Prokaryotic and Eukaryotic cells

• Prokaryotic cells


  Cells that lack a membrane-bound nucleus and membrane-bound organelles
• Eukaryotic cells


  Cells that have a membrane-bound nucleus and membrane-bound organelles
• Animal and plant cells are types of eukaryotic cells, whereas bacteria are a type of prokaryote
• Prokaryotic cells


  • Much smaller than eukaryotic cells (between 100-1000 times smaller)
  • Lack membrane-bound organelles
  • Have ribosomes that are structurally smaller (70 S) compared to eukaryotic cells (80 S)
  • Lack a nucleus, instead have a single circular DNA molecule free in the cytoplasm
  • Have a cell wall that contains murein (a glycoprotein)
• Additional structures that differentiate prokaryotic cells

  • Plasmids
  • Capsules
  • Flagellum
• Plasmids


  Small loops of DNA that are separate from the main circular DNA molecule, containing genes that can be passed between prokaryotes (e.g. genes for antibiotic resistance)
• Capsule


  An outer layer that helps protect bacteria from drying out and from attack by cells of the immune system
• Flagellum


  A long, tail-like structure that rotates, enabling the prokaryote to move (a bit like a propeller)
• Differences between prokaryotic and eukaryotic cells

  • Size
  • Genome
  • Cell division
  • Ribosomes
  • Organelles
  • Cell wall
• Prokaryotic cells


  • Smaller size (0.5-5 micrometers)
  • Circular DNA with no proteins in the cytoplasm
  • Cell division by binary fission without spindle
  • 70S ribosomes
  • Very few organelles, no membrane-bound organelles
  • Cell wall made of peptidoglycan (polysaccharide and amino acids) and murein
• Eukaryotic cells


  • Larger size (up to 100 micrometers)
  • DNA associated with histones (proteins) formed into chromosomes
  • Cell division by mitosis or meiosis with spindle
  • 80S ribosomes
  • Numerous membrane-bound organelles (single membrane: lysosomes, Golgi complex, vacuoles; double membrane: nucleus, mitochondria, chloroplast; no membrane: ribosomes, centrioles, microtubules)
  • Cell wall made of cellulose or lignin in plants, chitin in fungi