Cytology
“Cytology is the branch of biology that studies the structure, function, and life processes of cells — the fundamental units of life.”
What is Cytology?
Cytology, also known as cell biology, deals with the study of cells, their organelles, structures, and functions. All living organisms are made up of cells — some are unicellular, while others are multicellular.
Discovery of Cell
The cell was discovered by Robert Hooke in 1665 while observing a thin slice of cork under a primitive microscope. He coined the term “cell.” Later, Anton van Leeuwenhoek observed living cells.
Types of Cells
- Prokaryotic Cells: Simple cells without a defined nucleus (e.g., bacteria).
- Eukaryotic Cells: Complex cells with a well-defined nucleus (e.g., plant and animal cells).
Cell Organelles and Their Functions
- Nucleus: Controls cellular activities and contains DNA.
- Plasma Membrane: Regulates the entry and exit of substances.
- Cytoplasm: Jelly-like substance where organelles are suspended.
- Mitochondria: Powerhouse of the cell; site of energy production.
- Endoplasmic Reticulum (ER): Involved in synthesis and transport (Rough ER and Smooth ER).
- Golgi Apparatus: Modifies, packages, and transports proteins.
- Lysosomes: Contain digestive enzymes; remove waste.
- Chloroplasts: Found only in plant cells; site of photosynthesis.
- Vacuoles: Store nutrients, waste products, and provide structural support (large in plant cells).
Cell Theory
Proposed by Schleiden and Schwann, the cell theory states:
- All living organisms are made up of cells.
- The cell is the basic structural and functional unit of life.
- All cells arise from pre-existing cells (added by Rudolf Virchow).
Differences Between Plant and Animal Cells
| Feature |
Plant Cell |
Animal Cell |
| Cell Wall |
Present |
Absent |
| Chloroplast |
Present |
Absent |
| Vacuole |
Large central vacuole |
Small or absent |
| Shape |
Fixed (rectangular) |
Irregular (round) |
Fun Fact: The human body is made up of approximately 37.2 trillion cells!
Conclusion
Cytology plays a vital role in understanding the structure and function of cells — the building blocks of life. It forms the foundation of genetics, molecular biology, and biotechnology, and is essential for comprehending the biological functions of organisms.