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Main content
Current time:0:00Total duration:4:28
AP.BIO:
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Video transcript

what we're going to do in this video is give ourselves a quick introduction to carbohydrates and you might already be familiar with the notion if you look at a some packaged food there's usually a nutritional label and we'll say carbohydrates it'll tell you a certain number of grams per serving and not all carbohydrates are edible but many of the things that we eat or many carbohydrates are edible and many of the foods we eat have some carbohydrate component to it but what's actually what is it actually well we can look at the word and we see carb oh so maybe it has something to do with carbons and it says hydrates so maybe it has something to do with water and if you said that you'd be pretty close because carbohydrates do involve carbons in fact this is a very typical carbohydrate a very simple one right over here this is a glucose molecule and in gray you see that it has six carbons and the hydrate part refers to that carbohydrates typically have oxygen two hydrogen's in the same ratio as you would expect in water so for every one oxygen two hydrogen's and you see that right over here we're in glucose you have one two three four five six oxygens and you have 12 hydrogen's and so this that's where this word comes from now another word that is often used interchangeably with carbohydrates is a term saccharide sac all right and saccharide comes from greek for sweet and that makes sense because if you were to taste glucose it would taste sweet to you now what's interesting about something like a glucose is glucose can be a standalone molecule a very simple sugar in this case or you can build up larger molecules with really glucose as a building block so for example right over here we have a part of a glycogen molecule and as you can see it's just a repeating sequence of glucose molecules and so something like this we would call glucose a monosaccharide it's one simple sugar right over here mono saccharide and we would call this glycogen a polysaccharide poly poly Sakura or another way to think about it is glucose is the building block for the glycogen another term you might see is monomer and polymer those are the general terms of if I'm building a large molecule out of a chain of smaller ones the building blocks we would consider to be monomers and then the thing that we build out of those monomers could be our polymer and as we'll see this monomer polymer phenomenon is not limited to carbohydrates or saccharides we're going to see that same relationship for example between amino acids and proteins now what role do carbohydrates play inside of biological systems well saccharides or carbohydrates are often associated with a source of energy glucose can be converted very quickly to energy in biological cells glycogen is also a store of energy in your liver and your muscles and once again it can be broken down into the glucose molecules which once again is a very readily available source of energy now in plants especially some of these polysaccharides could also play a structural role if we're talking about things like cellulose which is another polysaccharide so there's also a structural role now I will leave you there we have focused only on one type of monosaccharides in glucose and only on one top-up type of polysaccharide in glycogen as we will see glucose does show up a lot but there are many other types of monosaccharides and there are many other types of polysaccharides and polysaccharides in particular are part of a broader group of molecules known as macro molecules and as you can imagine from the macro prefix it's referring to large molecules oftentimes that have thousands of atoms in them but don't get the wrong idea they're very large at an atomic level but each of these circles are still atoms so you would still need a very very very very powerful microscope to even take a look at even some of the largest macro molecules including polysaccharides
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