Gastrointestinal | Digestion & Absorption of Carbohydrates

I ninja nerds in this video we are gonna talk about the digestion and the absorption of carbohydrates so let's go and get started so let's imagine for a second we take a scenario where we're going to ingest a particular food substance that's rich in carbohydrates and for example here I love pizza pizza is awesome it's amazing it's delicious and what we're gonna say a part of the pizza is like the crust specifically the crust and the bread part of the peas is going to be the part that's rich in carbohydrates but another question you should

ask yourself is out of this what are the most significant parts what are the actual carbohydrate molecules that are in that pizza that we want to digest there's a bunch of them but we're only going to primarily focus on two significant types one here is this big one here and this big maluhia molecule here is called amylopectin and we'll talk about this one in a second and the other one is this linear molecule called amylose there is another one that we can digest from substances that are like fruits and veggies and that's called cellulose and

there's other ones like chitin and lignans but again we're primarily going to focus on the ones that are actually going to be absorbed cellulose is actually not able to be broken down and absorbed because we don't have the enzyme cellulase so because of that cellulose which is a part of the different plants and veggies really it's just a part of our dietary fiber and so that helps with you know increasing the stool size and helping with easing the actual bowel movements and there's also been other health benefits to of it that they say that it

can control the bacteria metabolism like the prebiotic mechanisms and they can play a role in insulin controlling an insulin release all right anyway getting back to this let's say that we ingest this pizza pizza and in the piece of pizza there is rich amount of amylopectin and amylose what I want you to realize about this diagram is that this big big brown tube here we're gonna represent as our GI tract but we're going to go through parts of the GI tract where the different digestive ends are going to be found that's why we have these

little tubes here so if you imagine this tube this tube is going to be specific to like the oral cavity so let's say that this tube is really really specific to the oral cavity okay and this is actually going to be the next one which is going to be respect with the pancreas now the pancreas makes different types of enzymes like pancreatic amylase and that gets released into a specific part of the GI tract around the area of the duodenum okay and then the last part here is we're gonna zoom in on a these entero

sites so these are going to be this is one gargantuan santero site with a bunch of these different brush border enzymes and this is the part where we'll focus on different types of disaccharide enzymes as well as a couple other different types of ones here and then we'll talk about the absorption of these monosaccharides and then the movement be at the a patek portal system to the liver alright so let's go ahead and get started so the first enzyme that we want to focus on here is going to be secreted by this gland and this

gland here is going to be our salivary glands there's a bunch of these bad boys so salivary glands you have extrinsic and you have the intrinsic salivary glands you know like the parotid is an extrinsic or the submandibular or the sublingual and then there's the intrinsic like the lab you'll the Palatine the bucco glands but they're making different types of saliva now the saliva mainly from the extrinsic salivary glands is rich in a particular enzyme and that enzyme is going to help in the chemical digestion of this amylopectin and amylose what is that chemical right

here that chemical that we're going to focus on here is going to be what's called salivary alpha amylase and realize there is another name for it just in case you read it it's also called ty Alan all right whoops Helen get the a there in the middle ayan okay so these are the different this is the special enzyme that we're actually going to release out here into this part of the oral cavity now let's say here's the tube this is going to be like that duct that we're gonna release it in and if it's via

the extrinsic salivary glands now once the salivary enzyme salivary amylase is out here let's treat him like a little pac-man I like I like a little pac-man little guy this is our salivary amylase now this salivary amylase he is hungry and he is going to come and start digesting certain types of chemical bonds on these carbohydrate molecules but in order for us to really understand this what I wanted to do is just very very briefly this is not a biochemistry video I need to very very briefly talk about just a little bit about the chemical

structure of these monosaccharides or together these polysaccharides so let's come down here for just a second so we can get a tiny little view here on the one of these monosaccharides so if you look at a monosaccharide it's a six carbon sugar in this situation and i'm gonna show you where those carbons are so that we have some understanding of what these bonds are because that's the important point so here is going to be this monosaccharides now on this monosaccharides we have six special carbons the carbon that's close to the oxygen here that is carbon

number one come down here and start just doing a circle go clockwise this is carbon two carbon three carbon four carbon five and here is going to be carbon six there's two types of bonds that we are going to see in these different types of carbohydrate molecules okay and what are some of these bonds we're going to see one type of bond it's going to be between the four carbon of this guy and the one carbon of another glucose molecule so for example let's say I take this glucose or monosaccharides it should be specific and

have it bonded to another guy over here so now I'm gonna have this this is usually a hydroxyl group now same thing here this is the four carbon of this monosaccharides this is the one carbon of that monosaccharides and then again two three four five six this bond right here between the one carbon of this guy and the four carbon of this guy it's a special type of bond what is the name of this bond this bond is called a alpha one to four glyco siddik bond that is the name of this bond okay then

we have another one let's that bring one more glucose ma one more monosaccharide out here one more out here and I'm gonna go here here oxygen and again put my ch2 and then my age group here but it's gotta H is gonna leave here in a second same thing here one two three four five six there's another bond that we can do this next bond is I'm going to attach another glucose unit onto this part here so now you actually do keep the oxygen here and then you get another molecule and then look right here

is the six carbon here so now if you remember this is the six carbon of this monosaccharides that is the O it's next to the oxygen that's the one carbon this is the two carbon this is the three carbon that's the four carbon five carbon six carbon now this new bond that we just formed the new bond is between the one carbon of this monosaccharides and the six carbon of this monosaccharides so now what is this bond that is between these two molecules that bond right there this one right here between the 1 and the

6 let me kind of circle it like this this is called a alpha 1 to 6 glyco siddik bond and the purpose of the alpha 1-6 glycosidic bond is to allow for the branching of these different types of polysaccharides so now we should understand a little bit a tiny tiny bit necessary for us to understand this actual structure here and what type of bonds this enzyme is going to break so now that we understand these bonds what I want you to realize is that amylopectin as you can see here look what kind of bonds he

has he has this part that are linear going from 1 to 4 so he has a bunch of alpha 1-4 glycosidic bonds so he has 2 different types of bonds here he has alpha 1 2 4 glycosidic bonds and he has these branching points right here and right here those are his alpha 1 to 6 glyco acidic bonds now that is the difference between amylopectin and amylose because what can you see here with amylose amylose only has 1 4 glycosidic bonds so amylose only is containing alpha 1 2 4 glyco acidic bonds alright sweet deal

what salivary amylase does is he only targets the 1-4 so what he's going to do is he's gonna come over here and he's gonna try to break this bond he's gonna come over here and he's gonna try to break this bond and this bond and this bond and this bond and this bond so he is gonna start destroying some of these things so he's going to start breaking the alpha 1-4 glycosidic Bonz now when he does that when he breaks this amylopectin and he's also gonna break this bond over here so here I'll bring the

little Pacman do down here - there's my little pac-man guy my little salivary amylase he is going to break again these alpha 1-4 glycosidic bonds now when he breaks the alpha 1-4 glycosidic bonds he's gonna break the majority of this amylopectin and the majority of this amylose into another different type of molecules these three special types of molecules we're gonna represent here one is called maltose so one of the molecules that we can get a lot of is we can get what's called maltose another one that we can get a lot of is what's called

Malto triose so another one here is going to be what's called molto triose this is Malto triose and then we get one more and the big difference with this one is that he has to have those branching points and if you remember those branching points what was specific it had to have those alpha 1-6 glycosidic bonds so off of here I'm gonna have a couple branching points here let's just do it like this and then one more here so now I have this molecule and this molecule is called my alpha limit dextrans so my alpha

limit dextrans okay so here's what I got I have my Malto triose from the break down here I have my maltose and I have my alpha limit dextrans we're gonna refer to these molecules primarily multo triose and alpha limit dextrans usually when you have three or more different monosaccharides we call them oligosaccharides and if you only have two of these monosaccharides you refer to as disaccharides alright so the next thing it's really interesting is the salivary amylase if we know it's made by the salivary glands and pushed into the oral cavity but not all of

this carbohydrate digestion is occurring just in the oral cavity that's the thing food isn't really in our oral cavity that long for me it's definitely not because I'm swole noon to talk to them suckers hole alright so that's important to understand that this chemical digestion of carbohydrates isn't really just happening only in the oral cavity it's actually happening and all the organs on the way to the stomach so if you think about it when we swallow the food via deglutition it moves down through what other structures pass the oral cavity it moves past what's called

the pharynx and then it can move into the esophagus and then it moves into the stomach now you have to remember that the stomach is super super super acidic in salivary amylase his enzymatic activity is it is optimal with an acidic range but not super super acidic guys in the stomach so it doesn't literally last very long in the stomach but it does allow for some chemical digestion to take place I want you to remember though the salivary amylase doesn't account for a super super large amount of the actual chemical digestion maybe 10 to 15

percent of the actual chemical digestion of polysaccharides is occurring by the action of salivary alpha amylase the next enzyme is also going to be contributing a decent amount here to the breakdown of amyl packed in and amylose and what is this molecule so if we go to the pancreas we talked about this these molecules specifically when we talked about the intestinal phase of gastric secretion but if you remember we had like a ballooned out area here and this ballooned out area was consisting it was called the ascent and the ascend I you had your ascend

our cells and the ascend our cells made a bunch of different types of digestive enzymes one of them was called pancreatic amylase so now pancreatic amylase salivary amylase be thankful they pretty much do the exact same thing so now we're going to secrete the pancreatic amylase into the duodenum because you know really what happens is you have the gallbladder and the gallbladder has what's called the common bile duct and the common bile duct comes down and fuses with the main pancreatic duct informs the apat of pancreatic ampulla and then what happens is based upon a

hormone you know there's a hormone called Coley Sisto Kynan he acts on what's called the hepatic pancreatic sphincter or the sphincter of Oddi and triggers the relaxation of that muscle to lead to the ejection of this pancreatic amylase not only that but a beautiful thing here is C CK is so nice he says not let me help you out also too I'm gonna stimulate the pancreatic ascend I to make pancreatic amylase also but again remember what does pancreatic amylase do pancreatic amylase look we're gonna draw him like this there's this guy this guy is going

to do the same thing we're gonna represent it here in this orange he's going to cut specifically only 1 and 1/2 for glyco siddik bonds when he breaks the alpha 1-4 glycosidic bonds he's just going to increase the digestion of amylopectin and amylose so here into maltose multo triose and alpha limit dextrins so that is the function of this little cool little enzyme and this is called pancreas annik amylase this little dude here and then this maroon guy here is our salivary amylase so beautiful thing beautiful thing alright now we go down here to where

we're still in that we can begin the duodenum the jejunum the ileum and so pretty much the entire intestine because in taro site is gonna be for your intestines primarily that of the small intestine so let me actually put back this is an entero site but primarily of the small intestine a lot of the ins or absorption occurs primarily in the small intestine very very little things that are absorbed in the large intestine mainly water and electrolytes okay so now we have a bunch of different enzymes here's what we get to these guys you see

these guys they're literally bordering this actual enterocyte these enzymes are referred to as brush border enzymes so let me write this over here we have what's called brush border enzymes and there is a four types that we are going to discuss one is going to be lactase another one is going to be Maltese another name for it is called glucoamylase another one is going to be sucrase and there's another one which is called ISO Maltese but what you're going to see very interestingly is that sucrose and isomalt taste are actually complex together as one big

big enzyme but made up of two individual components which is pretty cool now one more thing about the brush border enzymes is I didn't represent it here but when you look at inteiro sites your small intestine cells they actually have the small little cytoplasmic extensions and these little small cytoplasmic extensions are really important for being able to increase the surface area not just for chemical digestion but also for absorption what are these little cytoplasmic extensions called they call them micro villi and what's so cool I didn't represent here but this microvilli these enzymes I'm gonna

represent here's blue that's the lactase enzyme that we're gonna talk about and then over here we'll do red that's going to be the next one which is going to be the maltase enzyme and then after that we can have the sucrase and the isomalt taste enzyme and again these are also going to be over here too so the whole point that I'm trying to get across here is that the microvilli are the ones that contain a high concentration of these brush border enzymes and the whole purpose of the microvilli to remember that is to remember

that it increases the surface area for chemical digestion and absorption so for digestion and absorption so that's pretty cool there's other structures in the intestines that also increase the surface area for digestion absorption like the pluck a circulars and another one is the intestines we'll talk about this when we talk about the histology of the GI tract but generally when you look at your intestines they have like this type of structure they come around like this and what happens is the intera sites are actually covering these things and that's where you get those little micro

villi here but these little hills where the actual antara sites are sitting on these hills are called villi okay so these are called your intestinal villi okay that one is just a villus but you have a bunch of these which they're plural it's called a vill I your intestinal villi so you have intestinal villi you have micro villi and another thing called plaque a circular or circular folds and they all help to increase the surface area for digestion and absorption in the small intestine all right cool so now we're gonna do is these are the

big things that you're gonna get released here all right these maltose multo trios awful limb addictions but there's other things that can be released here too these are just one of the significant ones another thing that can be released here is what's called lactose okay lactose in lactose is just a disaccharide it's a 2-car to glucose and galactose unit basically and what happens is here I'm gonna put Glu for glucose and gal4 galactose these are the two components of the lactose molecule the lactose molecule is going to run into this blue enzyme and what is

this blue enzyme called this blue enzyme is called lactase some people might know about this enzyme because you might not have it sometimes in genetic situations you don't express this enzyme or maybe due to environmental stimuli you actually inhibit the production of this enzyme and if you don't have this enzyme guess what you can't break down you can't break down lactose so you can't eat any type of substances that have lactose in it which is commonly substances with like dairy so milk and cheese and different stuff like that because it can cause severe diarrhea cramping

you'll be you know tootin a lot too so that's significant done to know a little bit about that so here's what happens the glucose and galactose molecule the lactose together they come in and they fit into this little active site of the enzyme so looking I'm gonna put it like this so here's boom-boom-boom-boom-boom here's that guy and we're gonna bring it together here like this now what happens is as the lactase is going to break that bond it's gonna break the glycosidic bond between glucose and galactose once you do that guess what you do you

break this bond here by breaking that bond right there it is going to separate these two guys into their individual components and what are these individual components we're going to represent them as circles now this is going to be glucose and this is going to be our galactose so will put Glu and ga-oh here all right cool that's an important thing to know that is the job of lactase it breaks down lactose if you break down lactose you break it into two components and it is going to be glucose and galactose all right sweet that's

it now we come to the next enzyme this red enzyme this red enzyme is a very special enzyme he is called Maul tace and again another name for maltese I'll write it over here is called gluco amylase that's another name for maltese as glucoamylase what it can do is is it can take maltose right so he can take maltose it can take Malto triose and it can break these puppies down now here's the thing maltose is actually going to be made up of two glucose units so now here's what I'm gonna do I'm gonna put

again in here another little thing here here's a little guy here and here's another guy right here I'm just doing the maltose here but I realize that Malta triose will have pretty much the same thing here and what I'm gonna do is is if maltose or multo triose fits in here guess what's going to happen maltose is going to be made up of two glucose units so when you break the bonds the glycosidic bond between maltose it's going to break this off into two components one component is going to be the glucose and the other

component is going to be the glucose that's such a cool thing there so maltose is two glucose units whereas lactose is a glucose and galactose now we come into this next one this double enzyme if you will this enzyme we said that there are two parts so here's what we need to do here the pink part is called sucrase but they're combined together this part here is called ISO maltese here's what is cool about these enzymes sucrase it can take on maltose it can take on Malta triose it can take on alpha limit dextrans but

what it does is it also functions in breaking down another molecule and that other molecule is called sucrose so now let me put in here a sucrose molecule so here's one I'm gonna bring this over like this ok now this molecule here this right here is called sucrose but again it can break down it can break down maltose it can break down Malto triose and it can even break down a little bit of the Alpha lemma dextrins but the Alpha lemma decsions is primarily for this enzyme and that's what we'll talk about here but now

sucrase is really gonna love to digest this sucrose if it digests the sucrose it's gonna break the sucrose down into two components and what are these two components that we're going to get out of here so one component that we'll get out of the sucrose is going to be glucose the other component is going to be fructose so now as a super-fast recap lactose breaks down a lactase breaks down lactose into glucose galactose maltase breaks down maltose into two glucose molecules and Su sucrase breaks down sucrose into glucose and fructose but realize that sucrase can

also act on maltose and multo triose the last one here is the isomalt taste like I told you the isomalt ace is very very specific he loves he loves to break down alpha limit dextrins so now what this isomalt ace does is he's really good at breaking down the Alpha limit dextran so here let me put this here so I have more room here in this active site here of this enzyme now what I'm gonna do is I'm gonna take here and I'm gonna have a glucose molecule or you know a monosaccharide I'm gonna have

them like this and they gonna remember you have that six carbon popping up here and they're coming off of this I'm going to have my glucose from the unit's right here or my - saccharide units now remember we said that this bond is the special bond right here these two bonds these two bonds right here are the Alpha 1-6 glycosidic bonds isomalt ace is one of the special special enzymes that primarily targets the Alpha 1-6 glycosidic bond so now look at this we're gonna kind of fit this like that way yeah and then we'll have

another part of this enzyme like this so we'll kind of bring the enzyme like this a little bit way yeah all right so now if you look at it what is this going to do the whole purpose of this is I'm going to break the Alpha 1-6 glycosidic bonds by breaking this bond the Alpha 1-6 glycosidic bonds it breaks down the Alpha 1-6 glycosidic bonds which helps all these other different enzymes mala taste lactase sucrase to continue to break the 1-4 glycosidic bonds so that is what is so cool about this guy is that whenever

this reaction happens it breaks down these alpha limit dextrins and when it breaks it down it gets rid of those alpha 1-6 glycosidic bonds and as a result it might release out of here some glucose it might even release out of here some other molecules too but we're gonna primarily say here that it's going to be glucose because that's the main monosaccharide that we want to absorb all right so now lactase broke down lactose glucose galactose maltase broke down maltose and two two glucose units sucrase broke down sucrose into glucose and fructose but the isomalt

ace was that really special one and the reason why it was really special is because it was break the alpha-1 6 it was breaking alpha 1 to 6 glyco acidic bonds and remember that as it were is breaking that alpha 1-6 glycosidic bonds that again is going to help all of these other enzymes to continue to break down these oligosaccharides or disaccharides and to their individual monosaccharides units so now we are pretty much ready to absorb these puppies here's the cool thing there's two main mechanisms that we're going to get all of these sugar units

in fructose is a really cool guy because fructose says you know what I don't want to go with glucose and galactose I want to go on my own so here I'm gonna have this pink guy here and this is going to represent our fructose fructose has a special channel that will facilitate his diffusion from the intestinal time in this case or the lumen of the small intestine into this inteiro site do you know what this protein that is going to help and his facilitated diffusion is called this protein is called glut 5 so it's a

glucose transporter type 5 and it's going to transport the fructose from the intestinal lumen into the inteiro site oh that's cool alright so that's going to be by facilitated diffusion the other guys aren't so lucky they're going to be going against their concentration gradient glucose and galactose so here's the thing on every cell in your entire body you have these special protein molecules these protein molecules are constantly pumping 3 sodium out of the cell and pumping 2 potassium ions into the cell and this process is requiring the utilization of ATP into ADP and inorganic phosphate

right because it's utilizing energy this is an example of primary active transport we're pushing the sodium against its concentration gradient and pushing the potassium against this concentration gradient but by doing that pushing the sodium out what happens to the concentration of sodium inside the cell it's going to decrease well guess what it decreases so much that the sodium concentration in the actual intestinal lumen is much much higher than the concentration of the sodium inside of the cell so sodium says hey glucose hey galactose you guys can follow me and if you follow me I can

get you guys into the cell because I've already helped out in this process so sodium comes into the cell and as a result glucose and galactose will follow so here I'm going to have glucose and here I'm also going to have galactose and again what molecule did we bring in here we brought in sodium and guess what we can do with that sodium we can shut it out again through that sodium potassium ATPase transporters so this right here is through an SG LT transporter they call this transporter the s glt sodium glucose transporter that's literally

what they call it they call it a sodium-glucose cotransport ER and that's pumping the sodium into the cell and pumping the glucose and galactose into the cell so it's a symporter technically right but again the reason why it's doing that is because it was able to sodium is able to move down his concentration gradient and bring glucose and galactose with it via what's called secondary active transport now here's the cool thing we have fructose we have glucose and we have galactose these guys right here are our main monosaccharides so glucose galactose and fructose these guys

right here are our main mono saccharides this is the big ones that we want here's the cool thing on the basolateral membrane the part where we're actually gonna have the blood right so this is the lumen side this is the actual basal lateral side where the actual blood vessels will be right here you're gonna have these blue transporters and these blue transporters are really cool these blue transporters are actually a glut transporter but primarily glut - so these right here are called glut 2 transporters this one right here and this one right here the got

two transporters are nice because they're not too specific to just glucose they're also can take on fructose they also can take on de lactose and they can also take up glucose too now we're gonna have here Boop and we're gonna have here so from here what am I gonna have coming out here and going into the actual blood I'm going to have glucose I'm going to have galactose and eventually coming up underneath it here I'm even going to have fructose what will happen is these guys will get absorbed into the actual intestinal veins here so

there's some actual capillaries and what will happen is these guys will get taken up by the intestinal capillaries on the vein side of it and they'll actually get absorbed and taken up eventually through different types of beans you know there's the superior mesenteric vein there's the inferior mesenteric vein there will write all this down here so what happens is you have a bunch of different veins we're going to call this vein as collectively we're going to call it the a patek portal vain but there's a lot of different structures that are going to be incorporated

into this will have another video when we talk about the liver lobules but we are having a bunch of different structures like the superior mesenteric vein the inferior mesenteric vein the gastric veins the splenic veins and even the pancreatic veins which is important because we need insulin to help in this process here so all of these guys are coming together to form the hepatic portal vein and what the a patek portal vein is going to do is it's going to take this glucose and it's gonna take that it's gonna take the glucose it's gonna take

the galactose and it's gonna take the fructose and perform certain types of metabolic activities primarily since we're feeding we're gonna do what's called glyco Genesis we're gonna do other processes like maybe even some glycolysis so that is going to be important and we'll talk about again this in more detail when we talk about the liver lobule ina engineer so I hope all of this made sense I hope that you guys really did enjoy it if you guys did I'm begging you please hit that like button comment down in the comment section and please subscribe also

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