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'With reference to their chemical structures and properties, describe why starch, glycogen and cellulose are efficient storage or structural compounds.'

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Introduction

'With reference to their chemical structures and properties, describe why starch, glycogen and cellulose are efficient storage or structural compounds.' Starch is a complex carbohydrate, it's a mixture of amylose and amylopectin both of which are polysaccharides containing ?-glucose molecules linked via a condensation reaction. Amylose is a long, straight chain of ?-glucose molecules, these are linked together by a 1,4 glycosidic bond, where 1 & 4 are carbon reducing centres. + +... ?-glucose molecule ?-glucose molecule = + H20 amylose These chains of ?-glucose coil to form spirals and these are held in place by hydrogen bonds. Amylopectin, on the other hand, is a branched chain due to some of its glucose residues joining via a 1,6 glycosidic bond, however this is still formed by a condensation reaction. Due to starch being made up from amylose and amylopectin which are both polysaccharides and produced by a condensation reaction, starch can easily be broken down when H20 is added and the -o- glycosidic bond is broken, this process is called hydrolysis. ...read more.

Middle

* It doesn't take up large amounts of space. * It doesn't affect water movement across membranes and so doesn't affect other processes within a plant! Glycogen is also a complex carbohydrate and is the main storage of glucose in humans, it can be found in liver and muscle tissue. This polysaccharide is similar to that of amylopectin (found in starch) however it's even more branched, it's similar as it too is caused by a condensation reaction and so is easily breakable by hydrolysis. The adding of H20 brings about the breaking of the -o- glycosidic bond and the production of ?-glucose molecules which can then be used by the human body if needed when performing strenuous exercise. The fact that glycogen can easily be broken down is why it's an efficient storage compound in humans; it allows glucose to be readily available. Cellulose is also a complex polysaccharide consisting of over 3000 or more �-glucose molecules. ...read more.

Conclusion

Cellulose is formed when many �-glucose monomers bond together, this is a condensation reaction i.e. when bonds are made and H20 is produced. However due to the positioning of the hydroxyl group (alcohol) on each glucose monomer the pattern in cellulose is that of the glucose unit being 'flipped over' when compared to the glucose prior to itself in order for the OH groups to be in the correct position for a 1,4 glycosidic bond to form. This in turn allows two hydrogen atoms to be side by side and as a result a strong hydrogen bond is formed, adding to the structure of cellulose. + +... �-glucose �-glucose = + H20 Cellulose Cellulose is an efficient structural compound due to; * It being insoluble, so will stay rigid even when wet. * It's very strong so can withstand opposing forces. Overall starch, glycogen and cellulose are efficient at their jobs, whether it's storage or structural, for several reasons all of which have hopefully been successfully highlighted throughout this essay. Rachel Wilson 12DJ Biology Oct 2002 ...read more.

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