Polysaccharides

Polysaccharides

Polysaccharides are made up of many monosaccharides joined together through condensation reactions, this results in the formation of chains which are polymers. Monosaccharides are joined together in chains with glycosidic bonds between each monosaccharide. When polysaccharides are broken down, the glycosidic bonds are broken down in hydrolysis reactions, they are usually broken down into disaccharides first, then monosaccharides.

Sugars are small, soluble and reactive however polymers are large, insoluble, unreactive molecules and for this reason they play a key role in storage. They won't dissolve or move around and their insolublity means they won't affect the osmotic balance of cells. Polymers also have roles in structural support.

Starch

• A polymer of alpha (α) glucose molecules joined by 1,4 glycosidic bonds
• It's stored in plants as a future energy source, in the plant cells as amyloplasts
• Amyloplasts are made up of 2 compounds: amylose and amylopectin. The amount of these two compounds can vary, this makes starches that digest faster and starches that digest slower.
• Amylose is a linear (unbranched) polymer which coils into a helix and forms the outside of the amyloplast. It has only one end in which enzymes can attach to, therefore it takes a long time for the enzyme to break it down.
• Amylopectin is a branched polymer which forms the core of the amyloplast, this has many ends in whcih enzymes can attach to, it is broken down much quicker than amylose. However, plants barely reach the…