THE CELL; STRUCTURE, FUNCTIONS AND COMPONENTS, INCLUDING MEMBRANES, CYTOPLASM, NUCLEUS, MITOCHONDRIA, RIBOSOMES AND LYSOSOMES

Cells are the structural and functional units of life.
The tiniest living organisms are composed of only a single cell while the largest are made up of billions of cells.

Cell was discovered by the great English philosopher known as Robert Hooke in the year 1665.

When viewed under light microscopes, all cells are comprised of the following components:

1. Cell membrane: This is known as the membrane covering the cell. It is mostly called a semi-
permeable membrane that allows some substances to enter into the cell; and prevent some other substances from passing in and out of the cell. It separates the interior of the cell from the environment. Osmosis and diffusion takes place through the cell membrane.

2. Cytoplasm: The cell without it is felly like transparent
and consists of 90% of water.
Most cellular reaction take place there. It also comprises of cytosol, organelles and granules and other particles.

3. Nucleus: This is the structure that encloses the identity of the cell. It is found in eukaryotic cell. It is spherical in shape in the cell, and it controls all the activities of the cell.
It brings life to all the cells cells, and contains Chromosomes which carry the the herediatry material known as gene. It is the processing Centre of the cell.

4. Mitochondria: It is the rod-like structure in the
cytoplasm which produces energy for the cell in the form of adenosine triphosphate, ATP. It is OFTEN called POWER HOUSE of the cell because energy is derived from it.

5. Endoplasmic Reticulum: Endoplasmic reticulum is a system of channel
which connect to the nucleus and cell membranes. There are two types of endoplasmic reticulum: the rough endoplasmic and the smooth endoplasmic reticulum.

6. Vacuole: It is an enclosure – a closed say ‘within the cytoplasm in plant cells. It is large and contains cell sap. It has no definite shape or size. It contains enzymes, biological molecules, etc.

7. Ribosomes: They are granules formed freely in the
cytoplasm where they synthesize proteins. Often referred to as a complex molecular machine, they are protein builders made up of ribosomal RNA molecules.

8. Lysosomes: They are tiny spherical bodies enclosed in a single membrane and contains digestive enzymes. The purpose of these lysosomal enzymes enzymes is to digest and destroy foreign bodies. This helps to protect the cell.

9. Cell Wall: This encloses the cell membrane in a plant cell. It is made up of polysaccharides.
It is usually made up of Cellulose to support the plants. It can appear rigid or tough that is semi permeable in some cell plants.

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