Exam Preparation Notes for Microscopy

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Final exam may include questions on previously unassessed topics like the Auchin glade.
A preparatory sheet for microscopy images will be compiled for the final exam.
- Students will be allowed to bring in handwritten notes on a separate piece of paper to assist in answering questions.
- Exam questions will focus on application and critical thinking rather than memorization of components.

Students are encouraged to take notes during class and compile information as they prepare for the microscopies.
The instructor will provide additional resources and demonstrations pertaining to Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM).

Structure: TEM uses a column structure that contains a cathode and anode for electron movement.
- Cathode: Emits electrons when heated.
- Anode: Positively charged and attracts electrons emitted from the cathode.
Vacuum Requirement: The entire system operates under a vacuum to prevent electron scattering by air.
Sample Preparation: Involves critical steps such as fixation, embedding, sectioning, and possibly staining.
- Fixatives typically used: Lunaraldehyde (primary) and Osmium Tetroxide (secondary).
- Specimens must be cut exceedingly thin (angstroms) for optimal observation.
Electromagnetic Lenses: Used instead of glass lenses to focus electrons, adjusting magnification and resolution through voltage control.
Observation and Imaging: After sectioning, images are produced on a phosphorescent screen, visible as light-emitting areas where electrons interact with the sample.
- Images are typically grayscale and exhibit structures at high magnification.

Samples usually require heavy metal staining for better visibility under high magnification.
The staining process can result in significant detail, crucial for studying cellular structures like mitochondria and membranes.

Overview: SEM focuses on external surfaces of samples instead of internal structures.
- Common samples: Insects, biological materials, and various materials for structural analysis.
Electron Gun & Samples: Similar mechanisms as TEM but with emphasis on surface imaging techniques.
Sample Preparation: Involves cleaning, fixing, and sometimes coating samples with gold or palladium to prevent charging during imaging.
Image Formation: When electrons hit the sample, they create backscattered or secondary electrons, which are collected to form an image.
Applications: SEM is versatile and can be paired with techniques like Elemental Dispersive X-ray Analysis (EDX) to determine material compositions.

Both TEM and SEM utilize electron beams for imaging but are designed for different observational purposes (internal vs. external structures).
TEM requires more complex sample preparation while SEM can be quicker due to external observation capabilities.
Each method has its unique advantages and applications, providing critical insights into microstructural characteristics in various fields of research, including biology, material science, and medicine.