BIOLOGICAL MOLECULES: Polysaccharides

Polysaccharides are polymers of monosaccharides. Examples of polysaccharides, which are commonly used as energy stores, are:

-> starch in chloroplasts used as a plant energy store.

-> glycogen in the cells of muscles used as a human energy store.

Amylose consists of multiple a-glucose molecule in a chain. It has glycosidic bonds between carbon 1 and 4. This coils the molecule into a spiral shape held together with hydrogen bonds. The hyroxyl group on carbon 2 are inside the coil allowing hydrogen monds to maintain the structure and makes it less soluble.

Glycosidic bondsa re formed between carbon 1 and 4 making a long chain of glucose molecules. It also has brances of glycosidic bonds between carbon 1 and 6. Because of these glycosidic bonds, amylopectin coils into a spiral shape with branches coming off. It is found in plants.

Glyocgen is essentially the same as amylopectin, but found in animals. Glycogen again has glycosidic bonds between carbon 1 and 4 creating a long chain. It also has glycosidic bonds between carbon 1 and 6 making it highly branch. What makes glycogen different is thr 1-4 bonded chains are smaller than in amylopectin, meaning glycogen is a lot more tightly compact because of this and because of the branches and there's a less of a tendency to coil.

Cellolse are produced through b-glucose molecules bonded through condensation reactions. They're tough, insoluble and fibrous. The chains are straight and lay side by side as beta-pleated sheets. The hydrogen and hydroxyl groups on carbon 1 are inverted in beta-glucose molecules as opposed to a-glucose molecules thus meaning beta molecules are inverted 180 degrees to eachother. Hydrogen bonds gives strength and prevent spiralling. 

Microfibrils are 60-70 cellulose chains together whereas macrofibrils are 400+ microfibrils together.

Macrofibrils make up the cell wall of a plant (as plant cell walsl are made of cellulose). They run in all direction and criss cross for extra strength. There are spaces between the macrofibrils for water, so the cellulose cell wall is permeable. However, they can be made waterproof by adding waxes e.g. cutin to the macrofibrils.

Plant cell walls are made up of macrofibrils which run in all directions and criss cross for extra strength. There is also strength due to the glycosidic bonds found in the cellulose with make up microfibrils. It is difficult to digest cellulose as it is hard to break these glycosidic bonds. The cellulose also helps the structure of the plant as plants don't have a skeleton so cellulose helps give them structure and shape.The cell wall is permeable as there are spaces between macrofibrils for water. However, the macrofibrils can be made water proof by adding waxes e.g. cutin. High tensile strength prevgents it from bursting when rigid.