Compartmentalization and Cell Size - Quick Notes

Size, range, and why cells are small

• Eukaryotic cells: ext{size} \lesssim 1\ \,\text{mm}
• Prokaryotic cells (bacteria/archaea): \sim 1\ \mu\text{m}
• Atoms: \sim 1\ \text{nm}
• Viruses sit near the edge of what we call life (size in this range)
• Why small?
  • Surface area to volume (SA:V) increases as size decreases, enabling more transport and reactions across the membrane
  • If a cell is divided into parts, the total surface area increases while the volume remains the same, boosting exchange and reactions
  • Analogy: smaller pieces of wood burn more quickly due to increased surface area for reactions
• Why not infinitely small?
  • A cell must contain hereditary material and machinery; too small to fit these components
• Two size strategies in life
  • Prokaryotes: very small
  • Eukaryotes: larger by compartmentalization (internal parts)