hello biology class welcome back to lesson two i hope you're successful in navigating the first lesson uh and if you weren't if it didn't go so well definitely ask me for help uh but welcome to the second one it seems like you found it this one is titled disaccharide so it is two saccharides or like two monosaccharides put together uh don't worry there's no more structures for you to memorize it's just glucose and fructose that i'd like you to know uh to be able to draw but what you see here you might need to be able to pick out of a lineup let's say to be able to say oh that one is definitely a sucrose or that one is a lactose you don't have to draw them but be able to pick them out you'll notice that that's two of the key points uh sucrose and lactose as well as disaccharides is number one let's get into it we've already started uh come on come on there we go so disaccharides as i said are two monosaccharides bonded together a disaccharide uh some examples are lactose which is found in milk you might be familiar with lactose intolerance which is what our section for you to do is all about and then you've probably heard of table sugar which is sucrose you might not have called it sucrose before you don't say past the sucrose but you might have said past the sugar so that is what we're going to focus on for today what these look like and what these are all about again you can pause here and write down what was on the slide or maybe you paused at the beginning uh you might pause at the beginning of this next slide to write stuff down or you might wait to listen to me talk about it as well what i do want you to do though is take what is on these slides and either info or on you in your own words write down what the most important parts are that will be for you to do in your booklet there's a section for those notes so if you have questions about what i expect from you in terms of what is on these slides definitely let me know but it is all fair game so disaccharides are also called double sugar the sugar is formed when two monosaccharides are joined by what is called a glycosidic linkage so that would be a term that i would take note of we've probably heard of all those other ones up there previous to this but glycosidic linkage might be different so it is what joins two monosaccharides the joining of simple sugars into a double sugar happens by a condensation reaction which involves the elimination of a water molecule as you know when some when water condenses on the side of a glass it essentially is removed from the air and put onto the side of the glass into the form of droplets that's kind of what happens in a condensation reaction water is pushed out and it goes essentially out of the air or out of the reaction so when we join two sugars together we produce water it is the exact opposite when you break a double sugar apart into its two simplest sugars it's called hydrolysis we essentially use up a water molecule so i might pause it here and a couple of things that i might write would be condensation removes a water molecule from the sugars while breaking sugars apart adds a water molecule to them it uses up water which is known as hydrolysis sucrose is a very common sugar it is a disaccharide as we're talking about in this lesson uh it is composed of the two monosaccharides glucose and fructose so whenever a glucose and a fructose come together and a water molecule is eliminated we get a sucrose molecule sucrose is produced naturally in plants and table sugar is essentially sucrose we refine it to get it on its own for human consumption sucrose is extracted and refined from either the sugar cane plant or the sugar beet plant uh there's one of those sugar beet plants in north dakota not too far from us in nature sucrose is present in many plants and in particular their their roots fruits and nectars because it serves as a way to store energy so the sweet parts of fruits contain the sucrose obviously they are sugars and they make it taste sweet so again pause and copy this down maybe not in full you should be able to maybe abbreviate some parts maybe not everything is important to write every single word of it but that is again up to you to decide this is a picture of a sucrose molecule again it is the glucose on the left and the fructose on the right joined together by a glycosidic bond it's called uh again you don't need to draw this you just need to be able to recognize it so if i showed you a picture of a disaccharide and it was a glucose and a fructose molecule joined together then you would know that it is sucrose lactose is a disaccharide as well it is a sugar composed of galactose and glucose so it is made of a familiar glucose molecule and a galactose molecule which is quite similar but we haven't quite talked about yet it's just another six carbon sugar that is made of six rings uh sorry that has a that is made of a ring with six objects in it lactose makes up two to eight percent of milk and it is in dairy products such as yogurt and cheese except it is very little the bacteria that is used to make them consume lactose during the manufacturing process but if you are lactose intolerant that doesn't matter at all a little bit of lactose does cause a problem whether it's yogurt cheese or milk uh this is a picture of the lactose molecules so you can see it's a galactose and a glucose it is two six membered rings which is what i would want you to know uh to be able to pick it out uh sucrose is two uh is a six membered ring and a five-membered ring while lactose is two six-membered rings joined together again you should have these diagrams in your notes below so you can refer to them easily one last thing um is enzymes so enzymes are proteins in the body that perform a whole bunch of different functions one job is to break down molecules into monosaccharides so they float around and when they see a disaccharide they break it up into a monosaccharide so it can be used when you do not have a particular enzyme you can have lactose intolerance so lactose intolerance results when the body lacks the enzyme lactase to break down so it is always the ending being changed to ase that breaks down a particular disaccharide so lactase brings breaks down lactose and sucrase would break down sucrose if you had the ace instead of os you get what the enzyme would be what i'd like you guys to do is i'd like you to do some research and complete the 10 questions that are listed below in your notes about lactose intolerance they are not necessarily revolutionary questions like what um contains what what foods contain lactose what are some symptoms of lactose intolerance what are some tests for it should be easy to find if you guys do have any questions though about what you saw in this lecture or what you need to do for the assignment please let me know and when you're done and you're at school let me see what you've done so i can check you off and we can keep moving on to the next part thanks very much everyone and i'll see you soon