What is Cell? (in computer)
In computer we use various kinds of spreadsheet, specially in microsoft excel. A cell is the intersection between a row and a column on a spreadsheet In spreadsheet applications, a cell is a box in which you can enter a single piece of data. The data is usually text, a numeric value, or a formula. The entire spreadsheet is composed of rows and columns of cells. A spreadsheet cell is analogous to a field in database management systems. Individual cells are usually identified by a column letter and a row number.
In DVD, a cell is a unit of playback of real-time data. Each cell is identified by a unique set of numbers.
In Short cell is called cellular phone.
Cell Biology is the sub discipline of biology that studies the basic unit of life, the cell. A cell is the very smallest unit of living matter. Cells are the structural and functional units of all living organisms. Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular, or have many cells—an estimated 100,000,000,000,000 cells! Each cell is an amazing world unto itself: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. All living things including plants and animals are made up of cells. Cells are made of atoms, which are the smallest units of matter.
Important Events of Cell Biology
There have been many significant events in history of the development of the field of cell biology as it exists today. Here are some of the major events:
• 1655 – Robert Hooke gives first description of a cork tree cell.
• 1674 – Leeuwenhoek views protozoa.• 1683 – Leeuwenhoek views bacteria.
• 1831 – Robert Brown was first to identify the nucleus as an important cell component.
• 1838 – Schleiden and Schwann introduce what would become the Cell Theory.
• 1857 – Kolliker describes mitochondria.
• 1869 – Miescher isolates DNA for the first time.
• 1898 – Golgi discovers the Golgi apparatus.
• 1931 – Ruska builds the first Transmission Electron Microscope.
• 1953 – Watson and Crick propose structure of DNA double-helix.
• 1965 – First commercial Scanning Electron Microscope produced.
• 2003 – Human genome DNA sequence draft completed.
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Types of Cell
On the basis of the organisation of nucleus, cells can be divided into two types –
1. Prokaryotic cell.
2. Eukaryotic cell.
Now I shall discuss in details about this two types of cell –
a) Prokaryotic cell:
A prokaryotic cell does not contain any true nucleus. This is why it is called a cell with a primitive type of nucleus. The term nucleotide fits nice in this case. Nuclear materials in a prokaryotic cell are not surrounded by any nuclear membrane. They are dispersed in its cytoplasm. Though the cell organelles such as mitochondria, plastids, endoplasmic reticule etc. are not found in a prokaryotic cell, ribosomes are present in it. Only the unwrapped DNA constitutes the chromosomal structure of a prokaryotic cell. For example, blue green algae and bacteria are constituted of this type of cell.
b) Eukaryotic cell:
In this type of cell, nucleus is well structured that means nuclear materials are well organised and surrounded by a nuclear membrane. Chromosomes are organised with DNA, histone protein and other components. From algae to higher flowering plants and from Amoeba to advanced animals, the basic structural and functional component is eukaryotic type of cell. Along with ribosome, other cell organelles are present in the cell.
On the basis of function, there are two other types of cells: somatic cell and gametic cell.
(1) Somatic cell:
This type of cell takes part in the organisation of the body of an organism. The cell divides through the process of binary fission and mitotic division. Organisms grow in this way. Moreover, cells take part in the organisation of different organs and organ systems.
(2) Gametic cell:
Gametal cells are produced in the organisms in which sexual reproduction and alternation of generations occur. Primordial germ cells divide through meiotic division and produce gametic cells. In a gametic cell, number of chromosome becomes half than that of its somatic type. A new living body is commenced after the fusion of male and female gametes. Half life fuses with another half life to produce a full life. Zygote is the first cell produced after the union of male and female gametic cells.
Zygote undergoes repeated mitotic division to organise a body of an organism.
I conclusion, I hope that every learners will clear about what is cell and type of cell after reading this article.