Cell and cell components
1. Definition of a Cell
The Cell: It is the smallest unit of our body and the basic functional and structural unit of life.
Cytology: This is the scientific study of cells.
Discovery: The cell was first discovered by Robert Hooke in 1665.
2. Shape and Size of Cells
Cells vary significantly in their physical appearance depending on the organism:
Animal Cells: Generally irregular in shape. They can also be oval, spherical, rod-like, elongated,
cubical, or columnar.
Plant Cells: Typically have a hexagonal shape.
Bacterial Cells: Can be spherical, rod-like, filamentous, or spiral.
3. Extremes in Cell Size
Biggest Cell: The egg laid by an ostrich (measuring approximately 15–18 cm in diameter).
Smallest Cell: Mycoplasma (a type of bacteria), measuring about 0.2 microns.
4. Parts of a Cell (Coverings)
The notes begin to categorize the different parts of a cell, focusing first on the outer layers:
Cell Type Outermost Layer
Animal Cell. - Cell Membrane
Plant Cells - Cell Wall
Cell Wall
The bacterial cell wall is made up of polysaccharides and amino acids.
1. The cell wall in general is made of cellulose.
2. It is hard, rigid, non-flexible, and provides a fixed shape.
3. It protects the cell from fungi, viruses, and bacteria and helps to absorb soluble
minerals from the soil and water.
Cell Membrane
1. The cell membrane is flexible, thin, and elastic.
2. It controls and coordinates intercellular transportation of fluids and is
semi-permeable as it is living in nature.
3. In unicellular protozoans like amoeba, the cell membrane helps in making
pseudopodia for capturing food, locomotion, excreting metabolic wastes, and
protecting the body from the external environment.
4. The cell membrane is composed of lipid and protein.
, Cytoplasm
Cytoplasm is a viscous, sticky, and clear semi-liquid fluid present between the cell
membrane and nucleus in a living cell.
Its functions include :
1. accomplishing metabolic activities of life processes,
2. helping to balance the amount of water and minerals in body organs,
3. containing cell components like mitochondria, Golgi body, plastids, egg
(iii) Cell components :- Various functional sites inside a cell are called cell components.
Cell components two types (Cell organelles and cell inclusion)
Cell organelles- living components of cell
cell inclusion - Non-living components of Cell
(I) Mitochondria
1. Cylindrical or filamentous in shape,
2. Bounded with double membrane,
3. The energy generated by mitochondria is used by other cell organelles to carry
out cell activities,
4. It is also called the power house of cells.
Functions of Mitochondria :
1. Stores energy in the form of ATP(Adenosine Triphosphate) before distributing it
to the cell organelles
2. Contains DNA molecules which help to transfer hereditary Characteristics from
parents to off spring
ii) Plastid :- Colourful organelles found
Found in only plant cell., some bacterial cells and in some protozoans.
1. Definition of a Cell
The Cell: It is the smallest unit of our body and the basic functional and structural unit of life.
Cytology: This is the scientific study of cells.
Discovery: The cell was first discovered by Robert Hooke in 1665.
2. Shape and Size of Cells
Cells vary significantly in their physical appearance depending on the organism:
Animal Cells: Generally irregular in shape. They can also be oval, spherical, rod-like, elongated,
cubical, or columnar.
Plant Cells: Typically have a hexagonal shape.
Bacterial Cells: Can be spherical, rod-like, filamentous, or spiral.
3. Extremes in Cell Size
Biggest Cell: The egg laid by an ostrich (measuring approximately 15–18 cm in diameter).
Smallest Cell: Mycoplasma (a type of bacteria), measuring about 0.2 microns.
4. Parts of a Cell (Coverings)
The notes begin to categorize the different parts of a cell, focusing first on the outer layers:
Cell Type Outermost Layer
Animal Cell. - Cell Membrane
Plant Cells - Cell Wall
Cell Wall
The bacterial cell wall is made up of polysaccharides and amino acids.
1. The cell wall in general is made of cellulose.
2. It is hard, rigid, non-flexible, and provides a fixed shape.
3. It protects the cell from fungi, viruses, and bacteria and helps to absorb soluble
minerals from the soil and water.
Cell Membrane
1. The cell membrane is flexible, thin, and elastic.
2. It controls and coordinates intercellular transportation of fluids and is
semi-permeable as it is living in nature.
3. In unicellular protozoans like amoeba, the cell membrane helps in making
pseudopodia for capturing food, locomotion, excreting metabolic wastes, and
protecting the body from the external environment.
4. The cell membrane is composed of lipid and protein.
, Cytoplasm
Cytoplasm is a viscous, sticky, and clear semi-liquid fluid present between the cell
membrane and nucleus in a living cell.
Its functions include :
1. accomplishing metabolic activities of life processes,
2. helping to balance the amount of water and minerals in body organs,
3. containing cell components like mitochondria, Golgi body, plastids, egg
(iii) Cell components :- Various functional sites inside a cell are called cell components.
Cell components two types (Cell organelles and cell inclusion)
Cell organelles- living components of cell
cell inclusion - Non-living components of Cell
(I) Mitochondria
1. Cylindrical or filamentous in shape,
2. Bounded with double membrane,
3. The energy generated by mitochondria is used by other cell organelles to carry
out cell activities,
4. It is also called the power house of cells.
Functions of Mitochondria :
1. Stores energy in the form of ATP(Adenosine Triphosphate) before distributing it
to the cell organelles
2. Contains DNA molecules which help to transfer hereditary Characteristics from
parents to off spring
ii) Plastid :- Colourful organelles found
Found in only plant cell., some bacterial cells and in some protozoans.
