Question

Can anyone send me notes of the chapter -The fundamental unit of life (class -9) ?

Answer 1

$\huge \boxed{heya} \huge \blue{dahi}$
___________▪▪▪□■□■□▪▪▪___________

Cell = Cell is the basic structural and functional unit of life,...

'The fisrt person to see cell was an English scientist, Robert Hooke in 1665. He studied a thin slice of bottle cork under his self-made microscope and observe box like compartments resembling a honey comb.
He called these compartments, the cells.

☆Cell is a latin word for a little room.

cells are of different shapes,sizes,Numbers.
☆Man is estimated to have about 100 trillion cells.

☆Smallest cell= Mycoplasma.
☆Largest cell = Ostrich's egg.
☆Largest cell in human body is :Ovum
☆Longest " " " " " :Neuron.
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$\bold{cell \: organelles \: ....} structure \: and \: functions$
i.)Plasma or Cell Membrane ,
□Structure = It is outermost covering or membrane that encloses the contents of a cell.

□ it is less than 1/10,000 mm in thickness.

FUNCTION :

□It seprates the contect of a cell from its external enviroment .
□It protects the inner cell contents, like a mechanical barrier.
□It is a selectively permeable. i.e it allows some ions & other substances to pass through but not others.
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ii.)NUCLEUS : 'Brain of the cell'

STRUCTURE : □It is generally spherical or oval in shape.
□Nucleus has some important parts :i.)Nuclear membrane, ii.)Nucleoplasm iii.)Chromatin material iv.)Nucleolus (plural : nucleoli)

FUNCTION :

□It contains hereditary information of the cell .

□All instruction for developement,reproduction ,behaviour are stored in the coiled structures called chromosomes.Hence nucleus is also responsible for reproduction,as well as transmission of genetic material from one generation to another.

□it controls cellular activites.
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iii.)cytoplasm :

STRUCTURE: it is jelly like substances in which various cell organelles are suspended.
□It contains various kinds of biochemical like : Salts, sugars ,amino acids and proteins.

FUNCTION :It helps in exchange of materials between cell organelles.
□it acts like a site of chemical reaction like glycolysis in cell.
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iv.)CELL WALL :
STRUCTURE : It is rigid covering present outside the plasma membrane.

□ It is made up of cellulose (a fibrpus polysaccharide)

FUNCTION :It protects the plasma membrane and inner contents of the cell.
□It gives shape to the plant cells.
□It prevents osmotic bursting of the cell.

$\boxed{only \: present \: in \: plants \: cell}$

v)ENDOPLASMIC RECTICULUM :
STRUCTURE :It is a complex system of membranous sacs running through the cytoplasm.
□Their lumen is filled with fluid.

THSES ARE OF 2 TYPES :

1)SMOOTH RECTICULUM :(SER) (without ribosomes and so has smooth membranes)

2.)ROUGH ENDOPLASMIC RECTICULUM :
(SER)..It has ribosomes attached to the surface and so the membranes have a rough and granular surface.

FUNCTIONS:
□It gives mechanical support by forming a network in cytoplasm.
□SER synthesises lipids and steroids.
□RER helps in the transport and synthesis of protiens (because chromosomes on its surface)
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vi) GOLGI APPARTUS OR COMPLEX ..

STRUCTURE :IT is in the form of a series of flattented membranous sacs called cisternae,tiny vacuples called vesicles & large vacoules.
□Cristernae are slightly curved and enclose a cavity inside.
□The cristernae are slightly curved & enclose a cavity inside.

FUNCTION :It stores , condenses & packages the materials synthesised in ER.
□It plays important role in the formation lf lysosomes & peroxisomes.
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LYSOSOMES :

STRUCTURE : they are membrane-bound vesicles that occur in all animal cells only in few plant cells.
□They are bounded ny a single membrane.
□They could be spherical to irregular in shape.
□They contain powerful digestive enzymes which rapidly breakdown proteins,lipids,carbohydrates,nucleic acids.

FUNCTION : They digest harmful & foreign material like : bacteria,germs & viruses .
thats why they are called digestive bags of the cell.
□They helps in removing unwanted structures within a cell.They digest old worn-out cell organelles & make way for the formation of new ones.
□They brings self destruction of cell by releasing their enzymes with in cell.
In such cases they are called suicidial bags.
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VIII)MITOCHONDRIA..

STRUCTURE :They are usually sausage-shaped by two membranes.
□Each mitochondria is bounded by two membranes.□Outer one js mooth,while inner one is folded into fingers like projections called cristae.

□It contains numbers of enzymes required for oxidation of food.

☆FUNCTION :They are sites cellular respiration or oxidation of food.

□It is knw as 'Power house 'because during oxidation ,energy released in stored in the form of ATP (Adenosine triphosphate)Molecules.
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ix)PLASTIDS:(found only in plant's cells )
STRUCTURE :surrounded by 2 membranes.
□They are 3 types :
》Leucoplastsa(colourless)
》Chromoplasts(contain red,yellow or organe pigments)
》Chroloplasts(contain chlorophyll)