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September 5, 2019

Carbohydrates are biomolecules that are composed of carbon, hydrogen and oxygen atoms in the ratio of 1:2:1. We can represent the proportion of these elements within carbohydrate molecules with the formula CH2O. Most carbohydrates are characterized as either monosaccharides, disaccharides or polysaccharides. The term “saccharide” is just another word for sugar. The prefixes mono, di and poly refer to the number of sugars in the molecule. “Mono” means one, so a monosaccharide is a carbohydrate made of one unit of sugar. The prefix “di” means two, so a disaccharide is a carbohydrate made of two units of sugar. And “poly” means many, so a polysaccharide is made of many sugar units bonded together. Let’s talk about monosaccharides first. Monosaccharides are the building blocks, or monomers, of all carbohydrates. Common monosaccharides include glucose, fructose, and galactose. Glucose is by far the most abundant monosaccharide. It is water soluble, easily transported through an organism, and is the energy source for cellular respiration and the production of ATP. Fructose is the primary monosaccharide found in fruits and plants, and galactose is the primary monosaccharide found in milk. All of these monosaccharides are six carbon sugars with the chemical formula C6H12O6. They can be depicted chemically as either straight chains or rings. Disaccharides are formed when monosaccharides are joined together through dehydration reactions forming glycosidic linkages. Common disaccharides include maltose, which is made up of two glucose molecules; sucrose (also known as table sugar), which is made up of glucose and fructose; and lactose (or milk sugar) which contains glucose and galactose. Polysaccharides are formed when glucose monomers link together to form long chains. These long chains of glucose units are ideal for storing energy. The chains can be straight or branched. Plants store energy in the form of amylose, which has straight chains, or amylopectin, which is branched. Animals differ from plants in that they store energy in the form of glycogen, which is a highly branched polysaccharide that can be broken down quickly to supply energy to tissues. Other polysaccharides such as cellulose, chitin and peptidoglycan serve as structural molecules in organisms. The most abundant polysaccharide is cellulose. Cellulose is a straight chain polymer of glucose like amylose, but it differs in the configuration of the bonds between the glucose units. Most organisms are unable to break these bonds and cannot use cellulose as a source of energy. Instead cellulose is used to add strength to plant cell walls. Chitin is a structural polysaccharide found in animals and fungi. It makes up the exoskeleton of insects and crustaceans. Its unique properties are a result of chitin having amino groups attached to its sugar monomers. Peptidoglycans are complex polysaccharides found in the cell walls of bacteria. The macromolecule is both flexible and rugged due to its structure. Each monomer of the polysaccharide has a peptide chain attached to it. Often, we refer to carbohydrates as being either simple sugars or complex carbohydrates. Monosaccharides and disaccharides are commonly referred to as simple sugars. The term complex carbohydrates refers to the polysaccharides.

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  • Reply RicochetScience November 5, 2015 at 3:49 pm

    This is a new version of the video (added on Nov 3rd) that corrected a closed-captioning error. Thanks!!

  • Reply Jimmy Hira January 11, 2017 at 12:05 am

    Thanks for making the video

  • Reply مرتضى علي March 3, 2017 at 8:37 am

    Thank you

  • Reply amber Jenkins March 8, 2017 at 9:54 pm

    Thanks for the video

  • Reply Narendra Choudhary March 9, 2017 at 1:38 am

    thank u for this vdeo

  • Reply indian fashion March 11, 2017 at 4:27 pm

    not bad

  • Reply Tiffany Davis April 9, 2017 at 8:24 pm

    This helped me out big time.
    Thank you!! 😊

  • Reply Mospac Phliem August 27, 2017 at 8:44 pm


  • Reply Math You Forgot September 24, 2017 at 9:19 pm

    These are very helpful videos but the "S" sound is a very high pitched squeal. It makes it difficult to listen. You can fix this in most video authoring softwares. Carbohydrate is also misspelled in the description.

  • Reply Vini Verma October 26, 2017 at 1:56 pm

    thanx for making this video. This video are very helpful

  • Reply GnLEliteCombat PvP November 22, 2017 at 5:45 pm

    greetings from RWTH in Aachen, Germany 🙂

  • Reply Nabin kumar Adhikari November 23, 2017 at 2:33 am

    Easy to understand

  • Reply Orlando Calud January 8, 2018 at 11:14 am

    He he he EDI WOW

  • Reply RaGhu Va RaN April 5, 2018 at 12:45 pm


  • Reply Syamala Ragolu April 7, 2018 at 3:49 pm

    Thank you for your class

  • Reply Liceo Internazionale S.Alessandro May 3, 2018 at 2:23 pm

    thanks! it was really helpful 🙂

  • Reply Nad Douglas June 25, 2018 at 10:17 am

    I'm in university and have a sectional /quiz shortly on the macro nutrients and this video saved me the hassle of reading the chapter in the book on carbohydrates. One chapter down in less than 5 minutes thanks to you.

  • Reply THE GRIMLOCK'S SHOW July 3, 2018 at 4:56 pm


  • Reply Mazhar Hussain August 23, 2018 at 8:24 am

    Thanx nice video

  • Reply مقاطع فيديو September 5, 2018 at 11:39 am

    كتير حلو

  • Reply Pooja parmar September 10, 2018 at 5:38 pm

    Mind blowing🙏

  • Reply Christopher Nyakundi September 18, 2018 at 6:39 pm

    wtf is this whistling in my right ear

  • Reply Ruata Fambawl October 5, 2018 at 4:58 am

    easy to understand . thank you… it helps me alot

  • Reply Nut October 16, 2018 at 12:14 am

    I appreciate the video and it's a great resource but there is some artifacts in the video that make it hard to listen to.

  • Reply talking taco November 12, 2018 at 5:47 am

    thank you!!!

  • Reply NEON WOLF November 14, 2018 at 1:03 am

    Who are here after reading the chapter in all in one?

  • Reply Abhishek Pawar January 2, 2019 at 10:54 am

    Very good

  • Reply Shaday White January 29, 2019 at 8:23 pm

    WOW! This is what I'm talking about, watch me pass Bio 121!

  • Reply Vipin Rathore February 2, 2019 at 5:30 pm

    Please makes the viedo of reactions of glucose fructose etc plz plz

  • Reply Adam Quiroz February 13, 2019 at 7:30 pm

    fix your mic my ears are bleeding

  • Reply DrPugjunior February 18, 2019 at 11:37 pm

    i just nut

  • Reply Viral On YouTube March 9, 2019 at 4:44 am

    Hmm…😃 I'm impressed with your way of covering this topic in just 4 mins. This is tremendous. I liked it. Due to which, Guess what? I subscribed to your channel. You know! It's very difficult for any educational channel to impress me..But you excelled. Good Work! Keep it up!

  • Reply Valerie .M March 31, 2019 at 10:22 pm

    This video is AMAZING!! Thank you so much!

  • Reply Brandon Oon April 21, 2019 at 2:16 pm

    the ring form of fructose is wrong thr are 7 oxygen atom in the molecule

  • Reply Matthew Black May 14, 2019 at 7:22 am

    Great video! Fructose is a pentose sugar while glucose and galactose are hexose sugars, they aren’t all 6-carbon sugars

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