22. Techniques in Cell Biology

Electron Microscopy

22. Techniques in Cell Biology

Electron Microscopy: Videos & Practice Problems

Topic summary

Electron microscopy utilizes electrons for cell visualization, achieving a resolution of up to 0.002 nanometers, significantly surpassing light microscopy. Key techniques include immuno gold staining, which labels proteins with electron-dense gold, and metal shadowing, creating 3D structural images. The two main types are transmission electron microscopy (TEM), which transmits electrons through samples, and scanning electron microscopy (SEM), which focuses on surface details. These methods enable detailed observation of cellular structures, such as mitochondria, enhancing our understanding of cellular biology.

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Electron Microscopy

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Electron Microscopy Video Summary

Electron microscopy is a powerful imaging technique that utilizes electrons to visualize cells, offering a significantly higher limit of resolution compared to light microscopy. The theoretical resolution of electron microscopy can reach up to 0.002 nanometers, which is approximately 100,000 times greater than that of light microscopy. However, in practical applications, achieving this level of resolution is challenging due to various factors, including sample preparation and technique nuances.

To effectively use electron microscopy, samples must be meticulously processed. This involves preserving specimens and cutting them to an extremely thin thickness, typically 1 to 200 times thinner than a cell. Proper sample preparation is crucial because electrons require specific conditions to visualize the samples accurately.

One common method for preparing samples is immuno gold staining, which involves labeling specimens with a thin layer of gold. Gold is chosen for its electron density, allowing areas where it is applied to appear black under the electron microscope. This technique is particularly useful for identifying specific proteins or organelles within the sample.

Another preparation method is metal shadowing, where a specimen is coated with metal at a specific angle. This technique creates a shadowing effect, similar to spray painting a jagged rock, where some areas receive more coating than others. This results in a three-dimensional appearance that enhances the visualization of the specimen's structure.

There are two primary types of electron microscopy: transmission electron microscopy (TEM) and scanning electron microscopy (SEM). TEM involves shooting electrons directly through the sample, akin to how light is passed through a light microscope. In contrast, SEM scans the surface of the specimen with electrons, providing detailed images of surface structures. This difference in approach allows SEM to capture finer details of the specimen's exterior.

For example, electron microscopy can reveal intricate internal structures of organelles, such as mitochondria, showcasing features like the double membrane. The advancements in electron microscopy technology continue to improve the quality of images, enabling researchers to observe cellular components with remarkable clarity and detail, far surpassing the capabilities of light microscopy.

Problem

Light microscopy has an improved limit of resolution compared to electron microscopy.

True

False

Problem

Which of the following types of microscopy works by shooting electrons through the specimen?

Light microscopy

Transmission electron microscopy

Scanning electron microscopy

FRAP floruences microscopy

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Here’s what students ask on this topic:

What is electron microscopy and how does it differ from light microscopy?

Electron microscopy uses electrons to visualize cells, achieving a much higher resolution of up to 0.002 nanometers compared to light microscopy. This allows for much finer details to be observed. Light microscopy uses visible light to illuminate samples, while electron microscopy uses a beam of electrons. The higher resolution in electron microscopy is due to the shorter wavelength of electrons compared to light. However, electron microscopy requires more complex sample preparation, including preservation and ultra-thin sectioning, whereas light microscopy is simpler and can be used on live cells.

What are the main types of electron microscopy?

The two main types of electron microscopy are Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). TEM works by transmitting electrons through a thin sample, similar to how light passes through a sample in light microscopy. This method provides detailed images of the internal structure of cells. SEM, on the other hand, scans the surface of a sample with a focused beam of electrons, producing detailed 3D images of the sample's surface. Both techniques offer high-resolution images but are used for different types of structural analysis.

What is immuno gold staining in electron microscopy?

Immuno gold staining is a technique used in electron microscopy to label specific proteins or structures within a cell. This method involves coating the sample with a thin layer of gold, which is electron-dense. When electrons are directed at the sample, the gold-labeled areas appear as black spots in the resulting image. This allows for precise localization of specific proteins or organelles within the cell. The gold particles are often attached to antibodies that specifically bind to the target molecules, making this technique highly specific and useful for detailed cellular studies.

How does metal shadowing work in electron microscopy?

Metal shadowing is a technique used in electron microscopy to create a 3D effect by coating the sample with a thin layer of metal from a single angle. This process results in areas of the sample being more or less coated, creating shadows that highlight the surface contours and structures. Imagine spray-painting a jagged rock; the paint would be thicker in some areas and thinner in others, creating a shadow effect. This technique helps in visualizing the surface topology of the sample, providing detailed structural information that is useful for understanding the morphology of cellular components.

What are the advantages of using electron microscopy over light microscopy?

Electron microscopy offers several advantages over light microscopy, primarily due to its higher resolution, which can reach up to 0.002 nanometers. This allows for the visualization of much finer details within cells, such as the internal structures of organelles like mitochondria. Additionally, electron microscopy can provide detailed 3D images of the sample surface through techniques like scanning electron microscopy (SEM). However, these advantages come with the need for more complex sample preparation, including preservation and ultra-thin sectioning, which is not required for light microscopy. Despite these challenges, the enhanced resolution and detail make electron microscopy invaluable for advanced cellular studies.

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