Introduction
All living organisms are made up of cells. The cell is called the fundamental unit of life because it performs all vital life functions such as nutrition, respiration, growth, and reproduction.
Discovery of Cell
- Robert Hooke discovered cells in 1665.
- He observed dead cells in cork under a microscope.
Cell Theory
Proposed by Schleiden and Schwann:
- All living organisms are made up of cells.
- Cell is the basic structural and functional unit of life.
- New cells arise from pre-existing cells.
Types of Cells
1. Prokaryotic Cells
- No true nucleus.
- No membrane-bound organelles.
- Example: Bacteria.
2. Eukaryotic Cells
- True nucleus present.
- Membrane-bound organelles present.
- Example: Plant and animal cells.
Cell Structure and Functions
1. Plasma Membrane
- Outer covering of the cell.
- Controls movement of substances in and out.
- Selectively permeable.
2. Cell Wall (Plant Cells Only)
- Rigid outer layer made of cellulose.
- Provides shape and protection.
3. Nucleus
- Control center of the cell.
- Contains genetic material (DNA).
- Regulates cell activities.
4. Cytoplasm
- Jelly-like substance inside the cell.
- Site of most chemical reactions.
5. Mitochondria
- Known as the powerhouse of the cell.
- Produces energy (ATP).
6. Endoplasmic Reticulum (ER)
- Helps in transport of materials.
- Types:
- Rough ER: Protein synthesis.
- Smooth ER: Lipid synthesis.
7. Golgi Apparatus
- Modifies, packages, and transports proteins.
8. Ribosomes
- Site of protein synthesis.
- Found freely in cytoplasm or on ER.
9. Lysosomes
- Known as suicide bags.
- Digest waste materials and dead cells.
10. Vacuole
- Stores food, water, and waste.
- Large central vacuole in plant cells.
11. Plastids (Plant Cells Only)
- Chloroplast: Photosynthesis.
- Chromoplast: Color.
- Leucoplast: Storage.
Difference Between Plant and Animal Cell
| Feature | Plant Cell | Animal Cell |
|---|---|---|
| Cell wall | Present | Absent |
| Chloroplast | Present | Absent |
| Vacuole | Large | Small or absent |
| Shape | Regular | Irregular |
Quick Short Q&A (Most Possible)
| Question | Short Answer |
|---|---|
| Fundamental unit of life? | Cell |
| Who discovered the cell? | Robert Hooke |
| What is cell theory? | All organisms made of cells |
| Prokaryotic cell example? | Bacteria |
| Powerhouse of cell? | Mitochondria |
| Protein synthesis site? | Ribosomes |
| Suicide bags of cell? | Lysosomes |
| Control center of cell? | Nucleus |
| Photosynthesis occurs in? | Chloroplast |
| Selectively permeable membrane? | Plasma membrane |