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Prokaryotic Cells - Cell Envelope and Its Modifications

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Estimated time: 3 minutes
CBSE: Class 12

Key Points: Cell Envelope and Its Modifications

  • The prokaryotic cell envelope has three layers: glycocalyx (outermost; slime layer or capsule), cell wall (shape and support) and plasma membrane (selectively permeable).
  • Gram-positive bacteria have a thick peptidoglycan layer, no outer membrane and appear purple. Gram-negative bacteria have a thin peptidoglycan layer, an outer membrane with lipopolysaccharides, appear pink/red and are more antibiotic-resistant.
  • Mesosomes are plasma membrane infoldings that assist in cell wall formation, DNA replication, respiration and secretion.
  • Flagella (filament + hook + basal body) help in motility. Pili and fimbriae help bacteria attach to surfaces but do not contribute to motility.
  • Chromatophores contain pigments and are found in prokaryotes like cyanobacteria.

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