1. Cell – The Basic Unit of Life
The cell is the basic structural and functional unit of all living organisms.
Every living organism is made up of one or more cells.
Cells perform all life processes like nutrition, respiration, growth, and reproduction.
Cell Theory
All living organisms are made up of cells.
The cell is the basic unit of life.
New cells arise only from pre-existing cells.
Scientists to Remember
Robert Hooke (1665): Discovered cells in cork.
Anton van Leeuwenhoek: First observed living cells.
Robert Brown: Discovered the nucleus.
Schleiden & Schwann: Proposed Cell Theory.
Rudolf Virchow: "All cells arise from pre-existing cells."
2. Types of Organisms
Unicellular Organisms
Made of only one cell.
Example: Amoeba, Paramecium, Bacteria.
Multicellular Organisms
Made of many cells.
Example: Humans, Mango tree, Dog.
3. Cell Shape and Size
Cells vary in shape and size according to their function.
Nerve cell – Long and branched.
Muscle cell – Spindle-shaped.
Red blood cell – Disc-shaped.
White blood cell – Irregular.
, 4. Cell Structure
A cell has three main parts:
1. Cell membrane
2. Cytoplasm
3. Nucleus
5. Cell Membrane (Plasma Membrane)
Thin, flexible outer covering of the cell.
Protects the cell.
Gives shape.
Controls movement of substances in and out.
Selectively permeable membrane (allows only certain substances to pass).
6. Diffusion
Left: 23 O₂Right: 9 O₂
Net diffusion
Random motion carries molecules both ways, but more move from the more concentrated
side to the less concentrated side.
Initial molecules on left
27
O₂
Initial molecules on left
Learn more
Movement of molecules from higher concentration to lower concentration.
Does not require energy.
Example
Oxygen enters the cell and carbon dioxide moves out.
7. Osmosis
Isotonic outside → little net movement
coutc_{out}cout
The cell is the basic structural and functional unit of all living organisms.
Every living organism is made up of one or more cells.
Cells perform all life processes like nutrition, respiration, growth, and reproduction.
Cell Theory
All living organisms are made up of cells.
The cell is the basic unit of life.
New cells arise only from pre-existing cells.
Scientists to Remember
Robert Hooke (1665): Discovered cells in cork.
Anton van Leeuwenhoek: First observed living cells.
Robert Brown: Discovered the nucleus.
Schleiden & Schwann: Proposed Cell Theory.
Rudolf Virchow: "All cells arise from pre-existing cells."
2. Types of Organisms
Unicellular Organisms
Made of only one cell.
Example: Amoeba, Paramecium, Bacteria.
Multicellular Organisms
Made of many cells.
Example: Humans, Mango tree, Dog.
3. Cell Shape and Size
Cells vary in shape and size according to their function.
Nerve cell – Long and branched.
Muscle cell – Spindle-shaped.
Red blood cell – Disc-shaped.
White blood cell – Irregular.
, 4. Cell Structure
A cell has three main parts:
1. Cell membrane
2. Cytoplasm
3. Nucleus
5. Cell Membrane (Plasma Membrane)
Thin, flexible outer covering of the cell.
Protects the cell.
Gives shape.
Controls movement of substances in and out.
Selectively permeable membrane (allows only certain substances to pass).
6. Diffusion
Left: 23 O₂Right: 9 O₂
Net diffusion
Random motion carries molecules both ways, but more move from the more concentrated
side to the less concentrated side.
Initial molecules on left
27
O₂
Initial molecules on left
Learn more
Movement of molecules from higher concentration to lower concentration.
Does not require energy.
Example
Oxygen enters the cell and carbon dioxide moves out.
7. Osmosis
Isotonic outside → little net movement
coutc_{out}cout
