Glucose Transporters (GLUTs and SGLTs) - Biochemistry Lesson

hey guys in this lesson I'm going to be talking to you guys about glucose Transporters what they are uh the different types of glucose Transporters where they are found in the body and their relevance to whole body metabolism so to begin why do we need glucose Transporters well the reason is is because glucose is hydrophilic and as you can see in this depiction of glucose here glucose has many hydroxy groups which makes it very hydrophilic so that means it's not easily transported across cellular membranes so that's why need Transporters so there are actually two types

of Transporters the first type are the glutes or the glucose Transporters and there are actually 14 different types of glutes they are all sodium and ATP independent and they are ubiquitous so they're found all throughout the body in all cell types the other type of glucose transporter are known as the sodium dependent glucose Transporters or the sglts and these are as their name suggests they're sodium dependent and they require ATP because ATP is actually used to form a sodium gradient that is used to transport uh glucose into the cell and they're located in a few

different locations in the body um particularly the intestine Ral tubules and the bloodb Brain barrier so to begin with glucose Transporters um there are actually five very important glucose Transporters in the body glute one to glute 5 the rest of the glucose Transporters um are have not really well been well characterized and there they don't seem to be very um significant to whole body metabolis M so I'm just going to talk to you guys about glute one to glute five so the for glute one um these ones are found in the blood so in red

blood cells or aryes they're also found in the bloodb brain barrier and they're also found in the heart but to a lesser extent so the heart has very minimal amounts of gluten one but uh the blood the red blood cells actually use glute one heavily to uptake glucose and the main important uh key point for glute one is that they are insulin independent so um for instance red blood cells never need insulin to uptake glucose so they always use glucose um even without insulin present so for glute 2 these are found in the liver pancreas

and in small intestine as well and these are also uh insulin independent and they have a high michis mentin constant or high km which means they have a very low affinity for glucose so that means that uh the liver the pancreas and small intestine only uptake glucose through glute 2 when uh glucose trans uh glucose concentrations are very high so this makes sense um a lot of times the liver um will won't take up any glucose it'll let the rest of the body take glucose um for for other usage but the the liver will uptake

glucose through glute 2 when glucose concentrations are very high so it'll up uptake glucose to uh stored as glycogen and the pancreas does this as well with beta cells um beta cells will uptake glucose when glucose concentrations are relatively High which means then um the beta cells will uptake glucose and then the beta cells will will release insulin to uh to compensate for the high glucose level the next glucose transporter is glute 3 this is found in the brain in the neurons and also in sperm um this one is also insulin independent and uh this

the key point with glute 3 is that it has a low michos Menan constant which means it has a very high affinity for glucose so that means that the brain and the neurons in the brain always uh take up glucose and they do it with a high Affinity so if there's any glucose present at all they will make sure that they take up the glucose so um as always the brain um makes sure that it takes up its uh required uh energy uh substrates it make sure that it maintains its metabolism at a at a

constant state regardless of what's going on in the rest of the body so just remember guys that glute 3 has a very um High affinity for glucose which means it's always typically always saturated with glucose and as well it's also insulin independent for glute four um these are found in the skeletal muscle adapost tissue and the heart so as I mentioned before the heart has um glute one as well which is insulin independent and it also has glute four now glute four um actually outnumbers glute one in the Heart by about a 3 to one

ratio so glute four is a little bit more important for heart metabolism than glute one is and the main key point for glute four is that glute four is actually insulin dependent so this is why um insulin actually allows uh uptake of glucose is because it actually acts through glute 4 and again this glute transporter has a moderate km which means it has a moderate affinity for gluc but the main point for glute 4 is that it is insulin dependent so when insulin is released that allows the translocation and uh the the incorporation of glute

four into the cell membranes of skeletal muscle tissue and the heart to allow those uh organs to uptake glucose and the last glute I want to talk to you guys about is glute five and these glucose Transporters are found in ocytes of the intestinal epithelium so in their particularly on the luminal side so they face the Lumen of the small intestines and these are again these are also insulin independent and these are important for fructose transport so they actually uptake fructose um through glute 5 so that means that fructose is always taken up by glute

5 and finally I'm going to talk to you guys about the sodium dependent glucose Transporters so um sglt1 is uh also found in ocytes of the intestinal uh epithelium again this is also on the luminal side so it faces the Lumin of the small intestine and these two are also insulin independent and they are also ATP in sodium uh dependent as uh as they are s sglt and they're important for glucose absorption so typically um glucose is first uptake uptaken into the uh into the ENT sites of the intestinal epithelium um through sglt1 and so

this is the first transporter that glucose typically comes into contact with and sglt2 um is found in the proximal tubule of a nephron so the nefron is the functional unit of the kidney so and these are uh also insulin independent um and ATP and sodium dependent and these are very important for glucose retention so um these Transporters are very important so that you do not lose glucose in your urine so um and this is this comes into play during diabetes when when uh blood levels of glucose are so high that um these Transporters become saturated

and you actually lose um some of your glucose in your urine so that's why you get the you get glycosuria so that's the main reason but the main function of these um Transporters sglt2 Transporters is glucose retention anyways guys that was a quick lesson on glucose Transporters I hope you found it helpful please like And subscribe if you found this video helpful anyways guys thank you so much for watching and have a great day