Key Features of a Cell:
All living organisms are made up of cells.
Cells contain organelles that perform specific functions.
Some organisms are single-celled (like bacteria), while others are multicellular (like humans and plants).
According to Cell Theory, all cells come from pre-existing cells.
Types of Cells
Cells are mainly of two types:
1. Prokaryotic Cells (e.g., Bacteria)
Simple and small (1-10 µm).
No nucleus (DNA floats freely in the cytoplasm).
Lack membrane-bound organelles.
2. Eukaryotic Cells (e.g., Plants, Animals, Fungi)
Complex and larger (10-100 µm).
Have a nucleus that contains DNA.
Contain membrane-bound organelles like mitochondria, Golgi apparatus, etc.
Structure of a Cell (Eukaryotic Cell)
A typical eukaryotic cell consists of:
1. Cell Membrane – Controls what enters and exits the cell.
2. Cytoplasm – Jelly-like substance where organelles are suspended.
3. Nucleus – Control center of the cell, contains DNA.
4. Organelles (perform specific functions):
Mitochondria – Produces energy (ATP).
Ribosomes – Helps in protein synthesis.
Endoplasmic Reticulum (ER) – Helps in making proteins and lipids.
Golgi Apparatus – Packages and transports proteins.
Lysosomes – Breaks down waste and harmful substances.
Vacuoles – Stores water, nutrients, and waste.
Chloroplasts (only in plant cells) – Performs photosynthesis.
Functions of a Cell
Metabolism – Converts nutrients into energy.
Growth and Repair – Divides to produce new cells.
Reproduction – Produces new organisms (unicellular) or new cells (multicellular).
Response to Stimuli – Reacts to the environment.
Conclusion
A cell is the fundamental unit of life, playing a crucial role in the survival of organisms. It can be simple (prokaryotic) or complex (eukaryotic), and each type has unique structures and functions.