Fundamental UNIT OF LIFE : CELL - Class 9 PDF Download

CELL :THE THEORY|

CELL:THE FUNDAMENTAL UNIT OF LIFE

1.1 INTRODUCTION

• The discovery of cell was done by SIR ROBERT HOOKE

• While examining the slice of cork reassembled the structure of honeycomb,consisting many of the little compartments as “cell” - which is a latin word gives the meaning as a room (little room)

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1.2 WHAT ARE LIVING ORGANISMS MADE UP OF?

• When we are watching any of the microorganisms or cell then we have many of the questions in our mind related to the figure, but the factful question is that what are living organisms made up of?, as we see the structures present on the cell body, so, what are the structures made up of?

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• The structure of an Onion Bulb!, as a big structure,visible under the microscope these structures are called CELL, not only onions, but all the organisms we see around us are made up of cells, there are many of the single celled which live on their own, but most of the organisms are Multicellular

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• The shape and size of the cells are related to perform specific functions as they perform .i.e. Amoeba have changing shapes

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• We can see a division of labour also in a single cell as well as in the multicellular organisms .i.e. As a human body has a heart to pump blood , stomach to digest food, lungs to breath, in fact each such cell has got certain specific organ to perform various functions these organs are known as cell-organelles

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1.3 WHAT IS CELL MADE UP OF? WHAT IS THE STRUCTURAL ORGANISATION OF CELL?

HOW A CELL IS ORGANISED?

       If we study a cell under a microscope, we would come across three features in almost each and every cell:

• PLASMA MEMBRANE

• NUCLEUS

• CYTOPLASM

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1.4 PLASMA MEMBRANE OR CELL MEMBRANE

• This is the outermost covering of cell.

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• It seperates the contents of the cell from its external environment

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• It permits the entry and exit of only few of the materials and minerals such as O2 and CO2

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• So it is also known as selectively permeable membrane

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• Some substances like O2and CO2can move inside and outside of the cell by the process known as diffusion

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• There is a spontaneous movement of a substance

                                                                                                                                                                                                              SINCERELY 

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