The vegetative cell has a cellulosic wall usually covered on the outside by a gelatinous coating of algin. On the cell wall of brown algae, some colloid substances like fucinic acid, alginic acid and fucoidan are present which are known as hydrocolloids. The cell wall of red algae is complex and made up of cellulose & pectin. The cell wall of red algae is also complicated like blue-green algae. Their cell wall has many different types of substances such as xylan, galactose, polyuronic acid, polysulfate esters. In dinoflagellates, cell wall has a stiff cellulose plate on the outer surface.
In diatoms, the cell wall is made up of silica (hydrated silicon dioxide) called as frustule. They are the major group of algae, most common Chrysophytes.

Polyuronic acid and polysulphate esters in the cell wall of Red Algae:

Polyuronic acid and polysulphate esters are characteristic components found in the cell wall of Red Algae. These components play important roles in maintaining the structural integrity and functionality of the cell wall.

Cell wall composition of Red Algae:

The cell wall of Red Algae is composed of various polysaccharides, including cellulose, agar, carrageenan, and other sulfated polysaccharides. Among these, polyuronic acid and polysulphate esters are major components that confer unique properties to the cell wall.

Polyuronic acid:

Polyuronic acid is a polysaccharide composed of repeating units of uronic acid, such as glucuronic acid or iduronic acid. It is highly negatively charged due to the presence of carboxyl groups in the uronic acid residues. This negative charge contributes to the overall charge of the cell wall and enables the absorption of ions and water.

Polyuronic acid is involved in various physiological processes, including cell adhesion, protection against desiccation, and defense against pathogens. It forms a gel-like matrix within the cell wall, providing mechanical strength and resistance to environmental stresses.

Polysulphate esters:

Polysulphate esters are ester derivatives of polysaccharides that contain sulfate groups. In the cell wall of Red Algae, these polysulphate esters are commonly found in sulfated polysaccharides such as carrageenan and agar. The sulfate groups in these polysaccharides contribute to their unique properties, including gel-forming abilities, water-holding capacity, and resistance to microbial degradation.

Polysulphate esters play essential roles in the cell wall, such as maintaining cell shape, preventing water loss, and providing protection against pathogens and herbivores. They also contribute to the rheological properties of the cell wall, influencing the viscosity and texture of the algal extract.

Functions of polyuronic acid and polysulphate esters in the cell wall:

1. Structural integrity: Polyuronic acid and polysulphate esters contribute to the strength and rigidity of the cell wall, providing support and protection to the algal cells.

2. Water retention: These components have hydrophilic properties that enable the cell wall to retain water, preventing desiccation and maintaining turgidity.

3. Ion absorption: The negative charge of polyuronic acid and sulfate groups in polysulphate esters allows the cell wall to absorb and retain ions, which are essential for various physiological processes.

4. Defense against pathogens: Polyuronic acid and polysulphate esters can interact with pathogens, inhibiting their growth and protecting the algal cells from infection.

5. Environmental adaptation: The unique properties of polyuronic acid and polysulphate esters help Red Algae adapt to a wide range of environmental conditions, including high salinity, fluctuating water levels, and exposure to UV radiation.

In conclusion, polyuronic acid and polysulphate esters are characteristic components of the cell wall of Red Algae. These components contribute to the structural integrity, water-retaining capacity, and defense mechanisms of the cell wall, enabling Red Algae to thrive in diverse habitats.