✅ 5. Other Polysaccharides Used for Building
These are not for energy but for structure and support.
🪵 1) Pectin and Lignin – Plant Builders
- Found in the cell walls of plants.
- Give support, especially in woody or ripening fruits.
- Lignin is very hard and waterproof (like in trees).
- Pectin helps hold plant cells together, especially in fruit skins.
🍎 Pectin is also used in jam-making because it forms jelly when heated with sugar.
🌊 2) Agar – From Red Algae
- Found in red algae (seaweed).
- Used in:
- Food industry as a thickener (e.g., in jellies).
- Laboratories as a medium to grow bacteria and fungi (like jelly on a petri dish).
🧫 Analogy: Agar is like the jelly platform where scientists “plant” bacteria to grow and study.
🦠 3) Murein – The Bacterial Wall Builder
- Found in the cell walls of prokaryotes (bacteria).
- It is a sugar-peptide polymer:
- Sugar part: like cellulose
- Peptide part: chains of amino acids
⚔️ Murein gives protection and shape to bacterial cells.
💊 Antibiotics like penicillin attack the murein layer — making bacteria burst.
✅ 🌟 Summary Table: Polysaccharides for Structure
| Polysaccharide | Found In | Structure Type | Role |
| Cellulose | Plants (cell wall) | Beta-glucose, straight chains | Gives strength to plant cells |
| Chitin | Insects, fungi | Modified glucose with nitrogen | Tough protection (exoskeletons) |
| Pectin & Lignin | Plants (cell wall) | Complex carbs | Support in fruits/wood |
| Agar | Red algae | Gel-like polysaccharide | Food thickener, lab medium |
| Murein | Bacteria (prokaryotes) | Sugar + peptide | Protects bacterial cells |