cell -structure and functions

CELL- STRUCTURE AND FUNCTIONS

INDEX1. Introduction2. Basic structure of cell3. Discovery of cell4. Cell theory5. Unicellular & Multicellular organism6. Different size of cells7. Different shapes of cells8. Structure of cell 8.1Cell membrane 8.2 Cytoplasm 8.3 Nucleus 8.4 Cell organelles

(i)Vacuole(ii) Mitochondria(iii) Ribosomes(iv) Golgi Bodies

9. Prokaryotic and Eukaryotic cells10. Comparison between plant and animal cell Video Did you know Recapitulation Home Assignment

Students things around us are either living or non –

living –do you ever imagine how these living things made from, what is the

basic unit which composed the living organism.

1.INTRODUCTION Cell is the basic unit of any living

system.

Like ,Brick is the basic structure unit of a house, Same as like Cell is the basic structural unit of a human body.

Onion peel cells under the microscope.

Grouped to form

Grouped to form

Organized into

And make up the complete

Do you know?

Systematic Organization of human body.

2.Basic structure of cell

3.DISCOVERY OF CELLWho discovered cell and how?

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4.CELL THEORY

1.All living cell

things are composed of

cell.

2.Cells are made

up of pre-existing cells.

3.Cell is the

structural and functional unit

of life.

Do you know –Organisms show Variety

In Cell Number Shape Size

5.Classification of Organisms according to no. of cells

1. Unicellular 2.Multicellular

Amoeba , the single cell organism.

Animals, the multicellular organisms.

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6.Size of cellThe size of cells in living organisms maybe as small as a millionth of a meter (micrometer or micron) or may be as large as a few centimeters.

Largest cell

The smallest cell is 0.1 to0.5 micrometre in bacteria. The largest

cell measuring 170 mm ×130 mm, isthe egg of an ostrich.

Do you know?

7.Shapes of cellDifferent cells have different shapes .The shape of a cell is related to its functions and locations.

Round elongated shape

Spindle shape with pointed ends.

8.STRUCTURES OF CELL

8.1Cell membrane/plasma membrane

Cell wall(an outer thick layer in cells of plantscalled cell wall.)

Plasma membrane

FunctionThis additional layersurrounding the cell membrane isrequired by the plants for protection.Plant cells need protection againstvariations in temperature, high windspeed, atmospheric moisture, etc.

Function• It forms the outer

boundary of cell which is thin and delicate

membrane and gives the shape and size to the cell.• It allows only certain selected substance to

enter and leave the cell.

8.2CytoplasmVarious other components, ororganelles, of cells are present in thecytoplasm. These are mitochondria, golgibodies, ribosomes, etc.

Mitochondria

Golgi bodies

Nucleus

Ribosomes

Cell organelles

8.3NucleusI am the oval shaped body floating in the cytoplasm. I am responsible for the vital

functioning of the cells.

I consist of nuclear membrane, nucleoplasm, nucleolus, chromosomes

and genes.

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8.4Cell organelles

These are components, small cytoplasmic bodies, or

organelles, of cells that present in thecytoplasm. These are mitochondria, golgibodies, ribosomes, etc.Mitochondria

LysosomesEndoplasmic reticulum

Golgi Apparatus/bodies

Ribosomes Cell Organelles which are embedded

in the cytoplasm.

More cell organelles and their functions:- (i) Vacuole

I resides only in the plant cells. The blank-looking structure in the cytoplasm is called vacuole. Largevacuoles are common in plant cells.Vacuoles in animal cells are muchsmaller.

(ii)MitochondriaI am

powerhouse of the cell. I store

energy in the form of ATP.

(iii) Ribosome

It helps in protein synthesis.

Protein factory of cell

(iv)Golgi bodies

Its function is the packaging of proteins .

It helps in the synthesis of food (photosynthesis)due to the presence of chlorophyll. Green coloured plastids are

called chloroplasts. They provide greencolour to the leaves.

9.On the basis of nucleus ,cells are of two types:-

Prokaryotic cells

Eukaryotic cells

prokaryotes(pro :primitive; karyon : nucleus) The cells havingnuclear material without nuclearmembrane are termed prokaryoticcells.. E.g.are bacteria and blue green algae.

Eukaryotes(eu :true; karyon: nucleus) that contain well organised nucleus. E.g. are animal and plant cells.

flagella

Nuclear material without nuclear membrane

cytoplasmRibosome's

Difference between Prokaryotes & Eukaryotes

10.Comparison between plant and animal cell

Let’s summarize through the Video

. The cells in the outermost layer of our skin are dead. An averageadult carries around about 2 kg of dead skin. Billions of tinyfragments of the skin are lost every day. Every time you run yourfinger on a dusty table, you shed a lot of old skin.

DID YOU KNOW?

RECAPITULATIONGive the one word answer.

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PracticeLETS PLAY A CROZZ WORD PUZZLE

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HOME ASSIGNMENT1.A cell requires water, minerals and

other nutrients to survive. It is covered with a membrane. How do these things reach inside the cell ?

2.Why are chromosomes called heredity vehicle?

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ROBERT HOOK IN 1665 OBSERVED

SLICES OF CORK IN MICROSCOPE

Robert took thin slices of cork and observed them under a microscope. He noticed partitioned boxes or

compartments in the cork slice. These boxes appeared like a honeycomb. He also noticed that one box was

separated from the other by a wall or partition. Hooke coined the term ‘cell’ for each box.

Unicellular(uni : one; cellular :

cell)

•Consist of only one cell.•A single-celled organism, like amoeba, captures and digests food, respires, excretes, grows and reproduces. Similar

Multicellular(multi :

many; cellular : cell)

•Consist of cells numbering from few to billions.•Multicellular organisms like human beings carried out functions by groups of specialized cells forming different tissues.

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Inside the nucleusNuclear membrane-It surrounds

the nucleus that controls passage of selected material in and out of

the nucleus.Nucleoplasm-Dense fluid in the

nucleus.Nucleolus-It’s a spherical body that contain RNA( Ribo nucleic

acid).Chromosomes- these a have

thread like structure which are composed of DNA( Deoxyribo

nucleic acid ) which carry genes(the basic units of

hereditary ).

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References NCERT science textbook for class VIII Google gif Animated Images hhttps://www.google.co.in/search?

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