Plant Cell: Structure, Shape, Discovery, Types.

General Introduction

Cell

There Are many Various Organisms that survive in our Earth, They look very different from each other and their categories or Family are also different such as some organisms belongs to Fungi, some are Protista, Some are reptiles and so on. But One thing is Common among them that is The CELL by which their body is made up of.

The Basic definition of cell is “CELL IS THE FUNDAMENTAL UNIT OF OUR LIFE”. All Living have cell; some contain single cell they are called as UNICELLULAR but some contain multiple number of cell they are called MULTICELLULAR.

UNICELLULARMULTICELLULAR
1). They contain single cell.1). They contain multiple no. of cell.
2). Life Span is short.2). Life Span is long.
3). eg-Protista.3). eg-Human.

Like other organisms, Plants have also life (that is proved by Jagadish Chandra Bose. He also discovered that plants have a definite life cycle, their reproductive system and so many things about plants). so, they also contain Cell and tissue like other organisms. Plants belong to the kingdom Plantae. and They contain eukaryotic cells, that have a true nucleus with specialized organelles that carry out different functions. Plant cells have special organelles known as chloroplasts which helps plant to prepare their foods via photosynthesis process.

Discovery of cell

Robert hooke

Robert Hooke was the first person who discovered The cell  in 1665, which was  described in his book Micrographia. Robert Hooke analyzed that the Cork resembled the structure of Honeycomb that consists of many little compartment. Cork is a substance that is obtain from the bark of Tree. Robert Hooke called these small compartment — CELLS, basically The term CELL is derived from the Latin word which means Little Room. His discovery was important because it showed for the first time that Living organism consists the number of smaller structures or units.

Instruments for study about cell

Microscope

Cells are too small in size so we can’t see them with our naked eyes. Hence cells are studied by using Microscope, Microscopes are High power instruments that are used to see very minute objects. Basically Microscopes are categorized into 2 types.

  1. Light Microscope = Light microscope also known as Compound microscope. Light Microscope contains glass lenses and it uses a beam of light to illuminate the objects. In Light Microscope, Internal vacuum is not required.
  2. Electron Microscope = Electron Microscope was discovered by Knoll and Ruska in 1932. Electron Microscope contains electromagnet instead of glass lenses and also use a beam of electrons instead of light. In Electron Microscope, Internal vacuum is required.

Types of cell

Further cells are categorized into 2 basic types-

  1. Prokaryotic = Prokaryotic are that types of cell that is very small in size i.e. 1 to 10 mm. Prokaryotic cells do not contain any nucleus, contains single chromosome. In Prokaryotic cell, cell division occurs by fission or budding and Nucleolus is absent in Prokaryotic cell.
  2. Eukaryotic = Eukaryotic cells are that types of cell that is greater than prokaryotic cell in size. Eukaryotic cell contain nucleus and also contains more than one chromosome. In Eukaryotic cell, cell division occurs by mitosis and meiosis.

Cell Shape

As we know that cell has two types, Eukaryotic cells and Prokaryotic cell; And the Basic shape of eukaryotic cell is Spherical, But the shape of cell is determined by the function of cell. Fixed shape of cell occurs in mostly plants and Animals. In Unicellular organism, the cell shape is maintained by their plasma membrane and exoskeleton. In multicellular Organism, the shape of cell depends mainly on its functional variation and partly on surface tension, viscosity of protoplasm and Rigidity of the cell membrane; As this way different organisms have different shape of cell.

Cell Size

Generally the Size of the cell is too small because some plants and Animals are too small such that they can not be

Size and shape of cell

seen by our naked eyes. The size of any substance is measured by its diameter; Mostly cell that that are only visible in microscope are only few micrometres in Diameter.

The prokaryotic cell usually range between 1 to 10 micrometre and the Eukaryotic cells are large than Prokaryotic because its cells range lies between 10 to 100 micrometre. The size of Unicellular organism is larger than a typical cell of multicellular organisms. The size of typical cell of multicellular organisms range between 20 to 30 micrometre.

Cell Theory

microscope by Robert hooke

The Term CELL is derived from the Latin word “Cellula” which means a little Room. An English Scientist ROBERT HOOKE (1635-1703). In 1665, he discovered and named the cells, while examining the thin slice of bottle cork under a primitive microscope made by him. Hooke observed cork’s honeycombed structure and called them cell. He published is work in his book “MICROGRAPHIA”.

In 1674, Anton Von leeuwenhoek (1632-1723), A Dutch microscopist, made an improved microscope and By using this microscope he discovered the free living cells in pond water for the first time in 1674. In 1678, He also discovered the sperm and identified the sperm cells of human, dogs, frogs, rabbits, fishes and so on. In 1831, A scottish botanist, Robert brown discovered and named the nucleus in Plant cell. J. E. Purkinje, A czech animal Physiologist, in 1839 gave the term Protoplasm.

The cell Theory is refined further in 1838, when a German biologist, First proposed the idea that Plants  consist cells and In 1855 another German biologist, R. Virchow presented the idea that all cells arises from pre-existing cell.

Honeycomb structure

Thus the cell Theory consists of following Postulates-

  1. All organisms are composed of cells and cell products.
  2. All metabolic reactions take place in cell.
  3. All cell arises from pre-existing cell only.
  4. Every Organism starts its life as a single cell.

Cell Structure

As we know that cell is the basic unit of life, all cells have following Three Major functional Region-

  1. Cell membrane and cell wall
  2. The Nucleus
  3. The cytoplasm

1). Cell membrane or Plasma membrane-

The outer Boundary of cell is known as Cell membrane. Cell wall is present in all cells of Plants, Animals and Micro-organisms. Most cellular organelles such as mitochondria, chloroplast, lysosomes, Golgi apparatus and so on are enclosed by the cell membrane (wall). Plasma or cell membrane is a living, thin, delicate, elastic and semi permiable membrane. It is about 7 nano metre.

Plasma membrane permits the entry and exit of some materials in the cells. Therefore, the plasma membrane is also called selective permeable membrane. There are some advantages of selective permeable membrane- The useful molecules enter the cell, Secretion and waste leave the cell. Thus, the selective permeable membrane enables the cell to maintain homeostasis, i.e. a constant internal environment inspite of changes outside it.

Plasma membrane also perform some Activities, such as- Diffusion, Osmosis

(a).Diffusion = some substances such as CO2, O2, Water, etc., can move across the Plasma membrane through a Process called Diffusion. It can occur in any medium and the diffusing molecules may be solid , liquid and Gases. An equilibrium in the free energy of diffusion molecules is achieved in the system.

(b).Osmosis = The spontaneous movement of water molecules through a selective permeable membrane is called Osmosis. It occurs only in Liquid medium and involves movement of solvent moecules only. Equilibrium in Free energy of solvent molecules is never achieved.

2). Nucleus –

Generally The central Part of The cell is known as Nucleus. The Nucleus is a large, Centrally Located spherical cellular component. Nucleus is bounded by two nuclear membranes, both forming a nuclear envelope. Nuclear envelope separates the nucleus from the cytoplasm. The Nuclear envelope contains many pores and enclose the liquid ground materials known as nucleoplasm and that small pores is called nucleopores. These Nucleopores allow to transfer of materials between the nucleoplasm and the cytoplasm.

In Nucleoplasm, two types of nuclear structures are embedded i.e. NUCLEOLUS & CHROMATIN MATERIALS. nucleolus are Rich in Protein and also known as factory of Ribosomes.  Ribosomes helps n protein synthesis in the cytoplasm.

3). Cytoplasm –

Cytoplasm is one of the most important part of cell that occurs between the plasma membrane and nuclear membrane. Generally Cytoplasm is a Jely like structure present in cell contains cell organelles such as ribosome, chromosome, Lysosome, and golgi complex, etc.

The inner mass of cytoplasm is often called endoplasm while the outer layer is called ectoplasm. Cytoplasm consists of an aqueous materials called cytosol. Cytosol acts as a sore of vital chemicals such as Amino Acids, Glucose, Vitamins, ions, etc.

Chromosome and Its Structure

DNA molecules in our body

Chromosomes are the Thread like structures usually present in the nucleus that become visible only during cell divisions that is meiosis and mitosis. Chromosomes contain Genetic as well as heredity information of the cell in form of genes.

Each Chromosome is made up of mainly two components-

  1. DNA.
  2. Proteins.

1). DNA = DNA stands as deoxyribonucleic acid. It is the most important component of chromosomes and plays a vital role in born of new baby.

2). Proteins = Proteins are the large bio molecules that consists of one or more long chains of amino acid such as glutamine.

Structure of Chromosome-

Chromosome structure

Chromosomes consists of two arms that extend out from a specialized region of DNA called as centromere which means the middle body. Centromere helps to give a particular shape of chromosome. The Chromosome terminal regions on either side are called as Telomere. Each DNA molecule of each chromosome makes a copy of itself and become associated with proteins. The two copies of chromosomes remain attached at their centromeres. As long as Two copies of a chromosome are attached to a common centromere they are called sister chromatids.

Diploid and Haploid Number of chromosome-

Every Eukaryotic species has a fixed number of chromosome in their cell but some species have vary in number of chromosomes. Such as human Beings contain 46 number of chromosomes in each body cell (in which 44 chromosomes are Autosomes but 2 are sex chromosomes).

There is always a pair of chromosome number of each kind and the paired condition is known as DIPLOID and the cells that contains diploid chromosomes are called as diploid cell. And a set of unpaired chromosomes of each kind of cell is known as Haploid and that cell which contains haploid chromosome are known as haploid cell.

Cytoplasm

Introduction-

Cytoplasm is one of the most important part of cell that occurs between the plasma membrane and nuclear membrane. Generally Cytoplasm is a Jely like structure present in cell contains cell organelles such as ribosome, chromosome, Lysosome, and golgi complex, etc.

The inner mass of cytoplasm is often called endoplasm while the outer layer is called ectoplasm. Cytoplasm consists of an aqueous materials called cytosol. Cytosol acts as a sore of vital chemicals such as Amino Acids, Glucose, Vitamins, ions, etc.

Cytosol-

Cytosol is the soluble part of cytoplasm. It forms the Background Materials of the cytoplasm and is located between cell organelles. It contains a system of protien fibres called cytoskeleton. cytoskeleton contains three types of Protein Fibres-

  1. Tubulin Proteins,
  2. Actin proteins,
  3. Keratin and other types of protein.

These Fibrous Proteins help in cellular movement in organism’s Body and also helps to maintain their shape.

Chemicals constituents of cytosol-

CHEMICALSPERCENTAGE
1.oxygen64
2.carbon18
3.Hydrogen10
4.Nitrogen0.3

Cell Organelles-

A cell performs various types of functions with the help of different cell Organelles that it contains. cell organelles are the small organs of the cell that are found embeded in a cytoplasm. Some Properties of cell organelles are following-

  • It secrete the cell products such as enzymes, hormones and mucus, etc.
  • It generates Energy.
  • It digest those substances which are taken up by the cell during Endocytosis.

Some important cell organelles are- Ribosome, Golgi Apparatus, Lysosomes, Mitochondria, Chloroplast and centrosome, etc.

 

See Also


 

 

 

 

 

 

 

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It is Arpan Priy Das from west champaran, Bihar. Arpan started his blog about agricultural information named as “ECOHILLAGRI.COM ” He started his blog ecohillagri.com to help many agricultural or other students as well as farmers. so, it is necessary for them to learn about agriculture that is useful for students as well as farmers and that all concepts are present in this blog.

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