THE CONCEPT OF CELL
Cell is the smallest, basic unit of life that is responsible for all life’s process.THE SHORT HISTORY ABOUT DISCOVERY OF A CELL
The cell was first named and discovered by an English biologist called Robert Hooke in 1665. Hooke designed his own compound light microscope to observe structures which too small to be seen with the naked eye.Hooke described the cork as being made of hundreds of little boxes or small chambers surrounded by walls, giving it the appearance of a honeycomb.
He called these little boxes or chambers cells meaning “little rooms” because they resembled the small rooms monks lived in, at a monastery, called "cella" in Latin.
Since then, it has been revealed that all living things are made up of one or more cells
which save as fundamental units of life.
For example; Organisms that consist of a single cell are called Unicellular organisms and Organisms that consist of many cells are called Multicellular organisms.
The remarkable observations and conclusions made by Hooke, along with other scientists, paved the way for the development of the cell theory.
CELL THEORY
The following are the components of the cell theory:All living things are composed of one or more cells.
Cells are the basic unit of structure and functions of living things.
All new cells are produced from other cells through cell division.
Cells contain inheritable information (DNA) which controls their activities.
All cells have similar basic chemical composition.
All life processes take place in the cell.
Scientists can use the concept of the cell theory to learn about nutrition, growth, reproduction, respiration, movement, sensitivity and excretion.
TYPES OF CELLS
There are two main types of cells, namely:Prokaryotic cells.
Eukaryotic cells.
PROKARYOTIC CELLS
Prokaryotic cell is the type of cell in which nuclear materials are not bound with membrane. The cell is found in organisms called prokaryotes. Example: Bacteria and blue-green bacteria. Prokaryotes are single-celled organisms.Prokaryotic organisms are organisms which contain prokaryotic cells.
Characteristics of prokaryotic cells.
They have no true nuclei as the lack membrane bound nucleus.
They lack membrane-bound organelles such as mitochondria
They are smaller in size than eukaryotic cells.
Some of them they have flagellum for movement.
They have circular deoxyribonucleic acid (DNA).
The reproduce by binary fission and sometimes by conjugation.
They have few cell organelles.
They have different shapes like rod shape, spiral shaped, spherical shaped, comma shaped and spiralchaete shape