12-12-2011, 02:10 AM
(This post was last modified: 12-12-2011, 04:18 AM by Administrator.)
Modern cytology is named as cell biology. Cell biology approaches the problems of the cell at different levels of organization from molecular level onwards. It forms a common level of convergence of genetics, physiology and biochemistry. Cytology was primarily concerned with the morphology of cell.
A cell is the smallest but complete expression of the fundamental structure and function of all living organisms, which is capable of independent existence and self reproduction in a suitable non living medium. It has the following characteristics:
1. A cell membrane that establishes a boundary regulating all exchanges of matter and energy.
2. A metabolic machinery that can use the energy trapped by the cell or obtained from food stuffs. (Mitochondria)
3. A biosynthetic machinery for the synthesis of protein (RNA and ribosome.)
4. A specific genetic programme in the nucleus that permits the reproduction of the new cells of the same type.
Within cells there is an complicated network of organelles that all have unique functions. These organelles are assigned to perform different functions. The morphology of the cell can be studied under three locations such as surface, cytoplasm and nucleus.
The surface of the cell includes cell wall and plasma membrane or they are also called as cell membrane system.
Cell wall is most commonly found in plant cells which are thick, rigid, non living and formed of cellulose .They are Extracellular structure surrounding plasma membrane ,Whose main function is to protect the cell and control turgity. Cell wall is classified as primary and Secondary cell wall. Primary cell wall is extremely elastic and Secondary cell wall are formed around primary cell wall after growth is complete.
Plasma membrane is the Outer membrane of cell that controls cellular traffic. They are formed of lipid bilayer sandwiched between two protein layers. They perform the function of regulating materials in and out of cell. They help in the maintenance of the cell shape and cell communication.
Cytoplasm or the cytosol is the protoplasm of the cell surrounding the nucleus and enclosed in the plasma membrane. Contains organelles in the Colloidal suspension which may include Centrioles, Chloroplasts, Cytoskeleton, Endoplasmic reticulum, Golgi apparatus, Lysosome, Mitochondria, Ribosomes, and Vacuoles.
Centrioles
They are composed of nine tubes, each with three tubules which occur in the form of pairs in cylindrical shapes near the nucleus. They are actively involved in cell division and are placed at right angles to each other.
Chloroplasts
These are the plastid usually found only in plant cells. They contain green chlorophyll where photosynthesis takes place.
Cytoskeleton
They are composed of microtubules and supports the cell and also provide shape to the cell. They help in the endocytosis and exocytosis of the cell.
Endoplasmic reticulum
They consists of tubular network fused to nuclear membrane which goes through cytoplasm onto cell membrane. They are differentiated into two forms called Smooth Endoplasmic reticulum and Rough Endoplasmic reticulum. The former lacks ribosomes and the later contains ribosomes embedded in surface. These perform the function of storing, separating, and serves as cell's transport system.
Golgi apparatus
This is a membrane structure found near nucleus Composed of numerous layers forming a sac. They are also termed as Protein 'packaging plant' as they perform this function.
Lysosome
These organelles Vary in shape depending on process being carried out. They Transport undigested substances to cell membrane for elimination. Cell breaks down if lysosome explodes.
Mitochondria
Are often termed as the power house of the cell and are the Second largest organelle with unique genetic structure. They are Double-layered outer membrane with inner folds called cristae. Energy-producing chemical reactions take place on cristae.Its function includes recycling and decomposing proteins, fats, and carbohydrates, and forms urea. They Control the level of water and other materials in cell.
Ribosomes Composes 25% of cell's mass. They are small 'protein factories' present in the cell in thousands. They are present in two forms like Stationary and Mobile type. Stationary ones are embedded in rough endoplasmic reticulum and mobile ribosomes injects proteins directly into cytoplasm.
Vacuoles are Membrane-bound sacs for storage, digestion, and waste removal, which contains water solution, helps in water removal in unicellular organisms.
Lastly the cell contains nucleus. They can be one or more per cell and are Spherical in shape. They are dense in from than the surrounding cytoplasm. They consist of Chromosomes, Nuclear membrane, Nucleolus.
A cell is the smallest but complete expression of the fundamental structure and function of all living organisms, which is capable of independent existence and self reproduction in a suitable non living medium. It has the following characteristics:
1. A cell membrane that establishes a boundary regulating all exchanges of matter and energy.
2. A metabolic machinery that can use the energy trapped by the cell or obtained from food stuffs. (Mitochondria)
3. A biosynthetic machinery for the synthesis of protein (RNA and ribosome.)
4. A specific genetic programme in the nucleus that permits the reproduction of the new cells of the same type.
Within cells there is an complicated network of organelles that all have unique functions. These organelles are assigned to perform different functions. The morphology of the cell can be studied under three locations such as surface, cytoplasm and nucleus.
The surface of the cell includes cell wall and plasma membrane or they are also called as cell membrane system.
Cell wall is most commonly found in plant cells which are thick, rigid, non living and formed of cellulose .They are Extracellular structure surrounding plasma membrane ,Whose main function is to protect the cell and control turgity. Cell wall is classified as primary and Secondary cell wall. Primary cell wall is extremely elastic and Secondary cell wall are formed around primary cell wall after growth is complete.
Plasma membrane is the Outer membrane of cell that controls cellular traffic. They are formed of lipid bilayer sandwiched between two protein layers. They perform the function of regulating materials in and out of cell. They help in the maintenance of the cell shape and cell communication.
Cytoplasm or the cytosol is the protoplasm of the cell surrounding the nucleus and enclosed in the plasma membrane. Contains organelles in the Colloidal suspension which may include Centrioles, Chloroplasts, Cytoskeleton, Endoplasmic reticulum, Golgi apparatus, Lysosome, Mitochondria, Ribosomes, and Vacuoles.
Centrioles
They are composed of nine tubes, each with three tubules which occur in the form of pairs in cylindrical shapes near the nucleus. They are actively involved in cell division and are placed at right angles to each other.
Chloroplasts
These are the plastid usually found only in plant cells. They contain green chlorophyll where photosynthesis takes place.
Cytoskeleton
They are composed of microtubules and supports the cell and also provide shape to the cell. They help in the endocytosis and exocytosis of the cell.
Endoplasmic reticulum
They consists of tubular network fused to nuclear membrane which goes through cytoplasm onto cell membrane. They are differentiated into two forms called Smooth Endoplasmic reticulum and Rough Endoplasmic reticulum. The former lacks ribosomes and the later contains ribosomes embedded in surface. These perform the function of storing, separating, and serves as cell's transport system.
Golgi apparatus
This is a membrane structure found near nucleus Composed of numerous layers forming a sac. They are also termed as Protein 'packaging plant' as they perform this function.
Lysosome
These organelles Vary in shape depending on process being carried out. They Transport undigested substances to cell membrane for elimination. Cell breaks down if lysosome explodes.
Mitochondria
Are often termed as the power house of the cell and are the Second largest organelle with unique genetic structure. They are Double-layered outer membrane with inner folds called cristae. Energy-producing chemical reactions take place on cristae.Its function includes recycling and decomposing proteins, fats, and carbohydrates, and forms urea. They Control the level of water and other materials in cell.
Ribosomes Composes 25% of cell's mass. They are small 'protein factories' present in the cell in thousands. They are present in two forms like Stationary and Mobile type. Stationary ones are embedded in rough endoplasmic reticulum and mobile ribosomes injects proteins directly into cytoplasm.
Vacuoles are Membrane-bound sacs for storage, digestion, and waste removal, which contains water solution, helps in water removal in unicellular organisms.
Lastly the cell contains nucleus. They can be one or more per cell and are Spherical in shape. They are dense in from than the surrounding cytoplasm. They consist of Chromosomes, Nuclear membrane, Nucleolus.
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