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Cell-important-theory Biology-day-9 Target-ssc-cgl-2018

Cell-important-theory Biology-day-9 Target-ssc-cgl-2018

Cell-important-theory Biology-day-9 Target-ssc-cgl-2018

CELL  :  STRUCTURE AND FUNCTION

 In 1665, Robert Hooke discovered cells.

Cells are the basic unit of life. All the living organisms are made up of cells. Just like a house is made up of bricks.

A cell is the smallest unit of life and has definite structure. Also, it performs a specific function.

 

PARTS OF A CELL

  • The important basic parts which are present in all cells are …..  Cell membrane, Cytoplasm, Nucleus and Mitochondria.
  • Cell wall, Chloroplast and Large vacuoles are only present in the plant cell.

Cell membrane

  • Cell membrane is a thin sheet of skin which covers the cell.
  • It protects the cell and give it a shape.
  • It controls the movement of substances into and out of the cell.

Cytoplasm

  • A jelly-like substance which is present in the cell and fills the space between the nucleus and the cell wall.
  • Reactions which keeps the cell alive takes place here.
  • Cytoplasm contains various cell organelles.
  • Cytoplasm of plant cell contains chloroplast.

Nucleus

  • Nucleus is the largest cell organelle present in the cell.
  • In animal cell, nucleus lies in the centre of the cell while in the plant cell nucleus may lie on the periphery of the cell.
  • Nuclear membrane separates nucleus from cytoplasm.
  • Chromosomes are present in the nucleus. Chromosomes are responsible for the transfer of characteristics from parent to offsprings.

Cell wall

  • Cell wall is present around the cell membrane.
  • Cell wall is not present in the animal cells.
  • Cell wall is present in plant cell, but it is not living.

Mitochondria

  • Mitochondria provides energy (which it makes from glucose and oxygen) for all the activities of the cell.
  • Respiration is carried out in mitochondria.
  • Mitochondria make energy rich compounds adenosine triphosphate (ATP). It is therefore called the ‘powerhouse of the cell.’

Cell-important-theory
Ribosomes

  • Ribosomes are attached to the endoplasmic reticulum.
  • Ribosomes are made of ribonucleic acid (RNA) and proteins.
  • Ribosomes help in the synthesis of proteins.

Golgi Apparatus

  • It packs and dispatches materials that are synthesised in the cells.
  • It produces vacuoles.

Lysosomes

  • These are made by rough endoplasmic reticulum.
  • Lysosomes are called the digestive bags of the cell because they serve as intracellular digestive system.
  • Lysosomes also digest worn out cell organelles.
  • When the cell gets damaged, lysosomes burst and digest their own cell. Thus, they are called the suicide bags of the cells.

Chloroplast

  • It is the green colored organelle present in the plant cell.
  • Photosynthesis takes place in chloroplast.
  • Chloroplast is green in colour due to the presence of chlorophyll.
  • Chloroplast is a plastid. Plastids are those cell organelles which contains coloured pigment.

Vacuoles

  • It is a space in the cytoplasm and contains cell sap (salts and sugars dissolved in water).
  • Animal cells either do not have vacuoles or have very small vacuoles.

 

PROKARYOTIC CELLS

  • In prokaryotic cells, nuclear membrane is not present. Animals which have prokaryotic cells are called prokaryotes.
  • Example : Bacteria and blue-green algae.


EUKARYOTIC CELLS

  • In eukaryotic cells, nuclear membrane is present. Animals which have eukaryotic cells are called eukaryotes.
  • Eukaryotic cells have a proper and well organised nucleus.
  • Example : Amoeba, fungi and protozoa.

Cell-important-theory
 

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