Phase Contrast Microscopy – Optical Components, Working Principle and Applications (Short Notes with PPT)


Applications of phase contrast microscope

Phase Contrast Microscopy
(Optical Components, Working Principle and Applications of Phase Contrast Microscope)

Working Principle of an Ordinary Microscope:

contrast in light microscopyIn an ordinary microscope, the object is viewed due to differences in colour intensities of the specimen. To create the colour intensities, the specimen is first stained with suitable dyes which will impart specific colour. In an ordinary microscope, the contrast is obtained when the light rays pass through a stained specimen because different stains absorb different amounts of light. These differential absorption properties of stained specimen modify the intensity or amplitude of the light waves transmitted by different regions of the cells and this ultimately creates contrast in the image. Thus, staining is essential to create contrast in an ordinary microscope. Moreover, the unstained specimen cannot be observed through an ordinary microscope.

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Why Phase Contrast Microscope?

The Phase Contrast Microscope is used to visualize unstained living cells. Most of the stains or staining procedures will kill the cells.  Phase contrast microscopy enables the visualization of living cells and life events.

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GATE life Sciences Study Materials

GATE XL 2018 Microbiology Solved Question Paper with Answer Key


GATE Microbiology Old Question Papers

Official / Original (Previous Year – Old) Solved Question Paper of GATE Life Sciences (XL) 2018 (Microbiology) with Answer Key and Explanations as PDF. GATE XL aspirants can download the question paper as single PDF file for your exam preparation. Please feel free to inform us for any mistakes in the answer key provided.

To download the question paper, please click on the download link below the preview…


GATE XL Model Questions GATE XL Previous Year Papers


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Immunoglobulins (Antibodies): Structure, Characteristics and Functions


Structure of Antibodies

Structure and Functions of Immunoglobulins (Antibodies)
The Organization of Heavy and Light Chains in an Immunoglobulin (Ig)

In the previous post, we have discussed the introductory features of antibodies. There we have also discussed the reason for calling Antibodies (Ab) as Immunoglobulins (Ig).  In this lesson, we will see the detailed molecular structure and organization of immunoglobulins (antibodies).

Immunoglobulin ShapeWhat are Immunoglobulins (Ig)?

As we discussed earlier, the Antibodies or Immunoglobulins are globular proteins present in the serum and tissue fluids. They are produced by the plasma cells (B-cells) and are used in the immune system of the body to neutralize pathogenic microbes or other toxic foreign components. Antibodies play a very crucial role in the immune system of an organism. Antibodies bind to definite molecules of microbes called antigens with high affinity and specificity. This enables our immune system to detect foreign organisms such as invading pathogens, of its products and initiate the mechanism to eliminate these foreign particles. The production of antibodies by the plasma cells is also stimulated by the antigens.  

How Immunoglobulins (Ig) are classified?

The immunoglobulins constitute about 20 – 25% of the total serum proteins. Based on the Physiochemical and Antigenic differences, the immunoglobulins are classified into FIVE categories. These immunoglobulins variants are called as Isotypes. The five isotypes or classes of the immunoglobulins are given below.

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Lecture notes in Microbiology

Difference between Bacterial Endotoxin and Exotoxin – Comparison Table


Compare Exotoxin and Endotoxin

Endotoxins vs Exotoxins
(Difference between Bacterial Endotoxin and Exotoxin)

Microbial toxins are noxious substances produced by the microorganisms such as bacteria and fungi in order to promote their pathogenicity and disease-causing process. The microbial toxins usually destroy the host tissue and they facilitate the infection by disabling the host immune system. A disease that results from a specific toxin is denoted as ‘Intoxication’. A toxin is a substance that alters the normal metabolism of host cells with deleterious effects. The term ‘Toxemia’ refers to the condition caused by the toxins that have entered the bloodstream of the host.

The toxins produced by bacteria are categorized into two main categories: (1) Endotoxins and (2) Exotoxins.

More in Microbiology: Lecture Notes, PPTs, MCQs

(1). Endotoxins: They are also called as Lipopolysaccharides or LPS. LPS are present on the outer membrane of the cell wall of Gram-negative bacteria that, under certain circumstances, become toxic to specific hosts. Lipopolysaccharides are called endotoxins because they are bound to the bacterium and they are released only when the bacterial cells lyse.

Lipopolysaccharides Toxin

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