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What are the three basic structures of a cell? Explain.

GeneralClass 12AllAnswered 27 Mar 2026
Answer

All cells possess three fundamental components:

1. Plasma Membrane (Cell Membrane)

  • Structure: Phospholipid bilayer with embedded proteins (fluid mosaic model)
  • Function:
    • Forms selective barrier between cell and environment
    • Regulates transport of substances
    • Cell recognition and signaling
    • Receptors for hormones and chemical signals

2. Nucleus (or Nucleoid in Prokaryotes)

In Eukaryotes:

  • Double membrane-bound structure
  • Contains chromosomes (DNA + histone proteins)
  • Genetic control center – regulates gene expression
  • Houses nucleolus (rRNA synthesis)

In Prokaryotes:

  • Nucleoid region – no membrane
  • Circular DNA lies free in cytoplasm

3. Cytoplasm

  • Semi-fluid matrix (cytosol) occupying cell volume
  • Composition:
    • Water (70–90%)
    • Proteins, enzymes, salts, organic molecules
    • Organelles (membrane-bound and non-membrane-bound)
  • Functions:
    • Site of metabolic pathways (glycolysis, protein synthesis)
    • Provides structural support (cytoskeleton)
    • Intracellular transport

Significance: These three components define the minimal cellular organization necessary for life processes.

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