Carbohydrates

Types of carbohydrates

Features                             Monosaccharides             Disaccharides               Polysaccarides

Type of molecule                 Single                             Two molecules               Many molecules

Solubility in water                Soluble                                Soluble                        Insoluble

No.of glycosidic bonds        None                               One                                 Many

Structure                            Single ring                        Two rings                        Long chains

Roles                                 Energy release       Energy release,storage     Energy storage+structural

Examples                          Glucose,fructose             sucrose,lactose         starch,glycogen,cellulose          

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Monosaccharides: glucose

  • Glucose exists in two forms: alpha and beta
  • H and OH groups are arranged differently on C1
  • Alpha glucose: OH is below C1
  • Beta glucose: OH is above C1
  • Structural differences leads to differences in how they bind to other monosaccharides
  • Most organisms can break down polymers of alpha glucose, but dont have neccisary enzymes to break down beta glucose

Image result for alpha and beta glucose

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Disaccharides

  • Formed of two monosaccharides that join together using glycosidic bond
  • When two alpha glucose monomers join together a 1,4 glycosidic bond is formed
  • C1 of one glucose bonds to C4 of other glucose
  • All disaccharides can be easily hydrolised into monomers to act as an energy source

Image result for 1 4 alpha glycosidic bondImage result for hydrolysis maltose

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Polysaccharides: starch

  • Starch is a polymer of a-glucose molecules
  • Starch is made up of amylose and amylopectin
  • Amylose: a 1,4 glycosidic bonds
  • Amylopectin: a 1,4 and 1,6 glycosidic bonds
  • Structure of starch=ideal storage molecule due to it being compact+stable due to its spring shape
  • Test for present of starch=iodine solution=gives a black, blue colour when starch is present

Image result for amylose and amylopectin structure

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Polysaccharides: Glycogen

  • Polymer of a-glucose molecules
  • Similiar to amylopectin=forms long chains, but there are more branches and chains shorter=compact molecule= 1,4 and 1,6 glycosidic bonds
  • Can be broken down easily into glucose for energy

Related image

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Polysaccharides: Cellulose

  • Made of b-glucose molecules
  • Arrangement of OH and H groups on C1 mean that adjacent glucose molecules only join if alternate molecules are inverted
  • Results in a straight glucose chain with OH groups on the outside
  • Allows H bonds to form between adjacent cellulose molecules=crosslinks=stable structure

Image result for cellulose fibre biology diagram

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Relating structure to function

Carb                Important features               Examples                  Function in organism

Mono              small, soluble                        glucose                   source of energy=easily hydrolysed

Di                   small, soluble                        maltose                   energy storage in some plants

Poly               large, insoluble                      starch                      Energy storage in plants       

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