14GLUCOSE comes in 2forms, according how the ring closes. For example, this one:Here this H is abovethe carbon.This is called (alpha)glucose.
15Here this H is below the carbon. This is called β (beta) glucose. WARNING!A single detail like this one makes all the difference.The position of the OH group on C1will determine the type of polysaccharide it will formand in turn, the functions it will have in a cell.
16Structural Isomers Both these molecules are glucose. Both have a molecular formula of C6H12O6.But they are structurally different and will havedifferent functions in a cell.
17Biological role of monosaccharides As an energy source…..A large amount of energy is stored between the C-H bondsThis is released to form ATPATP is the energy currency of the cellAs building blocks…..Repeated glucose molecules build up; starch & glycogenRibose (5C) forms part RNADeoxyribose (5C) forms part DNA
18Forming a disaccharide… …MALTOSETwo glucose molecules meet.The OH from C1 & H from C4 react.Water is expelled. This is called a condensation reaction.The bond between the two joined glucoses is called glycosidic bond.
19Polysaccharides Polymers with subunits of monosaccharides Repeated condensation reactionsNormally thousands of monomers longPolysaccharides are not sugarsSTARCHCELLULOSEGLYCOGEN
20Starch Polymer of glucose. Plant storage polysaccharide. Made up of two types of substances;Amylose 2) AmylopectinAmyloseCondensation reactions between α glucose(1-4 links).Forms from 1000s of condensation reactions.Coiled springs are formed.
25Starch grains are a mixture of amylose & amylopectin Starch is a polysaccharideStarch it is a insoluble store of glucoseStarch is only found in plant cells, the animalequivalent is called GLYCOGEN.
26GLYCOGEN is the storage polysaccharide in animals It has 1-4 linksand 1-6 links
27Cellulose Present in plant cell walls. Has a slow decomposition. It is the most abundant organic molecule on the planet!!It is mechanically very strong.It is a polymer of β glucose
28Cellulose C1-4 links make up this polysaccharide. If C1 and C4 are to react, one glucosemolecule needs to flip through 180o.It is this subtle difference that make cellulose so strong!This structure has H bonds holding the parallel chains together
2970 chains of β glucose combine to form a MICROFIBRIL.Lots of MICROFIBRILS are held together to formFIBRES.