Carbohydrates: Polysaccharides | A-level Biology | OCR, AQA, Edexcel

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The key points covered in this video include:

1. Introduction to Polysaccharides
2. Energy Stores

Introduction to Polysaccharides

The most complex carbohydrates are polysaccharides. Polysaccharides are carbohydrate polymers made up of many monosaccharides. True polysaccharides have more than 10 monosaccharides joined together - smaller chains are called oligosaccharides. Polysaccharides are formed by joining together monosaccharides in a series of condensation reactions. Polysaccharides are broken down in a series of hydrolysis reactions to form monosaccharides - this can happen in two ways: Unlike monosaccharides and disaccharides, polysaccharides are not sweet-tasting nor easily soluble - they are not sugars. A huge variety of polysaccharides can be formed by: Changing the type of monosaccharide, Changing how the monosaccharides are bonded together.

Polysaccharides as Energy Stores

α-glucose is the main source of energy in respiration. Excess chemical energy is stored in cells by forming polysaccharides of α-glucose. α-glucose polysaccharides are well-suited to energy storage for a number of reasons:They are compact so a lot of energy can be stored in a small space, They are insoluble in water so do not impact the water potential of a cell, They are large so they do not diffuse out of the cell, They can be easily hydrolysed to α-glucose when energy is needed. The properties of polysaccharides that make it suitable for energy storage are summed up as follows:

Видео Carbohydrates: Polysaccharides | A-level Biology | OCR, AQA, Edexcel канала SnapRevise