Class 8 - The Cell CBSE/ICSE Science Notes

Cell:-

➥The basic, structural and functional units of life is cell.

➥Every living organism is made up of cells.

Cell Theory

➥All living things are composed of cell.

➥Cells are the basic structual and functional units.

➥New cells are produced from exiting cells.

Discovery of Cell

➥Robert Hooke (1665): Discovered and named cells in cork.

➥Anton van Leeuwenhoek (1674): First to see living cells.

➥Matthias Schleiden (1838): Found that all plants are made of cells.

➥Theodor Schwann (1839): Found that all animals are made of cells.

➥Rudolf Virchow (1855): Stated that all cells come from existing cells.

Types of Cells

➥ Prokaryotic Cells: Do not have a nucleus. Example: Bacteria.

➥ Eukaryotic Cells: Have a nucleus. Examples: Animal and Plant cells.

Structure of a Cell

➥ A cell consists of the following parts:

1. Cell Membrane: The outer boundary of the cell that controls the entry and exit of substances.
2. Cytoplasm: Jelly-like fluid inside the cell where organelles are suspended.
3. Nucleus: The control center of the cell containing genetic material (DNA).
4. Organelles: Specialized structures within the cell, each with specific functions.

Functions of Cell Organelles

Organelle	Function
Cell Membrane	Protects and organizes the cell, controls entry and exit of substances.
Cytoplasm	Supports and suspends organelles, site of many cellular processes.
Nucleus	Controls cell activities, contains genetic material.
Mitochondria	Produces energy through respiration.
Ribosomes	Synthesizes proteins.
Endoplasmic Reticulum	Transports materials within the cell.
Golgi Apparatus	Modifies, sorts, and packages proteins and lipids.
Lysosomes	Digest and remove waste.
Chloroplasts (in Plant Cells)	Site of photosynthesis.
Vacuoles	Stores nutrients, waste products, and helps in maintaining turgor pressure.

Differences Between Plant and Animal Cells

➥ Difference between a plant cell and an animal cell:-

Feature	Plant Cells	Animal Cells
Cell Wall	Present	Absent
Chloroplasts	Present	Absent
Vacuoles	Large, central	Small, numerous
Shape	Rectangular	Round