Overview
This lecture covers the historical discovery of the cell, the development of cell theory, and essential features common to all cells.
Discovery of the Cell
- The compound microscope was invented by Dutch spectacle maker Zacharias Janssen in 1608.
- Antonie van Leeuwenhoek developed a powerful microscope (200-300x magnification) using glass pearls and observed living microbes.
- Robert Hooke created a compound microscope (40-50x magnification) and published "Micrographia" with detailed drawings.
- Hooke observed cork and named the honeycomb-like structures "cells."
- Leeuwenhoek observed microorganisms in pond water, red blood cells, and bacteria (living "animalcules") and reported findings to the Royal Society.
Development of Cell Theory
- Matthias Schleiden (1838) concluded that all plants are made up of cells.
- Theodor Schwann (1839) concluded that all animals are made of cells.
- Rudolf Virchow (1855) observed cell division and proposed that cells arise from pre-existing cells.
- The three main points of cell theory:
- All organisms are composed of one or more cells.
- The cell is the smallest working unit of life.
- All cells arise from pre-existing cells.
Advances in Microscopy
- In 1931, Max Knoll and Ernst Ruska invented the electron microscope, allowing visualization of subcellular structures.
Fundamental Features of All Cells
- All cells possess a plasma membrane (cell membrane), cytoplasm, ribosomes, and DNA.
Key Terms & Definitions
- Cell — The basic structural and functional unit of life.
- Microscope — An instrument used to magnify small objects.
- Electron Microscope — A microscope that uses electrons for higher-resolution imaging.
- Cell Theory — The scientific theory stating all living things are made of cells, cells are basic units, and cells come from other cells.
- Plasma Membrane — The boundary that encloses a cell.
- Cytoplasm — The fluid substance within a cell.
- Ribosomes — Structures that synthesize proteins.
- DNA — The molecule carrying genetic information.
Action Items / Next Steps
- Review the main events and scientists in the discovery of the cell and cell theory.
- Memorize the three points of the cell theory and four common features of all cells.