Cell the unit of life notes for neet

 

Cell: The Unit of Life  


Introduction

Unicellular organisms are capable of

(i) independent existence

(ii) performing the essential functions of life.

Anything less than a complete structure of cell does not ensure independent living. Hence, cell is the fundamental structural and functional unit of all living organisms.

Anton Von leeuwenhoek first saw and described a live cell. Robert Brown later discovered the neucleus. The invention of the microscope and its improvement leading to the electron microscope revealed all the structural details of the cell.

 


Cell theory

Study of form, structure, and composition of cell is called cytology.

 • Cell is the structural and functional unit of life. In unicellular organism (amoeba, paramecium, incentive bacteria), single cell perform the all essential functions of life.

 • In multicellular organism, different kinds of tissues perform different function and have division of labour.

 • Melthias Schleiden and Theodore Schwann (1938) proposed the cell proposition

a. All living organisms are composed of cells and products of cells.

b.All cells arise from pre-existing cells. Prokaryotic cells Eukaryotic cells.

 


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An overview of cell

 Shape and size of cells varies greatly according to their position and function. Mycoplasma is the lowest cell and largest insulated cell is the poltroon egg. The shape of cell may be blockish, columnar, polygonal, thread like or irregular.

 


 Prokaryotic cells

Prokaryotic cells are represented by Bacteria, Blue green algae, Mycoplasma and PPLO. They multiply fleetly and vary in size greatly.

·        Bacterial cells may be Bacillus ( rod shaped), Coccus ( globular), Vibrio (comma- shaped) and Spirillum ( curl).

·        All prokaryotic cells have cell wall girding the cell membrane except in Mycoplasma. Inheritable material is naked.

·        The plasmid DNA, in some bacteria provides some special features like resistance to antibiotic.

·        Cell organelles like Mitochondria, Golgi bodies etc. are absent in prokaryotes. A technical discerned cell membrane called Mesosome is the specific of prokaryotes.

·        In bacterial cell a chemically complex cell envelope is present, which correspond of three layers. The remotest is Glycocalyx, middle one cell wall and inner inmost is the cell membrane.

·        Glycocalyax may be as loose jacket in some bacteria called slime subcaste. In some other bacteria Glycocalyx may be thick and tough called capsule.

·        Plasma membrane issemi-permeable having mesosome in form of vesicles, tubules and plates. They help in cell wall conformation, DNA replication and distribution to daughter cells.

·        Motile bacterial cell contain flagella, which is composed of hair, hook and rudimentary body. Pili and fimbriae are the other face structure that help the bacteria in attach with host and other substance.

·        In prokaryotes, ribosome are attached with cell membrane having two sub-units – 50S and 30S to form together 70S prokaryotic ribosomes.

·        Ribosomes are point of protein conflation. Ribosomes attached with mRNA to form a chain called polyribosomes.

·        Reserved accoutrements in prokaryotic cells are present in cytoplasm as cell addition bodies, which may contain phosphate, grains, glycogen grains etc.

·        Gas vacuoles are plant in blue green algae and grandiloquent and green photosynthetic bacteria.


 Cell Structure and function NEET notes PDF

 

Eukaryotic Cell

Eukaryotic cells are present in Protista, plants, Creatures and Fungi. Cytoplasm is divided into chambers due to presence of membrane bounded organelles.

·        The cells contain well systematized nucleus with nuclear membrane. The inheritable accoutrements are arrangerd in chromosomes.

·        Plants cells differ in having cell wall, plastids and large central vacuole as compared to animal cells. Animal cells have centrioles, which are absent in plants cells.

·        Cell membrane is composed of lipids and that are arranged in bilayer. A lipid element is substantially composed on phosphoglycerides. Laterly it was plant that protein is also present in cell membrane. Rate of protein and lipids varies in different cells.

·        Membrane protein may be integral or supplemental. Integral protein remains buried in membrane but supplemental protein falsehoods of face.

·        Songster and Nicholson (1972) proposed fluid mosaic model. According to this model thequasi-fluid nature of lipid enables side movement of within the bilayer of lipids.

·        The main function of plasma membrane is the transport of motes across it.


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·        The movement of water from advanced attention to lower attention by prolixity is called osmosis.

·        Cell wall is present in plants cells and fungi. Algae have cell wall made up of cellulose, galactans and minerals like calcium carbonate. In other plants it consists of cellulose, hemicellulose, pectin and proteins.

·        Primary cell wall of youthful plants is able of growth, which dwindle in mature cells. Secondary cell wall is formed on inner side of the cells.

·        Plasmodesmata connect the cytoplasm of bordering cells. Endomembrane system of cell includes endoplasmic reticulum, golgi complex, lysosomes and vacuoles.


Also check: 


Endoplasmic Reticulum are the tubular haphazard structure scattered in the cytoplasm.

 (i)  Rough endoplasmic reticulum bears ribosomes on its face. RER is involved in protein conflation and stashing.

 (ii) Smooth endoplasmic reticulum doesn't bear ribosomes on its face. SER is involved in lipid conflation and steroidal hormones.

 

·        Golgi apparatus was first observed by Camillo Golgi in 1898 near nexus. They consists of numerous flat, slice- shaped sacs or cisternae staked resemblant to each other.

·        Golgi apparatus performs the function of packaging of accoutrements and its transportation. A number of protein synthesized by ribosomes are modified in cisternae of golgi apparatus. Golgi apparatus is the point for conflation of Glycoprotiens and glycolipids.

 

·        Lysosomes are membrane bound vesicular structure formed by process of packaging in the Golgi apparatus. They're rich in hydrolytic enzyme-lipase, protease, carbohydrases active at acidic PH. These enzymes are able of digesting carbohydrates, proteins, lipids and nucleic acids.


 Cell Biology notes PDF

·        

     Vacuoles are membrane bound space plant in cytoplasm water, tire and excretory product bounded by single membrane. They form contractile vacuole and food vacuole in numerous organisms.

·        Mitochondria double membrane bound structure with the external membrane and inner membrane dividing its lumen in two chambers membrane forms a number of infoldings called cristae towards the matrix.

 

 Two membranes have own specific enzyme.

·        Mitochondria are spots for aerobic respiration. They produce cellular energy in form of ATP so, they're called power house of the cells. The matrix of mitochondria also contain indirect DNA motes, a many RNA motes, ribosomes and factors of protein conflation.

 

·        Plastids are plant only in plants cells and Eugleoids having specific colors to give colours toplants corridor.




 

·        Chloroplast contains chlorophyll that traps solar energy for photosynthesis. Chromoplast provides unheroic, orange and red colours to different corridor of plants.


Cell cycle and cell division NEET notes 

·        

Leucoplasts are colourless plastids that store food, amyloplasts (carbohydrates), elaioplasts (canvases) and aleuroplasts (proteins).

 

·        Chloroplasts are double membrane structure. The space limited by inner membrane is called stroma. Thylakoids are present in stroma as heaps like the piles of coins called grana.

 

·        Stroma contain enzyme for conflation of protein and carbohydrates. Double beachfront indirect DNA and ribosomes are also present in stroma.


 Cell cycle and Cell division Handwritten Notes

·        

Ribosomes are grainy structure of 80S.

·        Centrosomes is an organelles containing two spherical structures called centrioles. Each centrioles is made up of 9 fibrils of tubulin protein. Central corridor of centriole is called mecca and supplemental fibrils are called spokes.


 RELATED POSTS:

·       

Nucleus has largely extended, elaborate nucleoprotein fibres called chromatin, nuclear matrix and nucleoli. The external membrane is nonstop with endoplasmic reticulum and bears ribosomes.

Plastids Chloroplast (contain chlorophyll and caratenoids) Chromoplast ( contain carotene and xanthophylls) Leucoplast (colourless plastids).

 




·        The chromatin accoutrements change into chromosome during active cell division consists of DNA and histone proteins.

Every chromosome has a primary condensation or the centromere, on the sides of which slice shaped kinetochores are present.

·        On the base of position of centromere chromosomes are of following types-

 Metacentric, Sub-metacentric, Acrocentric ,Telocentric.




·       

Some chromosomes have non-staining secondary compression at certain position. This give a small scrap called satellite.

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