08 – Cell – Structure and Functions | Science | NCERT | Class 8

Here a student can find important notes in a listed form for quick revision and study. The blog includes the important definitions and terminologies from the Chapter : Cell Structure and Functions from NCERT Science, of Class 8.

  • Cell is the basic structural unit of an organ.
  • Robert Hooke in 1665 coined the term cell.
  • The yolk part in egg of a hen represents a single cell.
  • Organisms made of more than one cell are called multicellular organisms.
  • The single-celled organisms are called unicellular, example amoeba.
  • In case of amoeba, it has no definite shape, unlike other organisms. It keeps on changing its shape.
  • The projections of varying lengths protruding out of its body, called as pseudopodia.
  • A white blood cell (WBC) in human blood is another example of a single cell which can change its shape.
  • The nerve cell receives and transfers messages, thereby helping to control and coordinate the working of different parts of the body.
  • Bacterial cell has a cell wall.
  • The smallest cell is in bacteria & the largest cell measuring is the egg of an ostrich.
  • Nerve cells perform the function of transferring messages.
  • A tissue is a group of similar cells performing a specific function.
  • An organ is made up of tissues which in turn, are made up of cells.
  • The basic components of a cell are cell membrane, cytoplasm and nucleus.
  • The cell membrane separates cells from one another and also the cell from the surrounding medium.
  • The plasma membrane is porous and allows the movement of substances or materials both inward and outward.
  • Nucleus : The central dense round body in the centre is called the nucleus. It is an important component of the living cell. It is generally spherical and located in the centre of the cell.
  • Cytoplasm : It is the jelly-like substance between the nucleus and the cell membrane. It is present between the cell membrane and the nucleus.
  • Cell wall : In cells of plants, there is an outer thick layer in addition to the cell membrane, called the cell wall.
  • A cell wall is absent in animal cells.
  • Organelles : The various other components of cells present in the cytoplasm of a cell are called as organelles, like mitochondria, golgi bodies, ribosomes, etc.
  • Nuclear membrane : Nucleus is separated from the cytoplasm by a membrane called the nuclear membrane. It is porous and allows the movement of materials between the cytoplasm and the inside of the nucleus.
  • Nucleolus : A smaller spherical body in the nucleus, called the nucleolus.
  • Chromosomes : Nucleus contains thread-like structures called chromosomes. The chromosomes can be seen only when the cell divides.
  • Chromosomes carry genes and help in inheritance or transfer of characters from the parents to the offspring.
  • Gene is a unit of inheritance in living organisms. It controls the transfer of a hereditary characteristic from parents to offspring.
  • Nucleus, in addition to its role in inheritance, acts as control centre of the activities of the cell.
  • Protoplasm : The entire content of a living cell is known as protoplasm. It includes the cytoplasm and the nucleus. Protoplasm is called the living substance of the cell.
  • There is no nuclear membrane in bacterial cell.
  • Prokaryotic cells : The cells having nuclear material without nuclear membrane are termed prokaryotic cells, and the organisms called as prokaryotes. Examples: Bacteria and blue green algae.
  • Eukaryotic cells : The cells having well-organised nucleus with a nuclear membrane are called as eukaryotic cells. Examples: all organisms other than bacteria and blue green algae.
  • Vacuole : The blank-looking structures in the cytoplasm are called vacuole. Vacuoles are larger in plant cell and smaller in animal cells.
  • Plastids : Several small coloured bodies scattered in the cytoplasm of leaf cells are called plastids. They are of different colours.
  • Chloroplasts : Green coloured plastids are called chloroplasts. They provide green colour to the leaves.

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10 Comments

  1. Wa wa ek chapter ke notes ek hi jagah pe mast,
    Pop kardiya bhai:-! πŸ˜πŸ‘“πŸ˜„πŸ˜„

  2. Thanks:-!
    Can you please send some more chapters of this
    Please,Request Sir:-! πŸ™πŸ˜’πŸ‘†

  3. Hello! Sir thanks for giving us these good notes! πŸ˜€πŸ˜€πŸ–•
    Sir can you send question and answers of all chapters these science.
    Thanks for support!

  4. Sir please send sir more chapters from 9 to 18
    Due to half of the year was already gone so I want them
    Sir if you able to send then please send sir we need them.πŸ‘ƒπŸ˜ŠπŸ˜Š

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