Exploring the World of Cells and Microscopy
Delve into the fascinating world of cells by discovering their sizes, from a giraffe's nerve cell to a human egg, and learn about different types of cells like cheek cells and onion cells. Explore the use of electron microscopes for detailed imaging, compare light and electron microscopes, and understand the workings of a scanning electron microscope. Discover the magnification capabilities, resolution differences, and types of radiation used in light and electron microscopes. Uncover the preparation processes and costs associated with each type of microscope.
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Presentation Transcript
How big are cells? Nerve cell from a giraffes neck - 3m Human kidney - 13cm Human egg - 100 m Sperm cell - 55 m Cilia - 10 m Red blood cell - 9 m Mitochondrion - 2 m HIV virus - 100nm Ribosome - 20nm Units for measurements Millimeters - mm Micrometers - m Nanometers nm 1mm = 1000 m 1 m = 1000nm
How big are cells? plasma membrane A p p r o x i m a t e l y 6 0 m i n d i a m e t e r Cheek cell cytoplasm nucleus
How big are cells? Onion cells A p p r o x i m a t e l y 2 0 0 m i n d i a m e t e r
To see more detail an electron microscope can be used Electron microscopes use an electron beam instead of light, which is focussed using electromagnets. The specimen has to be specially prepared and held inside a vacuum chamber from which the air has been pumped out (because electrons do not travel very far in air). The image is formed as a photograph (called an electron micrograph) or as an image on a TV screen.
Electron microscope high voltage electron gun Specimen is dead and dehydrated. Black and white image [or false colour]. Objects can be magnified up to x500000! anode condenser lens specimen objective aperture lens Intermediate lens projector lens fluorescent screen
Comparing light and electron microscope Light microscope Electron microscope Magnification x1500 X500,000 Resolution 250nm 0.25nm Type of radiation used Light Electrons Focussed by Glass lenses Electromagnets Type of material that can be viewed Living/moving/dead/abiotic Dead/abiotic Size Small and portable Large and static Preparation and cost of material Cheap and easy Difficult and expensive
Scanning Electron Microscope (SEM) Work in a similar way like Transmission Electron Microscope (TEM)but are designed to make images of the surfaces of objects.
