrates from proteins all right then we're going to take that monomer unit in proteins and we're going to see how we can connect those monomers to build a protein polymer and what a protein polymer is called then when we move to nucleic acids we're going to discuss what the monomer unit for a nucleic acid is what you'll notice is it's very much different from the carbohydrate monomer unit and very much different from the protein monomer unit and again that uniqueness in monomer units for each of these macromolecule main classes is what's going to help us distinguish between each all right but what is the same what is the same is the chemical mechanism that we're going to learn on how to connect monomers to build up polymers whether it's carbohydrates nucleic acids or proteins all right so let's discuss that a little bit well monomers are connected are connected by a reaction in which two molecules are covalently bonded to each other and how this happens is with the loss of a water molecule and so what we can say is monomers are connected by a dehydration process if we look here all right if we look here Pretend This is a monomer right here and this is another monomer right here I'm sorry all right forget this part we can connect these two monomers by a dehydration process what that means is the hydrogen in this monomer unit and the hydroxide hydroxide group in this other monomer this alcohol group if you will all right what they're going to do is they're going to form water and leave and that's going to form a covalent bond between these two monomers three and four all right we're ignoring one and two pretend those are not there all right so how we connected these two monomers is the hydrogen of one monomer and the alcohol group O H group of another monomer left together to form a water molecule and resulted in a covalent linkage between these two monomers so monomers are connected by a dehydration process and it's a dehydrator nutrition process because the two molecules that leave off of monomer 1 and 2 form water all right and so we're dehydrating these monomers to form a covalent bond between the two all right so this is known as a dehydration reaction again when a bond forms between two monomers each monomer can contributes part of a water molecule that is then released during the reaction so one monomer is going to provide a oh group or a hydroxyl group while the other is going to provide a hydrogen and this reaction is usually repeated as monomers are added to the chain one by one making a polymer so we added these two together then we can add another monomer to this chain and another monomer by the same dehydration reaction so that's how you built monomers all right what if you already have a polymer all right so a polymer is a all right is is the addition of many molomers monomers together all right you have a polymer now polymers can be disassembled to monomers all right and the way that this is done is by hydrolysis this is a process that is essentially the reverse of a dehydration reaction hydrolysis means water breakage the bond between that's right let's erase this the bond between monomers all right is is is broken or can be broken by the addition of water so to this covalent bond if we add water all right the bond between these monomers is broken by this addition of a water molecule where a hydrogen from the water attaches to one monomer and a hydroxyl group attaches to the other and so this water is added to this polymer all right between this this bond between monomer three and four one monomer gets a hydrogen the other gets a hydroxyl group and so we cause a breakage between these monomers all right and as a consequence right one monomer gets a hydrogen the other monomer gets a hydroxyl group and that chain there is broken all right so what we can summarize here is monomers are connected by a dehydration process so if water leaves all right through the donation of a hydrogen and a hydroxyl group from two monomers then they can form a bond together all right or if you have a polymer you can disassemble the polymer to to monomers by hydrolysis by adding water now what we can ask next then is well what is the basis for diversity in life's polymers right these molecules they're constructed usually from 30 to 50 common monomers and some others that occur rarely building a huge variety of polymers from such a limited number of monomers is kind of analogous to the fact that we can construct hundreds of thousands of words from only 26 letters of the alphabet so the key to diversity is Arrangement all right so even though we have a limited number of monomers in our category of carbohydrates and and nucleic acids and proteins we can still build up to a diversity in these polymers because the key to diversity is Arrangement the particular linear sequence that the units follow however the analogy kind of falls short of describing the great diversity of of macromolecules sometimes because most biological polymers have many more monomers than the number of letters in a word even the longest ones for example proteins are built from 20 key amino acids that are arranged in chains that are typically hundreds of amino acids along the molecular logic of life is really simple but elegant and it is this small molecules common to all organisms are ordered into unique macromolecules and those macromolecules provide the diversity in in our lives in the in in life itself all right and that's going to help us transition into talking about our first class of of large biomolecules so despite the immense diversity molecular structure and function can be grouped roughly by class and we said that our four classes are proteins nucleic acids lipids and carbohydrates the first class we're going to talk about today is carbohydrates carbohydrates serve as fuel and building material let's get into it now the building block for carbohydrates are something known as monosaccharides all right and we're going to discuss what monosaccharides is but carbohydrates are essentially what you can think of as sugars they include sugars and Polymers of sugars the simplest carbohydrates are called monosaccharides or simple sugars these are monomers from which more complex carbohydrates can be built disaccharides on the other hand disaccharides are double sugars consisting of two monosaccharides that are joined by a covalent bond so disaccharides are just two monosaccharides added together so monosaccharide is our basic building block our monomer in carbohydrates two of these monosaccharides two of these monomers form a disaccharide all right and then carbohydrate macromolecules can also be polymers so you can have a collection of monosaccharides that are added together in many different ways and those polymers are called polysaccharides so this is when you have many monosaccharides added together in different ways as well all right so those are called polysaccharides they're composed of many sugar building blocks now let's really focus on this building block of carbohydrates these monosaccharides monosaccharides generally have molecular formulas that are some multiple of the unit ch2o all right some multiple of this basic unit now glucose the most common monosaccharide has the molecular formula C6 h12o6 you're going to get really familiar with this molecular form formula for glucose notice notice how it is some multiple of the unit ch 2o all right it is some unit it's this unit multiplied by six c one times six is C6 H2 times 6 is 12 so h12 and o1 times 6 is 6.06 C6H12O6 is some multiple unit of ch2o all right and monosaccharides generally have molecular formulas that are some multiple of this unit all right so glucose has this molecular formula and it is a common monosaccharide it is the central importance of it's It's of central importance in the chemistry of life now in the structure of glucose we see the trademarks of sugar this molecule has a carbonyl group all right it has a carbonyl group right here there's going to be a carbonyl group and multiple hydroxyl groups all right and this is a carbonyl group because they haven't drawn it out for us but it's pretty much um the carbonyl group here all right and that means by the way if you remember our carbonyl group is carbon double bonded to oxygen all right and multiple hydroxyl groups do you remember what our hydroxyl groups those are o h groups all right now depending on the location of the carbonyl all right depending on the location of the carbonyl and multiple hydroxyl groups all right we can determine different kinds of sugars all right so depending first on the location of the carbonyl as sugar is either an aldose or aldehyde sugar or a ketose or Ketone sugar all right so those are kind of two categories that you can have of sugars glucose for example is an aldose um sugar fructose for is an isomer of glucose and it is a ketose sugar now we're going to get into those terms much much later but as a quick hit most names for sugars what you'll notice they end in OS o-c-e all right so that's going to help you identify sugars now another Criterion for classifying sugars is the size of the carbon skeleton which can range from three to seven carbons along glucose and fructose and other sugars commonly have six carbons all right typically have six carbons and they're called hexoses all right three carbon sugars are known as triosis and pentoses are five carbon sugars those are all very common carbon skeleton based sugars now monosaccharides particularly glucose are major nutrients for cells and in the process known as cellular respirations cells extract energy from glucose molecules by breaking them down in a series of reactions not only are simple sugar molecules a major fuel for cellular work but but also their carbon skeletons also serve as raw materials for the synthesis of other types of small organic molecules like amino acids and fatty acids now an important thing to understand is how we can add monosaccharides to build disaccharides and polymers all right so a disaccharide like we said usually consists of two monosaccharides that are joined by this linkage right here this is called a glycosidic linkage it's a covalent bond between two monosaccharides that's formed by a dehydration reaction all right so this dehydration reaction is going to take it's gonna take a hydrogen from one monosaccharide and a hydroxyl group of another saccharide and these are going to leave as water all right you have this alcohol this this oxygen I'm sorry that's left over all right and so you form this covalent bond between the two monosaccharides and they're attached by this oxygen all right so this dehydration reaction results in a glycosidic linkage between two monosaccharides all right and when it's two monosaccharides you call this a disaccharide of course you can build it up and you can form more glycosidic bondages between more monosaccharides and grow this branch and what you get here then are polysaccharides polysaccharides are macromolecules polymers with a few hundreds to a few thousands monosaccharides joined by glycosidic linkages now some polysaccharides serve as storage material and they're hydrolyzed as needed to provide sugars for cells other polysaccharides can even serve as building materials for structures that protect the cell or the whole organism and the architecture and function of a polysaccharide are really determined by its sugar monomers and the position of those glycosidic linkages now both plants and animals really store Sugar for later use in the form of a storage polysaccharide so the uses of polysaccharides in in many organisms is very important to the survival of that organism all right so we've covered carbohydrates now I'm going to stop here and next time we're going to start by discussing lipids let me know if you have any questions or comments down below other than that good luck happy studying and have a beautiful beautiful day