Prokaryotic v Eukaryotic Cells (Cambridge International AS Biology)

Structural Features of Typical Prokaryotic Cells

Spec point — "outline key structural features of a prokaryotic cell as found in a typical bacterium, including: • unicellular • generally – μm diameter • peptidoglycan cell walls • circular DNA • S ribosomes • absence of organelles surrounded by double membranes"

Structural features of typical prokaryotic cells

• Animal and plant cells are eukaryotic cells, whereas bacterial cells are prokaryotic

• Prokaryotes have a cellular structure that is distinct from eukaryotes:

  • Their genetic material is free in the cytoplasm and is circular

    • Eukaryotic genetic material is packaged as linear chromosomes in the nucleus

  • Prokaryotes lack membrane-bound organelles

    • This means that they do not have any internal structures surrounded by membrane, e.g. a nucleus or mitochondria

  • They are many times smaller than eukaryotic cells

    • Prokaryotic cells are usually 1-5 μm in diameter, while eukaryotic plant cells can be 10-100 μm across

  • Their ribosomes are structurally smaller (70 S) in comparison to those found in eukaryotic cells (80 S)

  • Their cell walls are made of peptidoglycan rather than cellulose or chitin

• Prokaryotes are always unicellular, while eukaryotic animal and plant cells can function together in multicellular organisms

Prokaryotic cells have no internal membrane-bound structures, and are smaller than eukaryotic cells

Prokaryotic v Eukaryotic Cell Structures

Spec point — 1.2.6 · compare the structure of a prokaryotic cell as found in a typical bacterium with the structures of typical eukaryotic cells in plants and animals