MCB 11 Microscopy Handout PDF

MCB 11 Lecture Section ST 1st Sem., 2024 – 2025 Handout #1 Microscopy Microscopy: Definition and Importance Microscopy is the science of using microscopes to observe objects and areas of objects that cann...

MCB 11 Lecture Section ST 1st Sem., 2024 – 2025 Handout #1 Microscopy Microscopy: Definition and Importance Microscopy is the science of using microscopes to observe objects and areas of objects that cannot be seen with the naked eye. This technique is fundamental in fields such as biology, materials science, and nanotechnology, allowing researchers to examine the structure, morphology, and function of cells, tissues, microorganisms, and materials in great detail. Importance of Microscopy: 1. Scientific Research: Essential for studying cells, microorganisms, and materials at a microscopic level. 2. Medical Diagnosis: Used in diagnosing diseases, analyzing blood samples, and identifying pathogens. 3. Educational Tool: Helps students learn about the microscopic world, such as cell structure and function. Types of Microscopes and Their Functions 1. Light Microscopes Light microscopes use visible light and optical lenses to magnify specimens. Key types include: Bright-field Microscope: o Function: Light passes directly through the specimen, suitable for observing stained or naturally pigmented samples. o Application: Cell morphology, tissue sections, microorganisms. Dark-field Microscope: o Function: Scatters light off the specimen, making it appear bright against a dark background. o Application: Observing live, unstained specimens like bacteria.  Phase-contrast Microscope: o Function: Enhances contrast in transparent specimens by exploiting differences in refractive index. o Application: Viewing live cells, cellular organelles, and unstained tissues. Fluorescence Microscope: o Function: Uses high-intensity light to excite fluorophores, emitting light at different wavelengths. o Application: Studying the localization of proteins, nucleic acids, and other cell molecules. Confocal Laser Scanning Microscope: o Function: Uses laser light to scan specimens, creating high-resolution 3D images. o Application: Detailed imaging of cells, tissues, and complex structures. 2. Electron Microscopes Electron microscopes use electron beams instead of light, providing much higher resolution. Types include: Transmission Electron Microscope (TEM): o Function: Electrons pass through a thin specimen, creating detailed images of internal structures. o Application: Studying the ultrastructure of cells, viruses, and protein complexes. Scanning Electron Microscope (SEM): o Function: Electrons scan the specimen's surface, producing 3D images of surface morphology. o Application: Examining the surface structures of cells, tissues, and materials. Scanning Transmission Electron Microscope (STEM): o Function: Combines aspects of both SEM and TEM, allowing for high- resolution study of both surface and internal structures. o Application: Nanomaterials, interfaces in materials, cellular structures. 3. Scanning Probe Microscopes Scanning probe microscopy involves scanning a probe close to a specimen’s surface to measure various properties, offering atomic or molecular resolution.  Atomic Force Microscope (AFM): o Function: A cantilever with a sharp tip scans the surface, measuring forces to create a topographical map. o Application: Surface roughness, nanostructures, biological specimens. Scanning Tunneling Microscope (STM): o Function: Measures tunneling current between a conductive tip and surface, providing atomic-level images. o Application: Atomic structure of conductive materials, surface defects. o Application: Optical imaging at a resolution beyond the diffraction limit. 4. Two-Photon Microscope Two-photon microscopy is a fluorescence imaging technique that uses two photons of lower energy (near-infrared) to excite fluorophores, allowing for deep-tissue imaging with reduced phototoxicity. Function: Excites fluorophores using two photons, allowing for deep tissue imaging with localized excitation. Application: Neuroscience (live brain tissue imaging), developmental biology, cancer research.