Transcript cells
Microscopy Maurice Wetherall University Senior College Microscopy “This material has been developed as a part of the Australian School Innovation in Science, Technology and Mathematics Project funded by the Australian Government Department of Education, Science and Training as a part of the Boosting Innovation in Science, Technology and Mathematics Teaching (BISTMT) Programme.” Microscopes • Our knowledge and understanding of the structure of cells has only been possible as a result of the use of microscopes. • Light microscopes were first used in the 16th century. • The electron microscope was developed in the 1930’s. Anton Van Leeuwenhoek’s Simple Microscope - 1670 An English Tripod Microscope from around 1680 A 19th Century Microscope A Current Compound (Light) Microscope Image From Light Microscope: Onion Root Cells X1000 Compound Light Microscope • Light from a light source is directed through the specimen. • A combination of lenses is used to increase the resolving power of the human eye up to 500 times. • Resolving power (or resolution) refers to the ability to distinguish fine detail. Compound Light Microscope • The magnifying power is calculated by multiplying the individual powers of the eyepiece (ocular) and objective lenses. • e.g. 10x eye-piece, 40x objective = 400x • Field diameter is the actual distance across the field of view. • As magnifying power increases the field diameter decreases proportionally. Compound Light Microscope • The amount of light passing through the specimen can be adjusted using the iris diaphragm. This changes the contrast. • The condenser lens is used to concentrate light on the specimen. Amoeba X1000 • The following is a short movie of a living amoeba magnified 1000X through a compound light microscope • An amoeba is a microscopic unicellular animal that lives in water • Note the cytoplasmic movement, and also the way the whole cell moves. Amoeba X1000 Phase Contrast Microscope • This is a special type of light microscope, which provides greater contrast. • Structures, which could not usually be seen without staining, show up. • Staining cells kills the cells. • Phase contrast microscopes can be used to observe living cells. • e.g. movement of chromosomes during mitosis can be viewed. Transmission Electron Microscope (TEM) • In an electron microscope, beams of electrons are focussed using magnetic lenses. • The resolving power produced is up to 500,000 times greater than the human eye. • Because a vacuum is needed, tissue has to be specially prepared, and so living cells cannot be examined. Transmission Electron Microscope (TEM) Mitochondria • The following slide shows mitochondria viewed through a transmission EM • The internal structures of the mitochondria are visible. They are not visible through Light Microscopes. Rough Endoplasmic Reticulum • The following slide shows a section of rough endoplasmic reticulum. • These flattened membranes are involved in synthesis and transport of proteins in cells. • The small, dark dots are ribosomes. Smooth Endoplasmic Reticulum Electron Micrograph of Golgi Body Scanning Electron Microscope • An electron beam scans the surface of the specimen, • Electrons are reflected off, and collected by a special electron detector. • This provides an image, which appears on a computer screen and gives an impression of the outer shape of the specimen. Scanning Electron Microscope at Adelaide Microscopy • The following slide shows Year 11 students using one of the scanning EMs at Adelaide Microscopy. Human Hair in a Scanning Electron Microscope • The following specimens show human hair, the first one is hair in good condition and is from a person using shampoo and conditioner that are free of Sodium Laurel Sulfate and Propylene Glycol • The second is of poor quality hair from a person using shampoo and conditioner containing Sodium Laurel Sulfate and Propylene Glycol The End