Tools and Techniques in Biological Studies

The study of various aspects of life activities requires the use of certain techniques and analytical instruments. Physical and chemical sciences have helped scientists in developing some tools and techniques with the help of which biologists have been able to get a clearer insight into the life processes. Let us look into some of these tools and techniques.

Compound Microscope

It is the most widely used instrument in the field of biology. It is a device meant for magnifying biological objects that cannot be seen with the naked human eye. It has two sets of lenses - objective and ocular - that magnify an object in two steps. A compound microscope can give a magnification of more than 1000 times. (The resolving power of a compound microscope is 0.25 mm).

fig. 3.2- Compound Microscope

Electron Microscope

It is a sophisticated form of microscope, which can provide a higher magnification of the object (up to 1,00,000 times or more). The electron microscope employs an electron beam emanating from a cathode, instead of light as in the compound microscope. It uses coils instead of lenses.

fig. 3.3- Electron Microscope

There are two types of electron microscopes used in biological studies:

Transmission Electron Microscope (TEM)

It is used for the study of internal ultra structure of the cell organelles. It has a resolving power of 2 to 10⁰A.

fig. 3.4 - Transmission Electron Microscope

Scanning Electron Microscope (SEM)

It is used for the study of three-dimensional surface view of a given specimen. Its resolving power is also around 2 to 10⁰A.

fig. 3.5 - Scanning Electron Microscope

Homogenisation

It is a technique used for rupturing the cell walls and cell membranes for getting a suspension of cell components. It is done with the help of a homogeniser in which the plant or animal material is placed in a hypotonic solution.

fig. 3.6 - Homogeniser

Centrifugation

Centrifugation is a process by which, the homogenate or suspension of biological material is rotated in circle around a central axis at different speeds. The instrument used for this is called centrifuge. Due to the centrifugal force, the different components settle down in different layers, based on their mass.

fig. 3.7 - Centrifuge

Chromatography

It is a technique for separation of the components of a mixture by partitioning between two solvent systems. One of them is held immobile (stationary phase) and the other mobile (liquid phase).

fig. 3.8 - Chromatography

Chromatography is divided into five types depending on the nature of solid phase used. They are as follows:

Paper chromatography

Where cellulose filter paper is used as stationary phase.

Thin layer chromatography

Where a thin layer of cellulose or silica or gel is used.

Column chromatography

Where a solid absorbent such as charcoal powder is used.

Gas chromatography

Where a volatile substance is used as a stationary phase.

Ion-exchange chromatography

Where labile (unstable) ions are used as adsorbent.

Colorimetry

It is a technique used for measuring the density of a coloured substance in a solution. The instrument used is called colorimeter. Here, monochromatic filters are used and light rays of specific bands of wavelength are passed through the solution. Any compound present in the solution, reduces the intensity of the transmitted beam due to absorption and this can be recorded by a photocell.

fig. 3.9- Calorimeter

Freeze Etching

It is a technique in which cells and tissues are frozen and then cut with a microtome knife. This technique helps in studying cell surfaces and intracellular organelles.

Histochemistry

It is a technique in which specific stains are used for intracellular localisations of chemical substances. It is useful in studying the chemical components of cells in health and disease.

fig. 3.11 - Histochemistry