*3.1. Polysaccharides*

Seaweeds have a significant carbohydrate component in their cell membranes, or these polysaccharides are unique to every variety from algae: Brown alginate contains fucoidan; green Ulvan or red agar contains carrageenan. Polysaccharides are becoming increasingly popular as a result of their physicochemical properties [27]. Polysaccharides are biopolymers created from natural resources that have developed as a sustainable and environmentally friendly alternative to typical polymers and plastics. They are also known as an energy store and structural molecules in a variety of species, including plants and marine organisms. Polysaccharides are the major macromolecule in seaweed, accounting for more than 80% of its weight. Polysaccharides are classified into two types based on where they are found in seaweeds: cell-membrane polysaccharides or storage polysaccharides. With the exception of accumulating carbohydrates found in cell plastids, the majority of seaweed polysaccharides are cell-membrane polysaccharides. At present, they can be classed as food-grade or non-food-grade polysaccharides, depending on how they are used [28].
