🧬 Basics of Cell
🌱 1. Definition
A cell is the smallest structural and functional unit of life.
It is often called the “building block of life” because every living organism — from the simplest
bacterium to humans — is made up of one or more cells.
🧫 2. Discovery of Cell
Robert Hooke (1665):
Observed thin slices of cork under a microscope and coined the term “cell” (from Latin cellula,
meaning small room).
Anton van Leeuwenhoek (1674):
First to observe living cells (like bacteria and protozoa).
Schleiden and Schwann (1838–1839):
Proposed the Cell Theory:
All living things are made up of cells.
The cell is the basic unit of structure and function.
Rudolf Virchow (1855):
Added: “All cells arise from pre-existing cells.”
⚙️ 3. Types of Cells
Cells differ mainly based on complexity and organization:
Type Example Characteristics
Prokaryotic Cells Bacteria, Cyanobacteria No nucleus; genetic material lies free in the
cytoplasm (nucleoid); lack membrane-bound organelles
.
Eukaryotic Cells Plants, Animals, Fungi, Protists Have a true nucleus with nuclear
membrane; contain membrane-bound organelles like mitochondria, ER, Golgi, etc.
, 🧩 4. Main Parts of a Cell
Every typical eukaryotic cell has three main components:
(a) Cell Membrane (Plasma Membrane)
Thin, flexible boundary that surrounds the cell.
Made up of: Lipid bilayer with proteins (Fluid Mosaic Model).
Functions:
Controls entry and exit of substances (selectively permeable).
Helps in cell communication and recognition.
(b) Cytoplasm
Jelly-like fluid inside the cell between the membrane and nucleus.
Contains organelles (specialized structures performing specific functions).
Site of many metabolic reactions.
(c) Nucleus
🌱 1. Definition
A cell is the smallest structural and functional unit of life.
It is often called the “building block of life” because every living organism — from the simplest
bacterium to humans — is made up of one or more cells.
🧫 2. Discovery of Cell
Robert Hooke (1665):
Observed thin slices of cork under a microscope and coined the term “cell” (from Latin cellula,
meaning small room).
Anton van Leeuwenhoek (1674):
First to observe living cells (like bacteria and protozoa).
Schleiden and Schwann (1838–1839):
Proposed the Cell Theory:
All living things are made up of cells.
The cell is the basic unit of structure and function.
Rudolf Virchow (1855):
Added: “All cells arise from pre-existing cells.”
⚙️ 3. Types of Cells
Cells differ mainly based on complexity and organization:
Type Example Characteristics
Prokaryotic Cells Bacteria, Cyanobacteria No nucleus; genetic material lies free in the
cytoplasm (nucleoid); lack membrane-bound organelles
.
Eukaryotic Cells Plants, Animals, Fungi, Protists Have a true nucleus with nuclear
membrane; contain membrane-bound organelles like mitochondria, ER, Golgi, etc.
, 🧩 4. Main Parts of a Cell
Every typical eukaryotic cell has three main components:
(a) Cell Membrane (Plasma Membrane)
Thin, flexible boundary that surrounds the cell.
Made up of: Lipid bilayer with proteins (Fluid Mosaic Model).
Functions:
Controls entry and exit of substances (selectively permeable).
Helps in cell communication and recognition.
(b) Cytoplasm
Jelly-like fluid inside the cell between the membrane and nucleus.
Contains organelles (specialized structures performing specific functions).
Site of many metabolic reactions.
(c) Nucleus
