BASIC STRUCTURE OF A CELL
Though the cell very greatly in their size and shape, but all of these have a similar basic structure and perform similar basic functions like respiration, etc. in a similar manner.
So cell is rightly called the fundamental, structural and functional unit of life.
THREE FUNCTIONAL REGIONS OF A CELL
1) Plasma Membrane
2 2) Cytoplasm
3) Nucleus
Cytoplasm and nucleus collectively from the protoplasm. In plant cells, cell membrane is externally covered by a cell wall.
1 1) PLASMA MEMBRANE (CELL MEMBRANE)
Position :-
Outermost, thin, transparent, elastic, porous, regenerative and electron microscopic covering of cell.
Structure :-
Lipoproteinous (Lipid and Proteins) and trilaminar (3-layered).
Function :-
·Acts as semipermeable membrane and regulates exchange of materials between cytoplasm and extra cellular medium.
·Protects various cytoplasmic structures.
·Provide definite shape.
22) CYTOPLASM
Position :-
A colloidal and viscous ground substance present between the plasma membrane and nucleus.
Structure and Function:-
Ground substance is called matrix which has a number of living structure, called cell organelles, each for specific function.
I. Cell Organelles (Living Structure)
a. Mitochondria
·Act as “Power houses” of cell and seat of cell respiration and energy (ATP) formation.
b. Ribosomes
·Sites of protein synthesis so called protein factories.
c. Endoplasmic Reticulum
·Storage and Intracellular transport of materials.
d. Golgi Body
·Synthesis and secretion.
e. Lysosomes
·Intracellular digestion of food , germs, etc.
·Autodigestion after cellular death, so called suicidal bags.
f. Centrioles (Only in animal cells)
·Spindle formation and cell division.
g. Cilia and Flagella (Generally in animal cells)
·Movement and locomotion
h. Chloroplasts (Only in plant cells)
·Act as “kitchens” of the cell as are sites of photosynthesis.
II.
Cell
inclusions (Non-living structures)
a. Starch grains and Glycogen grain
·Starch is stored food of plants.
·Glycogen is stored food of animals.
b. Vacuoles (Generaly in Plant cell)
·Store the cell sap.
c. Urea, Uric acid etc.
·Metabolic wastes
3 3) NUCLEUS
Position :-
It is found in the centre of a cell.
Structure and Function:-
Generally there is single, centric, spherical or oval-shaped nucleus.
a. Nuclear membrane (2-layered porous envelope)
·Regulates exchange of materials between cytoplasm and nucleoplasm .
b. Nucleoplasm (Transparent and colloidal ground substance)
·Seat of RNA and DNA synthesis; help in cell division.
c. Nucleolus
·Formation of ribosomal-RNA
d. Nuclear Chromatin (A network of dark coloured chromatin fibres which condense and form chromosome during cell division)
·Carry genes which help in transmission of characters (heredity).
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