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Explain the terms related to a prokaryotic cell: (a) Mesosomes (b) Chromatophores

GeneralClass 12AllAnswered 27 Mar 2026
Answer

(a) Mesosomes

  • Definition: Specialized invaginations (infoldings) of the prokaryotic plasma membrane extending into cytoplasm
  • Structure: Complex, convoluted membranous structures (vesicular, tubular, or lamellar)
  • Proposed functions (debated):
    1. Respiration: Increase surface area for respiratory enzymes (electron transport chain)
    2. Cell division: DNA replication attachment site; septum formation
    3. Secretion: Enzyme secretion
    4. Surface area enhancement: Compensate for lack of internal membranes

Controversy: Some researchers argue mesosomes are artifacts of chemical fixation during electron microscopy preparation.

(b) Chromatophores

  • Definition: Membranous extensions in photosynthetic prokaryotes (cyanobacteria, purple/green bacteria)
  • Structure: Vesicular or lamellar invaginations of plasma membrane
  • Content: Photosynthetic pigments:
    • Chlorophyll a (cyanobacteria)
    • Bacteriochlorophyll (photosynthetic bacteria)
    • Carotenoids (accessory pigments)
  • Function: Site of photosynthesis (analogous to chloroplast thylakoids in eukaryotes)

Types:

  • Thylakoids in cyanobacteria (similar to chloroplast thylakoids)
  • Chlorosomes in green sulfur bacteria

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