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Molecular structure of glucose

Video transcript

What I wanted to do in this video is familiarize ourselves with one of the most important molecules in biology And that is Glucose sometimes referred to as Dextrose and the term Dextrose comes from the fact that the form of Glucose typically Typically found in nature if you form a solution of it, it's going to polarize light to the right and Dextre means Right But the more typical term glucose this literally means sweet in greek if you ask a greek friend to say sweet it sounds like Lucas or I'm not saying it perfectly, but it sounds a lot like a glucose And that's because that's where the word comes from and it is super important because it is it is it is how energy [is] stored and transferred in biological systems in fact right [now] when if someone were to talk about your blood your blood sugar they're talking about the glucose content, so when people talk about blood blood sugar they're talking about your they're talking about your glucose content the whole process of photosynthesis this is all about plants using harnessing the [sun's] energy and storing that energy in the form of glucose when we talk about when we talk about things like respiration in our in our cells cellular respiration that's all about taking glucose and using it to full and to create atp's which are the molecular currency of energy Inside of our body, so these are in credit is an incredibly important molecule We can start wreaking chains of glucose to form Glycogen to form Starches this along with another similar another simple sugar fructose you can use to form our table sugar But even glucose by itself is sweet so let's get familiar with it as a molecule so immediately When you look at this is it kind of drawn as a as an open chain we see that we have one two three Actually, let me number these we have one two three four five six carbons, so chemical formula would be C sub six a subscript of six we have how many hydrogen's How many hydrogen's we have we have 1 2 3 4 5 6 7 8 9 10 11 12 hydrogen's? C6H12 and then we have how many oxygens do we have? Have one two three four five six oxygens Six oxygens, so you might notice we have six carbons and then the ratio for every one oxygen We have two hydrogen's which is really the ratio of Hydrogen's to oxygens in Water and if we want to really if we really want to if we add obviously here We don't have just two hydrogen's and one oxygen We have 12 hydrogen's and six oxygens, but it's really good to even just familiarize yourselves with what are the different parts here So we see on the number one carbon it is part of a carbonyl group when a carbon is bonded to double bonded to an oxygen like that. That's a carbonyl Carbonyl carbonyL group and in fact because this carbon it's double bonded to an oxygen, but then it's other bonds are I guess you could say a Carbon chain right over here and then but this other bond right here is a hydrogen we would call this an aldehyde we would call this an aldehyde group and it makes Al Aldehyde and it would officially make the entire molecule an aldehyde if you contain an aldehyde group You are an aldehyde, so glucose and when it's written when it's drawn as a straight chain or it's a straight chain form it would be considered an aldehyde and then Of course it has all these hydroxyl groups on them, and these hydroxyl groups these O-H groups over here That would officially make glucose also it would officially make it an alcohol, and it's neat to keep in mind How the structure is so you have six carbons? One of them is part of this aldehyde group It's part of this carbonyl right over here And then the other five are each bonded to a hydroxyl and what I've oriented it this way four of the hydroxyls are on the right-hand side and the one on the three carbon is on the left-hand side and all of the other carbon bonds are with hydrogen carbon likes to form four covalent bonds every one of these six carbons has formed four covalent bonds And so you would fill up all the rest once you've accounted for this carbonyl here And you've accounted for all of these hydroxyls everything else is going to be hydrogen Now this is when you've drawn when you've drawn glucose just as a straight chain but many times you will see it in its cyclical form It's neat to kind of think of how do you go from this form to this form over here? And so what I've drawn here is this exact same this exact open chain But I've started to I've started to bend it a little bit and just to be able to keep track of things let's renumber The carbons, so this is the carbon. That's part of the carbonyl group So it's carbon one and then we number up from there two three four five And then that is the number six carbon the reason why I've made these this bond over here nice and fat is To show that it's it's kind of closer to us It's popping out of the page and as we go from the the second carbon of the first carbon We're going back into the page when we go from the third carbon to the fourth Carbon We are going we are going back into the page right over here, so this big fat bond. This is between Carbon three and Carbon two, that's this That's this right over here and this going from two to one That's this bond And I'll draw it a little bit kind of going in and then this bond is This bond right over here and so it take a second pause the video if you need but try to orient yourself to orient yourself Imagine we're going to take this to the right like this to bring it over here And then we're going to rotate we're going to rotate this end and bend it up backwards like that To get to this form C six is now bent all the way up is now rotated all the way up there We've bent we've bent this chain and the whole reason is is because this will typically react the hydroxyl group This is it This is the the most typical form of glucose you will see when you see in a sick little form there's actually other forms that You can have but the oxygen that forms a hydroxyl group on the fifth carbon it can it can attack it can attack the the The number one carbon that forms this carbonyl group And that's because oxygen we've talked a lot about it is very electronegative likes to hog electrons So this carbon is partially positive and so you could take one of the lone pairs You could take one of this oxygen right over here. It's going to have two lone pairs Let me just draw them as neatly as I can that's one lone pair, and then this is another lone pair right over here so this oxygen can Form a bond with this carbon when we learn organic chemistry and more depth, we'd call that a nucleophilic attack it sounds very fancy. Just the fact that these are drawn to each other this has a partially positive charge this guy has a lone pairs of electrons that can be used to form bonds with things and so when that when those electrons form this bond or Bond to this carbon that's going to be this bond this Bond right over here And then this carbon can let go this carbon can let go of the electrons in One of these let me do this in a more obvious color and in the double bond right [over] here it could let go of one of the bonds the electrons in one of the bonds and then that can be taken back by the oxygen or even better that can be used by that oxygen to capture a Hydrogen proton in the solution and actually probably part of a Hydronium Molecule But let me just draw it this way this would just be used to capture a Hydrogen proton that would just be a hydrogen a hydrogen atom without its electron. It's just a hydrogen ion It would just be a hydrogen proton and that would form this bond That would form this bond right over here and let me let me just be very clear this carbon this carbon right over here is This carbon right over there this oxygen this oxygen is This oxygen is that oxygen right over there, and so hopefully you see how it forms a cyclone. You're probably saying Oh, wait wait don't we have a little hydrogen attached here isn't the way I've drawn it looks like there's an extra hydrogen over here, and then that would leave this guy with a Positive charge we leave with a positive charge, but you can imagine we're in a solution of water then hey I have some I have another water molecule right over here And you know these things are all bouncing around and interacting in different ways But it could use let me do that in the right color it could use So that's oxygen it could use one of its lone pairs instead of this you know this will become positive temporarily But then it can use it can do it can use one of its lone pairs to grab just the hydrogen proton which would allow Which will allow this character to take its to take its Electrons to take these electrons back and turn into this character and just be neutral and then this this guy Would have gained so we have a proton going into the solution you have hi But we took a proton from [the] solution We took a proton we gave a proton to the solution And so you could end up with this so the whole reason I did This is [just] so when you see it in biology class or chemistry class you're not intimidated by it in fact This is something that's really valuable to get very very familiar [with] because you're going to see Glucose and other sugars in many many many different molecules throughout your academic career