hi everyone this is kim and we are starting to talk about the macromolecules starting with carbohydrates so just a reminder that the monomers of carbohydrates are called the monosaccharides the polymers are called the polysaccharide so monosaccharide means one sugar and polysaccharides means many sugars we're also going to see something called disaccharides so if you look at the different categories of carbohydrates the disaccharides are two sugars bonded together and we'll be looking at three different disaccharides that are biologically significant that you should know about and then here's the list of monosaccharides and polysaccharides we'll talk about and we'll be looking at the structures of each of these and talking a little bit about the characteristics of them for the polysaccharides we're going to talk about the storage polysaccharides that really are the storage form of energy for those organisms and then structural polysaccharides actually form structures so we'll be looking at cellulose and chitin that's pronounced chitin not chitin so let's first look at monosaccharides the first thing i want to tell you about monosaccharides obviously monosaccharides are the monomers of carbohydrates so monosaccharide means one sugar and all monosaccharides with one exception have the same general chemical formula and that is they have carbon hydrogen and oxygen but they have equal numbers of carbon and oxygen molecules and twice as many hydrogens so they're all ch2o times some number so if we had three carbons in the sugar that would mean we'd have six hydrogens three oxygens so equal number of carbons and oxygens twice as many hydrogens here's another one c5 h10 o5 so again equal number of carbon and oxygen twice as many hydrogens and then finally we have three significant sugars that are c6h12o6 so all three following that same general formula here is a picture of sugars that are those three chemical formulas that i just showed you so these are sugars carbohydrates drawn in the linear form it's important to remember one of the characteristics of carbon chains so this is a chain of carbons one of the characteristics of carbon chains is they form rings in solution and especially sugars form rings in solution so in your body these sugars would actually be in their ring structure i i will usually show them in their linear structure so you can identify these as being sugars as being carbohydrates and i'm going to show you the clues for telling these are carbohydrates using the functional groups that you learned in the intro to organic chemistry videos so let's look at the first clue that you're looking at a carbohydrate this is the first clue and you can see that in all of these sugars carbon double bonded to an oxygen that had a specific name when we looked at the functional group do you remember what that carbon double bonded to an oxygen is called it's called a carbonyl group so if you see a carbonyl group that is your first clue that you are looking at a sugar so carbon chain with a carbonyl group and you can see that carbonyl group doesn't have to be at the end of the molecule here in fructose you can see it's on the second carbon in the chain the other clue that you are looking at a sugar is we have multiples of this functional group do you remember what that one's called multiple hydroxyl groups so these two things combined tell us we are looking at a carbohydrate and you can see these all follow that same general formula equal numbers of carbons and oxygens and twice as many hydrogens there's actually one sugar missing in this picture at the bottom there are three sugars that have the same chemical formula c6h12o6 so the one that's missing is galactose and those are all three what we call structural isomers remember structural isomers if it's an isomer it means it has the exact same chemical formula but different arrangement of those same atoms so different structure and you can see the three different structures here so they're all c6h12o6 but different arrangement of those same atoms you need to know when you see the names glucose galactose and fructose that those are all three monosaccharides these are the simplest form of the sugars your body has to break all sugars down to monosaccharides to get them into your cells so disaccharides and polysaccharides cannot enter your cell you have to get it down to the monosaccharide form to be able to get it into your cell and use it as an energy source the other two monosaccharides you need to be familiar with and you will see them again when we talk about nucleic acids ribose and deoxyribose these are five carbon sugars so when they form a ring that ring has five points and it's called a pentose sugar meaning it's a five carbon sugar and it forms a pentagon when it forms its ring structure ribose is the sugar that is part of the rna type of nucleic acid and we'll look at that in more detail when we look at nucleic acids so this is a sugar on its own but it can be part of another molecule and you'll see that there are other parts attached to this sugar when it makes up a nucleic acid deoxyribose is the sugar that is part of dna and deoxy without d is without day and this is referring to oxygen and if you look at the difference in structure between ribose which has an oh here and deoxyribose just has the h here so that oxygen is missing in the deoxyribose otherwise exact same structure for those two sugars so dna is going to use the deoxyribose sugar should have written those backwards deoxyribose is going to be part of the dna molecule and ribose is going to be part of the rna molecule sugars are the most important foods you eat and i know the current trend is low sugar low sugar low sugar low carb low carb low carb and we will talk about that a little bit today but here's the reason you need a constant supply of sugar in your bloodstream cellular respiration what is the first reactant in that equation this by the way is the general equation for cellular respiration i know i've written this formula a few times now you will learn about cellular respiration in great detail when we get to that unit on energy for now you should just know the general equation and realize that we combust glucose break the bonds of glucose and use that energy to make atp atp is the energy currency of the cell if you don't have a constant supply of glucose you are not going to be able to make enough atp to power reactions in your cells if cellular respiration completely stops you die there are poisons that block critical stages of cell respiration and will kill that organism so lots of pesticides or rat poisons so pesticides that kill insects that kill plants that kill even certain other pests block key steps in cell respiration and kill that organism you have to have a constant supply of glucose in order to make atp to drive the chemical reactions in your cells that require energy it is the most important thing you eat if you do not eat enough glucose you are going to do other things to make energy and over time that can become damaging to your body so being on a low carb diet short term is okay long term you are going to cause damage to your body it's not good now this is not a new nutrition class so we won't talk a lot about it but just know that if you don't have glucose available one of the things that happens is you go into what's called ketosis in which ketones become elevated in your blood and urine due to breaking down fatty acids into sugars so that you can fuel cell respiration there's only so much of that your body can do on a regular basis before it becomes damaging you can also do something called gluconeogenesis and let's break down this term genesis means create neo is new and this is of course referring to glucose we create new glucose from using proteins in the body breaking down proteins as an energy source you don't store proteins in your body you don't have a storage form of proteins you do have a storage form of fatty acids from the fats you eat and also from carbs that don't get used long-term storage of those is fat and we'll talk about that a little bit today so gluconeogenesis is taking protein usually from your muscles and your organs and using that to make glucose that obviously can become damaging so using fatty acids and proteins as your primary source of energy is okay short term but long term it can become very damaging you need to eat healthy carbohydrates as part of your diet you can't eat too many carbs because you will send them to long-term storage if you don't burn them and long-term storage in the body is fat fat is more energy dense and that's our long-term energy storage in the body is fat but short-term you are going to store what's called glycogen in your liver and you're going to slowly release that glucose into the bloodstream because you need a constant supply and we will talk about that in a little more detail these are just bigger images than those sugars so again carbonyl group and multiple hydroxyl groups that's how you will identify this as a carbohydrate and you will need to be able to do that on the exam when two monosaccharides combine they form a disaccharide and we'll look at that in a minute but first i just want to quickly show you again the ring structure i showed you the ring structure of a five carbon sugar this is the ring structure of a six carbon sugar so this is glucose in solution and you can see this is a six carbon sugar it's called a hexose sugar forms a hexagon okay remember before we saw a pentose sugar a five carbon sugar so sugars form rings in solution we would combine two of these sugars through dehydration reaction remember dehydration reaction is how monomers are linked together to form polymers so here you can see removal of water where does that water come from you can see there's a hydrogen being removed from one water in a hydroxyl group from the other i'm sorry hydrogen being removed from one sugar hydroxyl group being removed from the other sugar to form water so two hydrogens and an oxygen h2o now those sugars are linked together this term glycosidic linkage this is the specific term used for the covalent bond between monosaccharides so it's the covalent bond that forms carbohydrates in disaccharides and polysaccharides so it's just a very specific name for that type of bond you can see there's an oxygen in the middle there that oxygen is this one right there this is a disaccharide two sugars also something i didn't point out before notice that saccharide has two c's so just be sure when you're spelling it you use two c's to spell disaccharide monosaccharide polysaccharide so this disaccharide is made of glucose plus fructose and it is called sucrose sucrose is a significant sugar to know about because this is how plants transport sugars through their tissues if you go to the store and buy a bag of sugar you are buying sucrose we harvest it from certain plants sugarcane sugar beets so sucrose is a disaccharide made of glucose plus fructose sucrose cannot get into your cells in order to get sucrose into your cells you need to break it down into the monosaccharides using an enzyme called sucrase so sucrase enzyme would break that sucrose back down into its monosaccharides it would hydrolyze the bond of that disaccharide back into the monosaccharides this is just one of the three disaccharides you should know about here's the whole list lactose you already know about from our natural selection videos remember we talked about lactase enzyme so lactase enzyme would be used to break lactose back down into glucose and galactose so it could get into your cells and if you don't make lactase enzyme as an adult that is the normal genetic condition for humans there is that gene mutation that offered a survival advantage and is now very common in certain groups of humans that allows them to still make lactase enzyme as adults and use lactose sugar as an energy source if you don't have that enzyme remember you can't get a disaccharide into your cell so lactose just remains undigested ends up in your colon and causes some issues the other disaccharide you should know about is maltose so maltose is found in wheat and it's made of just two glucose molecules bonded together lactose of course is milk sugar and sucrose is found in plants so those are the three disaccharides you should know about for each of them you should know what two monosaccharides combine to make the disaccharide so each one of them has glucose and then if you know the other three structural isomers that are c6h12o we use all three of them fructose galactose glucose more than two sugars bonded together is a polysaccharide and there are two forms of polysaccharide in living organisms that are what are called storage polysaccharides and those are an energy source two major storage polysaccharides we're going to talk about starch is how plants store glucose and glycogen is how animals store glucose there are then polysaccharides that actually form structures in organisms cellulose makes up the cell walls of plants and we'll look at that in more detail when we talk about the cell and then chitin is found in several different kinds of organisms it's found in some protists in their skeleton it's found in the cell walls of fungi and it's found in the exoskeletons of arthropods we use it also to make surgical thread dissolving stitches are made from chitin here are the two different types of starch and it's hard to see so i'll write this bigger amylose and amylopectin they're different in their structure you can see amylopectin is more complex in structure it's branched oops sorry when something's called branched it means rather than just being one line of the same thing it has a branch to it so you can see this has a side branch compared to this whereas amylose is just one curly gene of glucose so they're both chains of glucose and this is the storage form of energy in plants these are broken down by two different enzymes you actually start digesting amylose in your mouth with an enzyme called amylase so i'm going to write that up here because it's hard to see amylose remember we say it's hydrolyzed hydrolysis breaking down a polymer into monomers by it's hydrolyzed by amylase remember enzymes end in ase and they tell you what they do amylose is hydrolyzed by amylase in your saliva so this starts in your mouth you do get some amylase that comes into your small intestine also remember in the digestion story that most of your chemical digestion occurs in that first part of the small intestine and we do have some that comes into the small intestine as well amylopectin is really mostly all digested in the small intestine but the digestion of amylose starts in your mouth so when you're chewing that carb in your mouth you can almost start to taste that sugar that's why things like french bread and white rice tastes so good i mentioned already that a constant supply of glucose is incredibly important and that brings us to a very important topic in biology called homeostasis if you go on to take physiology you will learn a lot about homeostasis homeo means same and stasis means state these are processes in the body that serve to keep certain factors level the same at a set point so things like body temperature we have a lot of mechanisms that serve to keep our body temperature constant because remember proteins can't function outside a certain range of temperature and ph so we also have mechanisms that keep our ph constant another very very important one our blood glucose levels have to remain constant so we have mechanisms for keeping our blood glucose levels constant there are two opposing hormones that are important to know about that are involved in blood sugar regulation and they're both produced by the pancreas and those two hormones are called insulin which i'm sure almost all of you have heard of oops and the other one is called glucagon they're called opposing because they do two different things i mentioned before when we looked at this list of polysaccharides that there are two types of storage polysaccharide so when we're eating carbohydrate we mostly eat starch okay this is the major source of carbohydrate that we eat we obviously eat some disaccharides and sometimes we even eat monosaccharides but we also eat a lot of starch we break that starch down through digestion it's released into the bloodstream and here's the thing about releasing that into the bloodstream it's broken down into glucose so let me go back here i'm going to erase part of this so we have a room i should have another slide here but i don't okay starch is a chain of glucose so we're going to use enzymes and we're going to break down starch through hydrolysis during digestion and that can happen in the mouth or it can happen in the small intestine i'm just going to say si for that and it gets broken back down into glucose that glucose now goes into the bloodstream and it gets into your cells why do we need glucose what reaction requires glucose cell respiration we need glucose to make atp we're doing that all day every day i've read that we make and use our body weight in atp every day that's pretty crazy so we need a lot of glucose to do that here's the deal though glucose is a very big molecule it can't hang around in your bloodstream for very long it causes a lot of damage if you think about what's in your blood it's water oxygen carbon dioxide some other dissolved elements but glucose is pretty big c6h12o6 it's a big ring structure and if you've ever known a diabetic you know that one of the problems is the glucose sticks around in their bloodstream too long and over time it starts to cause damage to all the small capillaries so in their eyes their kidneys fingers toes wherever their tiny little blood vessels it causes damage so our goal is to get any excess glucose that didn't immediately get into our cells for cell respiration we want to get that out of the bloodstream as quickly as possible and that's going to be the job of insulin once we get it out of the bloodstream we want to link it back together and store it so now we're going to have the storage form of carbohydrates in animals and as i mentioned here that is called glycogen glycogen is also a chain of glucose this is how animals link glucose together for long-term storage so glycogen is the storage form of glucose in animals and it is also a chain of glucose just like starches it just it's very branched it does look different from starch where is most of our glycogen stored it's mostly stored in our liver and a small amount in our skeletal muscles so glucose is energy why do you think it would be a good idea for animals to store a certain amount of glycogen in the skeletal muscle why would we need that energy source available in our skeletal muscle remember we're at the top of the food chain for the most part unless you get attacked by a bear or a tiger or something we're mostly at the top of the food chain so we don't need it as much but it's really it's it's fight or flight you want to be able to escape a predator so it's a good idea to have a little bit of sugar in your skeletal muscle so when you eat meat let's say you're eating a steak that is the skeletal muscle of a cow and it's going to have a little bit of glycogen in there so it does have a little bit of sugar in that muscle and when you brown that meat you're caramelizing the sugars that are in that meat there's not much there but there is a little bit because they are storing a little bit of glycogen in the muscle but most of it's stored in the liver so now let's talk about why insulin and glucagon are called opposing hormones let's look at this important diagram okay homeostasis same state in homeostatic mechanisms if this is normal okay this is what we call the set point anytime levels get too high you're going to do something to bring it back down and anytime levels get too low you're going to do something to bring it back up so in a homeostatic mechanism let's say this is our set point so if levels get too high you're going to do something to bring it back down and if levels get too low you're going to do something to bring it back up that's what homeostasis is you want to maintain this constant level for our blood glucose level in most people that's about 90 milligrams of glucose for every 100 milliliters of blood you do not need to memorize that in any way shape or form just know there is a normal level that needs to be attained at all times that's how important it is okay we have all these mechanisms in place for keeping your blood glucose level constant so do you think carbohydrates are important in your diet you better believe they are and this is why you need a constant supply of glucose the only cells in your body that don't require insulin to take in glucose are your brain cells brain cells are different they they obviously are working all day every day that's the master computer you want your brain cells to get the sugar first so they don't require insulin but all other cells of your body require insulin in order to get glucose into your cell so it's kind of the key that unlocks the cell to get glucose in remember it has to be monosaccharide to get into your cells so here's what happens you eat carbs and that's going to cause an increase in your blood glucose level so blood glucose level rises after eating and in response to that the pancreas releases insulin that insulin is going to do two really important things one is it's going to get glucose into the cells so body cells take up more of that glucose any excess is going to get stored in the liver insulin is going to cause glucose to get linked together to form a polymer called glycogen and insulin facilitates that we now store about a four to six hour supply of glycogen in the liver that gets insulin back down to normal i'm sorry that gets glucose back down to normal not insulin let me say that again insulin causes that excess glucose in the bloodstream to get linked together to form glycogen and it's stored mostly in the liver remember again a little bit stored in the skeletal muscle why do we do that two reasons one glucose can't just stick around in the bloodstream it's too damaging we need to store it somewhere but we also want to be ready to release it as soon as we need it so as soon as the blood glucose levels dip so blood glucose level drops after a period of time because we're using it right the cells are using it to make atp as it's getting used we need more so blood glucose levels drop and now the pancreas is going to release another hormone called glucagon glucagon is going to cause us to go back the other way glucagon is going to cause glycogen to get broken down hydrolyzed back to glucose that's why these are called opposing hormones they do the opposite thing so insulin causes glucose to get linked together to get stored as glycogen remember glucose is the monosaccharide six carbon sugar okay glycogen is a chain of glucose in fact it's a branched chain of glucose okay and so on glucagon is going to cause that to get broken back down insulin causes it to get linked back together so as soon as it's broken down it's released back into the bloodstream and we bring our blood sugar back up to normal if you eat an unhealthy diet if you're constantly eating a lot of simple carbs junk food what's happening is rather than having a slow steady release of sugar into your bloodstream you get these big spikes in blood sugar which means you get these big spikes and insulin and you're slamming your cells with insulin in these big amounts and over time your cells become desensitized to insulin what does this mean it means that now you need a larger amount than most people of insulin in order to get glucose into your cells your cells aren't recognizing a normal amount of insulin anymore it's kind of like living by the airport or living on a busy street you first move in you hear the noise you hear the noise you hear the noise over time you don't hear the noise anymore you become desensitized that's what happens to your cells over time if you're slamming them with carbs all day slamming your cells with insulin in these large amounts they become desensitized and when that happens you have what's called type 2 diabetes you usually make a normal amount of insulin but your cells need a larger amount than normal now to get that glucose into your cells otherwise that glucose is sticking around and it's causing some damage very dangerous over time type 2 diabetes used to be called adult onset we now obviously know that a lot of children especially in the united states have type 2 diabetes it's a long hard life if you have type 2 diabetes from the time you're a child type 1 diabetes is something else okay so type 1 diabetes is an autoimmune disorder and what happens is your white blood cells attack and kill cells of the pancreas that produce insulin so you no longer produce enough and usually by about age five you hardly produce any and you have to be on insulin for the rest of your life type two is mostly related to diet you can control type 2 diabetes with diet and exercise exercise pulls excess glucose out of your bloodstream even simple exercise like if an elderly person has some little hand weights and they're sitting and they're moving those hand weights moving their legs pulls excess glucose out of the bloodstream obviously diet is the best way to regulate this as well most type 2 diabetics though if it's long-term they do end up on medications and maybe even insulin occasionally to control that but type 2 diabetes is usually based on lifestyle there are hereditary factors that can make you more likely to get type 2 diabetes but it really has to be a combination of these things so for example i have type 2 diabetes on both sides of my family but i have a very healthy diet and i exercise so i'm probably unlikely to get it but if i did have a poor diet i would be more likely to get type 2 diabetes than the average person but it really has to do both factors have to be there okay opposing hormones insulin and glucagon you should know this story you should know the role of each of those hormones in regulating your blood glucose levels you should know the term homeostasis very very important okay those are storage polysaccharides let me quickly show you glycogen by the way here it is sorry i had to drink some water more branched than starch so you can see starch at the top that's the simple starch and then you can see how branched glycogen is in comparison now we're going to talk about the two types of structural polysaccharide cellulose and chitin here's cellulose very linear in structure has a different shaped bond between the glucose molecules different from starch so cellulose makes up the cell walls of plants again we're going to talk about plant cells in more detail when we talk about cells but this outer part here there's a plasma membrane around the outside of the cell okay and then outside of that is this green part the cell wall and that cell wall is made mostly of cellulose it's a structural polysaccharide why is this significant well if you think about it plants have a lot of cellulose and more um i'm sorry some plants have more cellulose than others in the cell wall so let's think about baby kale versus grown-up kale okay so baby kale the little tiny soft lettuces that you can eat they're in that mixed bag of greens you don't even know them from the other lettuce because they're so delicate if you get a full big old head of kale that stuff is pretty hard to chew because it's higher in cellulose very fibrous in texture we can't go eat grass right neither can our dogs even though they think they can but the reason is it's too high in cellulose it's too high for hard for us to break down we don't have the correct kind of teeth to really break that down mammals who eat a lot of cellulose in their diets have these big broad molars these big broad grinding surfaces so they can mechanically break down part of that cellulose as they're chewing it our teeth aren't like that we have an omnivore diet so we have teeth that can kind of eat meat and kind of eat plants but we don't really do either one very well but if you're if you're an herbivore and you're only eating plants and you're grazing you're gonna have these big broad grinding teeth you're not gonna have any pointy teeth for ripping meat there's an important part to this story no animals have enzymes to digest cellulose and yet if you think about something like an elephant you can build a whole elephant mostly on cellulose how how does that happen okay cellulose is a chain of glucose those animals who have a high cellulose diet they need to be able to break these bonds of the cellulose back into glucose so it can get into their cells as an energy source to build that animal but no animals have enzymes to do that so animals do have enzymes to digest starch so animals have enzymes to hydrolyze starch okay but they do not have enzymes to hydrolyze cellulose the only organisms that do are bacteria and other microorganisms so animals that eat a lot of cellulose have mutualistic relationships a symbiotic relationship with microbes in their gut and those microbes digest the cellulose from them into glucose this is an incredibly important symbiotic relationship in biology so the microbes so bacteria and certain protists have enzymes to hydrolyze cellulose so organisms that have a high cellulose diet have these symbiotic microbes in their gut in fact if you look at a cow or other animals called ruminants they're called remnants because they have this part of their digestive tract called the rumen piece so these microbes that are in the rumen of the gut do have the enzymes to hydrolyze cellulose but the cow doesn't okay so no animals have the enzymes to hydrolyze cellulose they have to have these symbiotic bacteria and protists in their guts to break down that cellulose for them and when that cellulose is hydrolyzed it becomes glucose and becomes an energy source for that animal okay remember they also have mechanical digestion those big broad teeth for breaking down the cell wall of the plant mechanically and then the glucose is released when those microbes digest the cellulose for them okay we can't do that humans we don't have a rumen we don't have these symbiotic bacteria that digest cellulose for us but it becomes something else in our diet i just want to quickly though show you why it's just such a subtle difference in structure if you look at starch and the structure of starch versus cellulose you can see this difference in shape of the bond so see how these hydroxyl groups alternate and you can see the shape of the bond see this one's pointing up and this one's pointing down and then this one's back up whereas these are all just pointing down and you can see these hydroxyl groups are all on the bottom just that slight difference in structure requires different enzymes when we talk about proteins in a unit coming up in a couple of lectures so we're going to do fats next and then we're going to do proteins you're going to see that the shape of those enzymes is very specific one enzyme can only break down one type of reactant so the these two require different enzymes just that subtle difference in shape requires a different enzyme animals can hydrolyze starch animals cannot hydrolyze cellulose okay unless what a mess okay unless they have those symbiotic symbiotic it messes up toward the bottom of the page unless they have those symbiotic microbes the bacteria and the produce and it's just because of that subtle difference in shape so why is cellulose important in our diet it becomes fiber fiber is incredibly important to your health again this isn't a nutrition class but it really does protect your gut it's very protective in preventing colon cancer and other gastrointestinal illness we know that it decreases our blood cholesterol levels it protects our heart it protects your skin your kidneys so fiber is very important in your diet the more cellulose you have the better so eating lots of grains and fresh vegetables and fruits very very important so even though we can't use that cellulose as a glucose source it's very important in our diet okay one last carbohydrate chitin you just need to know about chitin because if you go on to take microbiology you are going to talk about fungi fungi are major pathogens in humans and it does make up the cell walls of fungi and you can see that down here oops sorry cell walls of fungi it makes up the exoskeletons of arthropods so sorry that's written very small so exoskeletons of arthropods so when we say arthropods we mean insects crustaceans millipedes centipedes spiders ticks mites this would sell walls of fungi so mushrooms yeast the spine of diatoms so these are um a type of protist and then there are some other invertebrates that have them shells of mollusks have some chitin along with a lot of minerals so chitin again is a structural polysaccharide it's just important to know about because you'll hear that term especially if you take microbiology and you hear about fungi if you go on to take a major level biology class you will take organismal biology and you will hear about chitin in relation to all of these different animals so those are the carbohydrates that's all