Cell class 9th chapter 1 biology cell is basic structure and functional unit of life

Cell

★ cell :- cell is that structure and functional unit of life.

It can perform all the life process independently.

★ characteristics of cell :- same are the building block of plants and animals.

Every organism starts its life as a single cell.

A cell is capable of independent existence and perform all the basic functions of life.

Many cells together form a tissue and many tissue together form an organ.

The organs work together as a system and form an organism.

★ Types of cells :-

1) prokaryotic cell

2) Eukaryotic cell

★ difference between prokaryotic cells and Eukaryotic cells given below:-

★ on the basis of number of cell organism are classified into two groups:-

1) unicellular organism:- an organism that consists of only one cell is called unicellular organism.

In this type of original all the activities are performed by a single cell,so there is no division of labour.

The life of unicellular organism is short.

Ex:- amoeba,paramecium,bacteria,yeast etc

2) multicellular organism:- an organism consists of more than one cell.

In this type of different activities are performed by different cells and tissues so, division of labour is present.

The lifespan of multicellular organism is long.Ex:- algae fungi,higher plants,animals etc

★ History of cell:- cell was discovered by Robert in 1665.

He observed the cell in a cork slice with the help of self made microscope.

Nazar that cop section is made up of a large number of small boxes or compartment forming a honeycomb like structure. he called the compartment --------- - cell(latin:- cellular) means small boxes.

antonvan leeuwenhoek (1674) discovered the free living cells in pond water.

Robert brown described nucleus in the cell of orchid roofs.

★ cell theory:-

Schleiden and schwann collectively formulated cell theory.

Rudolf virchow gave phrases " omgis cellulae " it means all cell arise from pre existing cell.

This principle was also added to cell theory.

★ postulates of cell theory:-

1) cell is the basic unit of structure of all plants and animals.

2) cell is the basic unit of function as all the metabolic reaction takes place inside the cell.

3) every organism starts its life as a single cell.

4) all living cell arise only from preexisting cell.

★ Exception of cell theory:-

Virus:- it is not the cell.

Bacteria & blue green alage (BGA ):- these are not a true cell.

★ cell size :- the size of silver price in broad range from said visible with naked eye while some still visible only with microscope.

Small cell:- mycoplasma (pplo) size is

0.1 - 0.15 μm in diameter.

Largest cell:- ostrich egg size is 170 -130 mm in diameter.

Longest cell:- nerve cell size is 1metre in length.

★ cell shape:- different cell perform different function and differentiate in different organism.

Some cells like amoeba,WBC can change their shape where as most plants and animals have fixed shape.

Spherical or oval -- ovum/egg

Polygonal -- liver cell

Cuboidal -- bone cell

Spindle -- smooth muscle cells

Cylindrical -- xylem, phloem.

★ structural organisation of the cell.

The basic component of the cell icsil membrane cytoplasm and nucleus.

Cell-cell wall = protoplasm. It means cytoplasm & nucleus combinely called protoplasm.

★ cell membrane :- it is outermost covering of cell.

It separates the cell content from the external environment.

It is formed of lipid and protein.

It is present in plant and animal cell.

Plasma membrane is living,thin,elastic & selectively permeable membrane.

★ structure of cell membrane:-

★ fluid mosaic model (ice berg model)

Singer and Nicholson proposted this model.

According to this model thin membrane consist of two layer of phospholipid molecules in which protein molecules are embedded.

In this,phospholipid and protein are arranged as mosaic.

Phospholipid molecules have their polar heads directed outward,non polar tail pointed inward.

★ Types of protein:-

1) Extrinsive protein/peripheral protein:- this protein located superficially.

2) Intrinsive protein/Integrated protein:- this protein is is embedded in phospholipid matrix.

★ function of cell membrane:-

1) regulate the movement of molecules inside and outside the cell.

2) flenibility of the membrane enable the cell to engulf food which is known as endocytosis.

eg:- in amoeba

3) it gives definite shape to the cell.

4) it allows movement of resistance from higher concentration to lower concentration which is known as diffusion.

5) being selectively permeable movement of water molecules through the selectively permeable membrane is known as osmosis.

★ how substance move in and out of the cell:-

1) Diffusion:- movement of electrons from higher concentration to lower concentration and uniform concentration is achieved.

During diffusion no energy required because diffusion is passive process.

2) osmosis:- the moment of water from lower concentrated solution to higher concentrated solution semipermeable membrane is called osmosis.

The movement of water molecules from its higher to its tower concentration semipermeable membrane is called osmosis.

★ when plant or animal cell placed in different solutions:-

1) Hypertonic solution:- when cell placed in hypotonic solution then water moves out from thebcell and cell become shrink and decrease in volume this process is called enosmosis.

2) Hypotonic solution:- when cell placed in hypotonic solution then she gets extra water from the solution and gets targeted and volume of sale in this process is called endismosis.

3) Isotonic solution:- when sale please din isotonic solution than equal amount of water moves in word as well as outworx so no change in volume occurs.

★ passive & active transport:-

1) Passive transport:- the movement of molecules along the concentration gradient by the process of diffusion or osmosis is called passive transport.

In passive transport no expenditure of energy occurs.

2) Active transport:- the movement of molecules against the concentration gradient is called active transport.

In this process expenditure of energy occurs.

Q. Write difference between osmosis and diffusion.

Sol:-

★ cell wall :- it is outermost rigid covering a plant cell,bacterial cell and fungal cell.

★ function of cell wall :-

1) it provides a definite shape,protection and mechanical support to the cell.

2) it gives strength to the aerial parts of the land plants.

3) it forms a skeletal framework of plants.

4) it contracts the osmotic pressure and prevent cell bursting.

★ Nucleus:-

--> it is a spherical double membrane structure present in the Eukaryotic cell.

--> it is usually located at the centre of animal cell and at periphery in plant cell due to presence of large vacuole.

--> it is discovered by Robert brown in 1831.

--> generally it is one in number in a cell but sometimes it may in two or three in number called 2 Binudeate ( Diakaryotic ) or multinucleate respectively

--> exceptionally some cells do not have nucleus like mature mammalian RBC, sieve tube of phloem.

★ nucleus consists of following structure:-

1) Nuclear envelope :- it is the outer envelope of nucleus which is made up of lipoprotein ( same as plasma membrane ).

--> nuclear envelope consists of two membrane:- a) outer membrane

b) inner membrane

--> the space between the two membrane are perinuclear space.

--> the outer membrane is continuous with endoplasmic reticulum.

--> the nuclear envelope perforated by several minutes pore called nuclear Pore which allows the exchange of material between nucleus and cytoplasm.

2) Nucleoplasm:- the nucleus is filled with a transparent semi solid substance called Nucleoplasm.

--> it contains nucleic acid (DNA and RNA),protein,Enzymes,nucleolus and chromatin thread.

3) Nucleolus:- nucleolus is a dense spherical body present with in the nucleus.

--> nucleolus is without membrane.

--> ribosomes are synthesized in nucleus.

4) Chromatin thread:- it is thread like structure present in nucleus.

--> it is formed of nucleic acid (DNA) and protein.

--> during cell division it is condensed into short rod shaped structure called chromosome.

⬇️

Hereditary vehicle.

--> chromatin thread is made up of DNA and functional segment of DNA is called gene.

--> genes carry information for protein synthesis which is responsible for development of characters.

--> jeans are called Hereditary unit and DNA is known as Herediatory material.

★ function of nucleus :-

1) it controls all the activity of cell to Nucleus is also called control room of cell.

2) nucleus also control the cell division.

3) it stores genetic material DNA and RNA which is responsible for transmission of characters from one generation to another.

4) it health information of ribosomes and different types of RNA need for protein synthesis.

★ cytoplasm :- the jelly like fluid present between cell membrane and nuclear membrane.

--> cytoplasm contain mainly water and salt.

--> it contains protein,carbohydrates,lipids and many Enzymes which is responsible for different metabolic reaction.

--> cyto plants mainly divided into two parts

1) liquid part ( cytosol )

2) solid part ( cell organelles )

--> plants contain many cell organelle like mitochondria, Golgi bodies, ribosomes, plastid,lysosome,Golgi complex, Endoplasmic reticulum & vacuole etc.

★ Endoplasmic reticulum:-

it is complex network of channel bound by membranes present in Eukaryotic cell.

--> it arise from outer nuclear membrane.

--> in some places these channels are connected with plasma membrane at one end and with a nuclear membrane at other end forming continuous channel.

--> endoplasmic reticulum is absent in prokaryotic cell and mature mamallion RBC.

Endoplasmic reticulum occurs in two forms:-

1) smooth Endoplasmic reticulum :-membrane of smooth endoplasmic reticulum is smooth because Rambo sound are not attached to them.

2) Rough endoplasmic reticulum :-

Ribosomes are attached to the surface of rough endoplasmic reticulum store membranes of Endoplasmic reticulum have grainy or rough appearance.

★ son of Endoplasmic reticulum:-

1) provides mechanical support to the cell.

2) endoplasmic reticulum forms channel dish channel form intercellular transport system.

3) it participated in the formation of cellular nuclear membrane after every cell division.

4) smooth endoplasmic reticulum takes part in the formation of storage and lipid.

5) rough endoplasmic reticulum helps in synthesis of protein.

★ Golgi Complex:-

Golgi apparatus was described bike camillo Golgi in 1898.

--> it is special type of smooth endoplasmic reticulum.

--> it is present in all Eukaryotic cell except mature mammalian RBC.

--> Golgi complex is in the form of parallel arranged interconnected flattened sacs called cristernae. With many tubules, vesicles and vacoules lying above the nucleus in animals cell and scattered in cytoplasmic matrix.

--> in plant cell several freely distributed subunits of Golgi complex are present called dictyosome.

Golgi complex as two distinct faces

1) crisface/forming face

2) Transface/maturing face

★ function of Golgi complex:-

1) it is a factory in which protein sreceived from the endoplasmic reticulum are furth processed and started for transport to there eventual destination.

2) synthesis of cell wall,plasma membrane, lysosomes,glycoprotein,polysaccharide etc

3) transporting lipids around the cell.

4) secretion of mucus enzyme and hormones and storage of secretory products.

5) formation of cell during cell division in plant cell.

★ Mitochondria :-

It is also known as powerhouse of the cell and found in both plant and animal cells.

--> mitochondria is a double membrane cell organelle.

--> The other membrane is smooth where as inner membrane is folded into finger like projections called cristae.

--> the space within the mitochondria is called inner mitochondrial chamber which is filled with jelly like proteinaceous substance called matrix.

--> Matrix contain respiratory enzymes ribosomes and circular DNA.

--> mitochondria have their own genetic material (DNA,RNA) which is different from nuclear genetic material.

--> they can replicate on their on therefore they are called semi autonomous cell organelles.

--> cristae of Mitochondria consist small rounded body known as F1 particle or oxysome for ATP synthesis.

★ function of Mitochondria:-

1) oxidation of glucose completes here so, energy is released, which is store in the form of ATP so, mitochondria is also known as powerhouse of the cell.

★ plastids:-

It is Largest cell organelle present in plant cell only.

--> it is also double membrane cell organelle.

--> it is generally ovel, spherical and discoild in shape.

Plastid is basically are of three types:-

1) chloroplast

2) chromoplast

3) leucoplast

1) Chloroplast :- chloroplast contain green colour pigment called chlorophyll which is needed for synthesis of food by the process of photosynthesis.

--> it is also double membrane cell organelle.

--> space inside the membrane is filled with Matrix call stroma.

--> stroma consists stalks of membrane bounded sacs called thylakoid. The thylakoid are arranged one above another in the form of stack of columns and form granum and unstack membrane bound sac called stroma lamella.

--> photosynthetic pigment (chlorophyll) are present in these thylakoids.

--> chloroplast contain their on DNA, RNA and ribosomes.The synthesis of their own protein and also have the capacity of replication so chloroplast is also known as semi-autonomous cell organelle.

2) Chromoplast :- these contain yellow orange and red pigment.

--> they are present in petals of flower and fruits.

--> it has colour pigment

Xanthophyll -- yellow

Carotene -- orange and red

3) Leucoplast :- it has no pigment show it is colourless plastids.

--> leucoplast Stored many substances such as :-

Amylopast -- stores starch

Aleuroplast -- stores protein

Elaioplast -- stores lipid and fat

★ function of Plastids :-

1) photosynthesis :- chlorophyll of chloroplast traps solar energy which is used for preparation of glucose (food) by the process of photosynthesis chloroplast is called kitchen of the cell.

2) Gives colour :- chromoplast give attractive colour in flower and fruits for attracting insects and birds for pollination.

3) Storage :- leucoplast is for storage of many substance.

Q1. Write difference between chloroplast chromoplast and leucoplast.

Ans:-

★ Vacuole :-

it is fluid filled membrane bound cell organelle present in cytoplasm.

--> it is filled with water and many substances like minerals,carbohydrates, organic acids and metabolic waste.

--> the membrane around the vacoule is known as tonoplast.

--> generally plant cell contain large vacuole due to which nucleus is pushed towards periphery but in animals cell it is smaller.

★ function of vacoule :-

1) storage -- They store food materials and waste product.

2) osmoregulation and removal of excretory wastes -- vacuoles help in maintaining the water balance and excretion.

3) turbidity & rigidity -- they keep the cell turbid and provide then rigidity and support.

★ Lysosome :-

It is spherical and sac like vesicles bound by a single membrane.

--> it contains several digestive enzymes when these enzymes are released several cytoplasmic organelles are auto digested hence it is referred as suicidal bag of cell.

--> it is found only in animal cells.

★ Function of lysosome :-

1) it protection from bacteria and viruses by digesting them.

2) lysosomes help in intracellular digestion.

★ Ribosomes :- it is smallest cell organelle.

--> it is membrane less cell organelles.

--> it occurs either scattered in cytoplasm or attached to the surface of Endoplasmic reticulum and also present in plastic and mitochondria.

--> and Eukaryotic ribosome is 80s and prokaryotes ribosomal 70s.