Overview
This lecture covers the core concepts, history, and principles of cell theory, its main tenets, and real-world applications in biology and medicine.
History of Cell Theory
- In 1665, Robert Hooke observed and named "cells" while examining cork under a microscope.
- Antonie van Leeuwenhoek was the first to observe living cells (animalcules) in pond water.
- Matthias Schleiden concluded all plants are made of cells; Theodor Schwann stated all animals are made of cells.
- Rudolf Virchow asserted that all cells arise from preexisting cells, challenging the idea of spontaneous generation.
Main Tenets of Cell Theory
- All living organisms are composed of one or more cells.
- The cell is the basic unit of structure and function in living organisms.
- All cells come from preexisting cells through cell division.
Types of Organisms and Cells
- Unicellular organisms (e.g., bacteria, amoebas) consist of a single cell that performs all life functions.
- Multicellular organisms (e.g., humans, plants) have many specialized cells working together.
Cell Structure and Function
- The cell membrane regulates entry and exit, protecting the cell.
- The nucleus contains DNA and directs cellular activities.
- The cytoplasm is a gel-like substance where cell processes occur and structures are suspended.
Cell Division
- Mitosis is the process for growth, repair, and replacement of cells, producing two identical cells.
- Meiosis produces sex cells (sperm and egg) with half the normal chromosome number for reproduction.
- These processes show that life continues through cellular reproduction, not spontaneous generation.
Applications and Implications of Cell Theory
- Understanding cell division helps in studying and treating diseases like cancer.
- Stem cell research uses cells' ability to become various cell types for treatments and growing new tissues.
- Genetic engineering modifies DNA in cells to cure genetic diseases or create genetically modified organisms (GMOs).
Key Terms & Definitions
- Cell — The smallest structural and functional unit of living organisms.
- Unicellular — Organisms made of a single cell.
- Multicellular — Organisms made of many cells.
- Cell membrane — The protective outer layer regulating substances entering or leaving the cell.
- Nucleus — Organelle containing DNA and controlling cell activities.
- Cytoplasm — Gel-like material inside the cell where all organelles are suspended.
- Mitosis — Cell division process producing two identical cells.
- Meiosis — Cell division process producing sex cells with half the chromosome number.
- Stem cells — Unspecialized cells capable of developing into different cell types.
- Spontaneous generation — Disproven idea that life arises from non-living matter.
Action Items / Next Steps
- Review cell structure diagrams and memorize the three main tenets of cell theory.
- Prepare for questions on the history and scientists involved in cell theory.
- Read the next module on cell organelles and their specific functions.