Naomi Kinjal Asaad Binoy MICROSCOPES Naomi Kinjal Asaad Binoy

Microscopy Magnification is the ratio of an object’s image size to the real size Resolution is a measure of the clarity of the image; it is the minimum distance two points can be separated and still distinguished as two points

Different Types of Microscopes Light-visible- light is passed through the specimen and then through a glass lens. Specimen can be living or not; stained. Resolving power is limited by the wavelength of visible light. Electron-focuses a beam of electrons through the specimen or onto it’s surface; helps see cell organelles but not living specimen. Resolving power is larger since wavelengths of electrons are smaller than light

Electron Microscopy Techniques Scanning electron microscopy (SEM)-micrographs taken with a scanning electron microscope show a 3-D image of the surface of a specimen. useful for the detailed study of the surface of the specimen Transmission electron microscopy (TEM)-a transmission electron microscope profiles a thin section of a specimen. used to study the internal ultrastructure of cells

Light Microscopy Techniques Brightfield (unstained specimen)-passes light directly through specimen Brightfield (stained specimen)-staining with various dyes enhances contrast Phase-contrast-enhances contrast in unstained cells by amplifying variations in density within specimens Differential-interference-contrast (Nomarski)-uses optical modifications to exaggerate differences in density Fluorescence-shows the locations of specific molecules in the cell by tagging the molecules with fluorescent dyes or antibodies Confocal-a technique that uses a pinhole aperture to eliminate out-of-focus light from a thick sample

Uses for Microscopes Tissue Analysis-common for studying cells and tissues Studying the Role of a Protein within a Cell-helps study proteins in live cells Studying Atomic Structures-helps study the surfaces of individual atoms

Facts Cell walls were first seen by Robert Hooke in 1665 as he looked through a light microscope at dead cells from the bark of an oak tree It took Antoni van Leeuwenhoek's crafted lenses to help visualize living cells Cell biology advanced rapidly in the 1950s with the introduction of electron microscope Most cells are between 1 and 100 micrometers in diameter and are therefore visible only under a microscope Microscopes are the most important tools of cytology, the study of cell structure Modern cell biology developed from an integration of cytology with biochemistry

Limitations Size of specimen Encounter diffraction Many cells are transparent and colorless- staining can kill specimen

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