The Fundamental Unit of Life
Cells are the basic building units of all organisms which have similar structures visible under a
microscope.
Cells were first discovered by Robert Hooke in 1665, with the help of a primitive microscope. He
observed that cork, a substance from tree bark, resembled a honeycomb structure with many
compartments. He named these boxes cells, a Latin word meaning "little room."
Leeuwenhoek discovered living cells in pond water in 1674.
Robert Brown discovered the nucleus in 1831.
Purkinje coined the term 'protoplasm' in 1839.
The cell theory, which states that all plants and animals are composed of cells and that the cell is the
basic unit of life, was presented by Schleiden and Schwann in 1838 and expanded by Virchow in
1855 by saying that all cells arise from pre-existing cells.
The discovery of the electron microscope in 1940 allowed for the observation and understanding of
the complex structure of cells and their various organelles.
Unicellular Organisms – The organisms that consist of a single cell such as Amoeba.
Multicellular Organisms – The organisms that contain various cells that perform different functions in
the organism such as plants fungi and animals
The shape of the cell may vary depending on the type of function it performs in an organism. Cells
are capable of changing their shape. For example, the white blood cells and amoeba can change
shapes on their own.
CELL MEMBRANE
The plasma membrane is the outermost covering of a cell.
It separates its contents from its external environment.
It allows certain materials to enter and exit the cell while preventing others.
The cell membrane is selectively permeable, allowing substances like carbon dioxide or oxygen to
move through diffusion.
Diffusion is the movement of a substance from a region of high concentration to a region of low
concentration. For example, CO2 accumulates in high concentrations inside a cell, while its
concentration in the external environment is low. When there is a difference in CO2 concentration
inside and outside a cell, it moves out of the cell. The same process occurs for O2 entering a cell
when its concentration inside the cell decreases. Water also follows this law, as it moves through a
selectively permeable membrane through osmosis.
Osmosis is the net diffusion of water across a selectively permeable membrane towards a higher
solute concentration.
There are three types of solutions:
Cells are the basic building units of all organisms which have similar structures visible under a
microscope.
Cells were first discovered by Robert Hooke in 1665, with the help of a primitive microscope. He
observed that cork, a substance from tree bark, resembled a honeycomb structure with many
compartments. He named these boxes cells, a Latin word meaning "little room."
Leeuwenhoek discovered living cells in pond water in 1674.
Robert Brown discovered the nucleus in 1831.
Purkinje coined the term 'protoplasm' in 1839.
The cell theory, which states that all plants and animals are composed of cells and that the cell is the
basic unit of life, was presented by Schleiden and Schwann in 1838 and expanded by Virchow in
1855 by saying that all cells arise from pre-existing cells.
The discovery of the electron microscope in 1940 allowed for the observation and understanding of
the complex structure of cells and their various organelles.
Unicellular Organisms – The organisms that consist of a single cell such as Amoeba.
Multicellular Organisms – The organisms that contain various cells that perform different functions in
the organism such as plants fungi and animals
The shape of the cell may vary depending on the type of function it performs in an organism. Cells
are capable of changing their shape. For example, the white blood cells and amoeba can change
shapes on their own.
CELL MEMBRANE
The plasma membrane is the outermost covering of a cell.
It separates its contents from its external environment.
It allows certain materials to enter and exit the cell while preventing others.
The cell membrane is selectively permeable, allowing substances like carbon dioxide or oxygen to
move through diffusion.
Diffusion is the movement of a substance from a region of high concentration to a region of low
concentration. For example, CO2 accumulates in high concentrations inside a cell, while its
concentration in the external environment is low. When there is a difference in CO2 concentration
inside and outside a cell, it moves out of the cell. The same process occurs for O2 entering a cell
when its concentration inside the cell decreases. Water also follows this law, as it moves through a
selectively permeable membrane through osmosis.
Osmosis is the net diffusion of water across a selectively permeable membrane towards a higher
solute concentration.
There are three types of solutions:
