Cell Theory & Cell Overview

Characteristics of Cells

  • Microscopic; visible only via microscopes.
  • High surface  area/volume\text{surface\;area}/\text{volume} ratio ensures efficient nutrient uptake & waste removal.
  • Serve as the basic structural and functional units of every organism.

Why Cells Are Small

  • Decreasing size increases SA:Vol\text{SA:Vol}, maintaining rapid exchange of materials.
  • Limits waste build-up and meets metabolic demands.

General Functions of Cells

  • Maintain internal balance (homeostasis).
  • Acquire & convert chemical energy for work.
  • Detect and respond to environmental changes.
  • Provide protection and structural support.

Key Scientists & Timeline

  • 1585−16321585{-}1632 Zacharias Janssen – built first compound microscope.
  • 1635−17031635{-}1703 Robert Hooke – observed cork, coined "cell".
  • 1626−16971626{-}1697 Francesco Redi – experiments refuted spontaneous generation.
  • 1632−17231632{-}1723 Anton van Leeuwenhoek – first to view microorganisms.
  • 1804−18811804{-}1881 Matthias Schleiden – all plants are cellular.
  • 1810−18821810{-}1882 Theodor Schwann – all animals are cellular.
  • 1821−19021821{-}1902 Rudolf Virchow – cells originate only from pre-existing cells.

Three Principles of Cell Theory

  • Every living organism is composed of one or more cells.
  • The cell is the fundamental unit of structure and function.
  • All cells arise from pre-existing cells, passing hereditary material to progeny.

Cell Theory vs. Spontaneous Generation

  • Cell theory: life comes only from existing cells (biogenesis).
  • Spontaneous generation: life emerges from non-living matter (disproved).
  • Both address life’s origin; only cell theory is scientifically accepted.

Quick Exam Prompts

  • Sterilization & disinfection apply Principle 33 (blocking microbial cell introduction).
  • New pimple formation illustrates Principle 33 (new skin cells generated).