Subject - General Science
Chapter : Cell

Cell

Cells are small compart-ments that hold all of the biolo-gical equipments necessary to keep organisms. Cells carry out all the basic functions of life: growth, metabolism and reproduction.

Cell Theory

The term cell was coined by Robert Hooke in 1665. In 1838 matthias schleiden, German botanist proposed the idea that all plants consists of cells. In 1839, The Eodor Schwann a German zoologist asserted that all plant and animals are made up of cells. This finding forms the basis of cell theory.

Components of Cell

• In the living organisms there are two types of cellular organizations.

• If we look at very simple organisms like bacteria and blue-green algae, We will discover cells that have no defined nucleus, these are prokaryotes cells.

• The cells which have definite nucleus are known as eukaryote.

Cell membranes :

It is like a plastic bag with some tiny holes that bag holds all of the cell pieces and fluids inside the cell and keeps foreign particles outside the cell. The holes are there to let some things move in and out of the cell. Compounds called proteins and phospholipids make up most of the cell membranes the phospholipids make the basic bag.

Cytoplasm :

It is the fluid that fills a cell. Scientists used to call the fluid proto plasm.cytoplasm contain many specialized cell called organ cells. Each of these organ cells performs a specific function for the cell.

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Cell organells :

Organells are living part of the cell have definite shape, structure and functions. To keep their function different from each other these organelles use membranes bound little structure with in them selves. Some of the important organells are :

• Endoplasmic reticulum : It is a network of tulsular membranes connected at one end to the nucleus and on the other to the plasma membranes.

• Ribosomes : It synthesis protein, and ER sent these protein in various part of the cell. Where as SER helps in the manufacture of fats.

• Golgi apparatus : it is found in most cell. It is another packaging organelle like the endoplasmic reticulum. It gathers simple molecules and combines them to make molecules that are more complex.

• Lysosomes : It is a kind of waste disposal system of the cell. It helps to keep the cell clean by digesting any foreign material.

• Mitochondria : It is known as the power house of the cell. The energy required for various chemical activities headed for life is released by mitochondria in the form of ATP (adenosine-tri-phosphate) molecules.

• Centrioles : It is a micro-tubular structure; centrioles are concerned with cell division. It initiates cell division.

• Plastids : These are present only in plant cells. There are two types of plastids:-chromoplastes (colour plastides) and leucoplast (white or colourless plastids)

Some important facts regarding cells:

• Nerve cells in animals are the longest cells.
• Smallest human cell is red blood cell.
• Largest human cell is female ovum.
• The single largest cell in the world is of an ostrich.
• The smallest cells are those of the mycoplasma.
• Every minute about 3 millions cells in our body die.
• Sieve tube in plants and the mature mammalian red blood cells do not have a nucleus.
• The red blood cell carries respiratory gases.

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