Card Set Information
How does the structure of polysaccharides help them to carry out their function?
Chains may be folded, making them compact and ideal for storage.
The size of the molecules make them insoluble, making them ideal for storage as they are osmotically inactive/do not affect water potential of the cell and do not easily diffuse out of the cell.
Starch has monomers of ___________, and its function is to ___________ formed from any excess __________.
alpha-glucose, reserve food, glucose
Starch comprises of 20% amylose, 79% amylopectin & 1% phosphates and fatty acids.
Compact shape means many glucose residues can be stored in a small volume.
By converting small flucose molecules into a polysaccharide, small molecules are stored in large macromolecules.
Less water will enter by osmosis as the cell is less concentrated.
Structure of Amylose
300 alpha-glucose units, bonded by alpha-1,4 glycosidic linkages, making a 109 degree angle between 2 C-O bonds
causing the polymer to twist into a helix.
OH group of C2 projects out into the middle and form H bonds with each other, stabilising the shape.
Structure of Amylopectin
Highly branched chains of 1300-1500 alpha-glucose subunits
alpha-1,4 glycosidic linkages give helical chains
alpha-1,6 glycosidic linkages give branch points
In starch, amylopectin and amylose fit together to form a complex 3D structure in which amylose helices entangle in the branches of amylopectin molecules.
comprises of alpha-glucose units with alpha-1,4 glycosidic linkages in helical chains and alpha-1,6 glycosidic linkages where branching occurs.
similar to amylopectin but has shorter chains and is more highly branched,
heavier, more compact and insoluble
high Mr - 10000 beta-glucose monomers
glucose molecule rotated 180 degrees, upside down relative to adj molecule, giving a beta-1,4 glycosidic bond
successive molecules linked 180 degrees to each other by beta-1,4 glycosidic bonds
which are unreactive and can only by hydrolysed by cellulase.
(-OH) groups project from both sides of chain form H bonds with each other, forming cross-links
In a cell wall, 60-70 molecules become tightly cross-linked forming bundles of microfibrils which run roughly parallel to each other
Microfibrils are held together by H bonds to form fibres
Fibres embedded in gel-like organic matrix containing hemicelluloses and pectins, which help transfer the stress to fibres, increasing resistance to compression
Where are starch, glycogen and cellulose found?
Starch granules in chlorophyll
Glycogen granules in cytoplasm of skeletal muscles and liver
Cell wall of plants