Definition of Cell and components of cell

Cell :

Structrual and functional unit of living of living organism is called cell.

Cytology : 

The branch of science which deals with the study of cells are known as cytology.

Types of cell in human body :

Cartilage cells : In human body it is mainly found in the joints, between the two ribs, ear and spinal bones.
Nerve cells : Generally Nerve cells are present in spinal cord and brain.
Epithelial cell :  Present in skin, scalp, respiratory tract, in the bucal cavity surface over the surface of heart etc.
Muscle cells :  Skeletal, cardiac and smooth muscle cells.
Secretory cells :  Pancreatic cell which secretic insulin, glucagon, salivary gland secrete salivary amylase, sebacious gland secrete oil on the skin .
Adipose cell :  These are fat cell and are sites where fat are stored. They are mainly see in the soles, palms, bums etc.
Blood cell :  These cell include RBC, WBC and Thermocytes etc.
Special types :  Sperms, stem cells, rods and cones, ciliated cell, blood cell, pancreatic cell etc.

Component of cell :

(A)  Plasma membrane
(B)  Nucleus
(C)   Cytoplasm
Cell, cytology, human cell, endoplasmic reticulem, nucleus, Lysomes, mitochondria


(A)  Plasma membrane :

-  It is a semipermeable membrane.
-  It is made up with lipid,protein,and small amount of carbohydrate.
-  It communicate between two cell.
-  It separate the cell from internal and external environment.
-  It protect the cell.

Function  :

-  It helps for cell recognization.
-  It helps for impulse transmission.
-  It gives a perfect shape and size to the cell.

(B) Nucleus  :

-  It consists of nucleoplasm,nucleoli and chromosome.
-  It helps for protein synthesis and cell division.

(C) Cytoplasm  :

-  It present between the plasma membrane and nucleus .
-  It is viscous and translucent . It is a jelly like substance.
-  Organells are suspended in cyyoplasm as it is a jelly like substance.

The following organells are present in cytoplasm :

(1)  Endoplasmic reticulum
(2)  Golgi apparatus
(3)  Mitochondria
(4)  Microtubules
(5)  Microcomputer
(6)  Lysomes

(1)  Endoplasmic reticulum :

-  Network of interconnected tubes are present.
-  It is bounded by lipid bilayer which is made up of proteins.

Types :

-  Smooth endoplasmic reticulum , it concern for lipid synthesis.
-  Rough endoplasmic reticulum , it concern for protein synthesis.

(2) Golgi apparatus :

-  4-5 layers of flat vessels are present in it.
-  It secretes enzymes and hormones.
-  It produces lysome from endoplasmic reticulum.

(3) Lysome :

-  Lysome is made up of lipid bilayer.
-  It kills the toxic substance.
-  Lysozyme and lysoferin are bactericidal in nature.

(4) Mitochondria :

-  It is known as power house of the cell.
-  It is made up of lipid bilayer but inner layer is folded to produce more number of ATP.
-  Mitochondria also contain DNA . Which can produce more number of mitochondria.

(5) Peroxisomes :

-  It is 250 to 750 nanometers.
-  It is bounded by lipid bilayer.
-  It contain oxidase .
-  Formed by budding off from smooth ER.

(6) Microfilament and microtubules :

It acts as cytoskeleton providing rigid physical structure for certain parts of cell.
E.g..  Actin in ectoplasm,  microtubules in cilium,  centriole and mitotic spindle.

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