Q.17 Which of the following is not associated with the extracellular matrix of the cells?
- Proteoglycans
- Cellulose
- Collagen
- Fibronectin
Cellulose is not associated with the extracellular matrix (ECM) of animal cells, as it is a plant-specific cell wall polysaccharide absent in animal tissues.
Question Analysis
This question evaluates knowledge of ECM composition in animal cells, which provides structural support, signaling, and hydration via proteins and glycoproteins.
Option Breakdown
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Proteoglycans: Core proteins with glycosaminoglycan chains forming hydrated gels; bind water, growth factors, and contribute to ECM resilience (e.g., aggrecan in cartilage).
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Cellulose: β-1,4-glucose polymer forming rigid microfibrils in plant cell walls; animals lack cellulose synthase, so it’s irrelevant to animal ECM.
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Collagen: Most abundant ECM protein (28 types); triple-helix fibrils provide tensile strength (e.g., type I in tendons).
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Fibronectin: Dimeric glycoprotein linking ECM to integrins on cells; organizes collagen assembly and mediates adhesion/migration.
Answer: Cellulose—plant-specific, not in animal ECM.
Introduction to ECM Structure
The not associated with extracellular matrix of cells is cellulose, a plant polymer absent in animal tissues. Animal ECM relies on proteins like collagen for support and signaling.
Key ECM Components
Proteoglycans hydrate tissues; collagen forms scaffolds; fibronectin enables cell adhesion. These interact via integrins for tissue integrity and repair.
Option Found in Animal ECM? Role Proteoglycans Yes Hydration, growth factor binding Cellulose No Plant cell wall rigidity Collagen Yes Structural framework Fibronectin Yes Cell-ECM adhesion Why Cellulose Excluded
Animal ECM evolved fibrous proteins over plant-like polysaccharides; cellulose synthase genes are plant-specific. Crucial distinction for cell biology exams.
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