Differentiate between SEM and TEM. (IFS 2022/10 Marks)
Differentiate between SEM and TEM. (IFS 2022/10 Marks)
Introduction
Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) are two powerful techniques used in the field of zoology for studying the ultrastructure of biological samples.
Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM)
| Aspect | Scanning Electron Microscopy (SEM) | Transmission Electron Microscopy (TEM) |
|---|---|---|
| Principle | Uses a focused beam of electrons to scan the surface of a specimen. Produces 3D images by detecting secondary electrons emitted from the surface. |
Electrons are transmitted through a thin specimen. Produces 2D images based on electron density variations. |
| Sample Preparation | Samples are usually coated with a thin layer of conductive material. Specimens can be bulkier and less processed. |
Requires ultra-thin sections (around 100 nanometers). Often involves extensive sample preparation, including fixation and embedding. |
| Resolution | Typically lower resolution (about 1-10 nanometers). Adequate for observing surface structures and morphology. |
Higher resolution (up to 0.1 nanometers). Suitable for observing fine cellular structures and organelles. |
| Image Output | Produces three-dimensional images of the surface topology. Excellent for visualizing surface details of specimens. |
Produces two-dimensional images with high detail. Allows for internal structural analysis, such as organelle positioning. |
| Applications | Commonly used to examine surface structures of cells, tissues, and organisms. Useful in zoology for studying external features like scales, feathers, and surfaces of specimens. |
Ideal for studying internal cellular structures, such as membranes, organelles, and molecular complexes. Important for understanding cell ultrastructure in zoological studies. |
| Limitations | Cannot provide information about internal structures. Depth of field is limited; fine details may be less distinct. |
Time-consuming sample preparation can limit throughput. Can introduce artifacts due to the required sectioning. |
Conclusion
SEM and TEM are both valuable tools in zoology for studying the ultrastructure of biological samples. While SEM is ideal for surface imaging and three-dimensional visualization, TEM is better suited for studying the internal structure of cells and organelles at higher resolutions.