Definition of cells with their types for children
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Cell, in biology, the basic membrane-bound unit that contains the fundamental molecules of life and of which all living things are composed.
The cell is the basic unit of life. Some organisms are made up of a single cell, like bacteria, while others are made up of trillions of cells. Human beings are made up of cells, too.
Different Types of Cells
There are lots of different types of cells. Each type of cell is different and performs a different function. In the human body, we have nerve cells which can be as long as from our feet to our spinal cord. Nerve cells help to transport messages around the body. We also have billions of tiny little brain cells which help us think and muscle cells which help us move around. There are many more cells in our body that help us to function and stay alive.
Although there are lots of different kinds of cells, they are often divided into two main categories: prokaryotic and eukaryotic.
Prokaryotic Cells - The prokaryotic cell is a simple, small cell with no nucleus. Organisms made from prokaryotic cells are very small, such as bacteria. There are three main regions of the prokaryotic cell:
1) The outside protection or "envelope" of the cell. This is made up of the cell wall, membrane, and capsule.
2) The flagella, which are a whip-like appendages that can help the cell to move. Note: not all prokaryotic cells have flagella.
3) The inside of the cell called the cytoplasmic region. This region includes the nucleoid, cytoplasm, and ribosomes.
Eukaryotic Cells - These cells are typically a lot bigger and more complex than prokaryotic cells. They have a defined cell nucleus which houses the cell's DNA. These are the types of cells we find in plants and animals.