What are uses and significance of sulfated polygalactans in cell wall of red algae?

Explanation

### Step-by-Step Solution:

1. **Introduction to Sulfated Polygalactans**:
- Sulfated polygalactans are polysaccharides found in the cell walls of red algae. They include substances such as agar, carrageenan, and furcellaran.

2. **Sources of Sulfated Polygalactans**:
- Agar is primarily extracted from red algae species like *Gracilaria* and *Gelidium*.
- Carrageenan is derived from *Chondrus crispus*, commonly known as Irish moss.
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