Allen Study Material For Neet

Cell Introduction

 Today we learn about the introduction of cell – the building block of any living organism. It also discusses about cells of different shapes, sizes, types.

Just like a house is made of bricks, our body is made up of cells. So, we can say cell are the building block of our body. And both the bricks in the building and cells in our body are the basic units of cells.

What exactly is the cell -

Let us see about what is cell...

In 1665, robert hook observe a slice of cork under a microscope. The cork is actually a bark of a tree. He notice that it was made up of small box-like units. Each box was separated from its neighbor by a wall.He coined the term cell for each box. You know what hooke observed as boxes over-selves in the cork.

Where actually the dead cells as the cork was made from the bark of a tree thus cell was discovered accidentally, Later scientists came to know that all living things are made of such microscopic small units which are cells only.

From unicellular organisms like amoeba to a large blue whale every living organism is made up of cells. You know the number of cells are not same in all the organisms. There are many organism made of  one tiny cell only. Like the bacterium.

Cell introduction

Few of them are small as millionth of  a meter. On the other side a mouse have more than billion cells.

1 Billion as we know is equal to 1000 millions. You know our body as trillions of cells. One trillion as we know is 1000 billion. Which is a very large number. 

 Do All The Organisms Have Same Shape And Size - 

No, surprisingly but true the egg of a hen represents a single cell and it is big enough to be seen by the unaided eyes. The white material that surrounds the yellow part in the egg is albumin, Which solidifies on boiling while, the yellow part is called yolk.

You know yolk is the part of single cell and this single cell can be observed without any magnifying device. Surprising isn't it. The size of all the cells are not same. The smallest cell is 0.12-0.5 micro meter. In bacteria, If we divide a meter into million equal parts then one part is a micrometer. So imagine how small a bacterium is.

On the other hand the cell in the egg of ostrich can be as big as 170 millimeter by 130 millimeter.

That's quite huge. Not just the number and size  even the shapes of cells are different. The red blood cells of a blood are spherical that is round in shape. Few cells look like spindle that is they are pointed at both the ends. For example our muscle  cells.