Introduction of Cell Biology
Cells are tiny but complex bodies. It is difficult to see their structure; more difficult to understand their molecular composition and still difficult to find out the function of their various components.
What one can learn about cells, depends on the tools at one's disposal and, in fact, a major advances in cell biology have biology have frequently taken place with the introduction of new techniques to the study of cells.
Two types of techniques
1. First techniques of Microscopy
In the 1st technique for information about the structure and composition of cells, the cell biologist immediately face two limitations of Microscopy: the exceedingly small and little dimensions of cells and their components part and the transparent nature of the cells
2. The second technique of Light Microscopy
The 2nd technique compound light microscope uses visible light for illuminating the object and contains glass lenses that magnify the images of the objects and focus the light on the retina of the observer's eyes of the human. It consists of two lenses, one at each end of a hollow tube of light Microscopy. The lens closer to the eye is called the ocular lens or objective lens.
The Light microscopes are the following types that are:
1. The Darkfield microscope or Ultramicroscope
2. The Phase contrast microscope
3. The Polarization microscope
Methods of Sample for Light Microscopy
Cells are transparent of the human body and optically homogeneous: so either they are viewed as such by instruments such as a phase-contrast sample preparation microscope or to produce necessary contrast, the cells are passed through various steps of slide sample preparation such as killing, fixation, dehydration, embedding, sectioning, staining and mounting.
Electron Microscopy
The electron microscopy uses the much shorter wavelengths of electrons to achieve resolution as low as 3A degree, with a usual working range between 5 to 12 A degree.
Methods of Sample for Transmission Electron Microscopy
Transmission's methods of the standard procedure for the preparation of specimens for TEM entails fixation, dehydration, staining, and sectioning similar to light microscopy of Transmission Electron Microscopy. However, the most significant difference being the need for ultra-thin sections sample. The following techniques of the sample are generally used for different types of methods of studying the ultrastructure of the cell is:
1. Monolayer technique
2. Thin sectioning
3. Negative staining
4. Shadow casting
5. Tracers
6. Freeze- fracture
7. Whole mounts
The Analysis of X-Ray Diffraction
X-Ray Diffraction technique is used to analyze three- dimensional structure of DNA molecule and a variety of proteins such as myoglobin, hemoglobin, collagen, myelin sheath of nerve cells, myofibrils of striated muscles, etc. This method depends on the fact that the analysis of X-ray is scattered or diffracted by the atoms of a substance. If the material has an ordered crystalline atomic structure of cells, the resulting X-ray diffraction pattern is also ordered and reflects the three- dimensional arrangement of atoms in the crystal.
The Cell Fractionation
Cell Fractionation sometimes of cell biology it becomes necessary to break up tissues and cells and to isolate various parts of the cell biology for structural and biochemical analysis. For the cell fractionation purpose, the technique of the cell fractionation is employed for separation. The cell fractionation method involves in cell biology, essentially the homogenization and destruction of cell boundaries by different mechanical and chemical procedures fractionation, followed by the separation and filtered of cells solution of the subcellular fractions according to the mass of elements' surface, and specific gravity by centrifuges of cells.
Autoradiography
Autoradiography is a technique that is used to locate radioactive isotopes in cells, tissues, organs, and the whole organism of the living organism cells. A specimen is exposed to a solvent molecule that has been made radioactive by the incorporation of radioactive isotopes, such as tritium, carbon 14, phosphorous, and sulfur. The tagged of chemical elements molecules are often precursor molecules used by the cell in the synthesis of other needed of elements molecules. At intervals of sample preparation, samples are removed from the solution of cells in this case of smaller tissues. the samples are sectioned and mounted on glass slides and grids. The sections are then coated with a photographic emulsion and stored in the period ranging up to several months and years.
Cell culture
For the cell biological observations sometimes as well as every time it is needed to keep the animal and plant and cell in living state outside the organism under favorable conditions. This process is called cell culture. The cell biological cultures are mainly3 types: 1st is primary, 2nd is secondary, and those using established cell lines. Primary cultures are those obtained directly from animals and all living tissue. The organ is aseptically removed, cut into small fragments, and treated with trypsin enzymes to dissociate the cell aggregates into a suspension of viable single cells. These cells are plated in sterile Petri-dishes and grown in the appropriate culture medium of living organisms. When this culture is trypsinized and re-plated in a fresh medium then resultant culture is called a secondary culture of cells.
Chromatography
The chromatography is used to separate and the filters the molecules of different substances present together in a solution and cytosol. The cell solution is applied to an insoluble medium which has a different affinity for the individual molecules of the solution so that the molecules migrate through the medium as well as high at different rates.
Dialysis
Dialysis is a sensitive method for separating lower molecular -weight components from macromolecules. Cells are a thin membrane in the form of a dialysis tube is filled with the cells solution containing the solvent molecules to be separated from cells. The pore size of the membrane allows the diffusion of small molecules such as salt and amino acids; larger molecules such as proteins and nucleic acids cannot pass through the pores and so remain inside the dialysis tube.