The key property distinguishing polysaccharide a (an energy storage polysaccharide in plants) from polysaccharides b and c (structural polymers in woody tissues) is their molecular structure, specifically the type of glycosidic linkages and resulting three-dimensional organization. Energy storage polysaccharide (a):
- Typically starch, which is composed of α-glycosidic linkages (α-1,4 and α-1,6 bonds).
- These linkages create a helical, branched structure that is more readily digestible and soluble, making it suitable for energy storage and mobilization in plants.
Structural polysaccharides (b and c):
- Primarily cellulose and hemicelluloses found in woody tissues.
- Cellulose consists of β-1,4-glycosidic linkages, forming long, linear, unbranched chains that aggregate into rigid, crystalline microfibrils.
- This β-linkage and linear structure result in strong hydrogen bonding between chains, providing mechanical strength and insolubility, essential for structural support in plant cell walls.
- Hemicelluloses like xylans have a more complex, branched structure and interact covalently or non-covalently with lignin and cellulose, contributing to the composite strength of woody tissues.
Thus, the critical distinguishing property is the type of glycosidic linkage (α vs. β) and the resulting molecular architecture (branched helical vs. linear crystalline). This difference influences solubility, digestibility, and mechanical strength, aligning with their functional roles as energy storage or structural support
