how did the electron microscope contribute to our knowledge of cells?
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It's because of its better resolution NOT magnification. Magnification is just the number of times the image is larger than the object.\n The Resolution however can be defined as the ability to distinguish between two seperate points.If two seperate points cannot be resolved , they will be seen as 1 point. Excited elecrons behave like electromagnetic waves and have a much shorter wavelength than the shortest wavelength of visible light.. therefore have a higher resolution , as a result the nuclear envelope , nuclear pore, the double membrane of mitochondria ..etc can be seen with the electron microscope even with the same magnification of the light microscope...
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yes its it called the scannig electron microscope I believe
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Cell theory history\nIn 1838, the botanist Matthias Jakob Schleiden and Theodor Schwann, a physiologist discovered that both plant and animal cells had nuclei. From this realization, they surmised that all living things were composed of cells. In 1839, Schwann published 'Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals', which contained the first statement of the cell theory.\n\nSchwann and Schleiden's statement of the cell theory was:\n\nCells are the unit of structure, physiology, and organization in living things. \nCells are both a distinct entity and a building block in the construction of organisms. \nCells form by spontaneous generation.
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Gap junctions are specialized areas of the cell membranes that connects neighboring cells.
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All the answers are here --> http://en.wikipedia.org/wiki/Cell_%28biology%29\n(and in your book)
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Mitochondria are cell organelles in the protoplasm, responsible for providing the cell with energy. Due to its function, a mitochondrion is called the 'powerhouse of the cell'.
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i did this, i used a ball of styrofome( er however you spell that) for the whole cell, and a smaller ball for the nucleus. then i just found a buncha little things for everything else. i used toothpicks with little tags on the end to label the parts
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http://sun.menloschool.org/~cweaver/cells/
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it was leeuwenhoek.e also observed blood cells,sperm cells etc.That is why he is called the father of microscopy.
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atom, molecule, cell, tissue, organ, organ system, and organism\n\nThe rest is a grand surprise that only the elite few can figure out.\n\nDon't hurt yourself with the pages of your Bio book.
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I didn't know the answer to this one myself, so I looked it up, wow, I can't write it all down here sorry.  But here are some sights I was able to pull up, hopefully you can find the info you would like here.  :)  Basically from what I have gathered though, they are broken down into four groups, compound, dissection, scanning electron, and transmission electron.  The last source I listed, has a guide to help you pick the right microscope for you if you are looking to buy one.  I'm not sure if any of this will help, but I hope it will.
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electron microscope\nn.\nAny of a class of microscopes that use electrons rather than visible light to produce magnified images, especially of objects having dimensions smaller than the wavelengths of visible light, with linear magnification approaching or exceeding a million (10 to th power 6).\n\nA device that uses electrons instead of light to form images of very small objects, such as individual parts of small living things. \n\na microscope that is similar in purpose to a light microscope but achieves much greater resolving power by using a parallel beam of electrons to illuminate the object instead of a beam of light\n\nThe electron microscope is a microscope that can magnify very small details with high resolving power due to the use of electrons as the source of illumination, magnifying at levels up to 2,000,000 times. \n\nHistory \nThe first electron microscope was built by the German physicist Ernst Ruska. He knew that electrons possess a wave aspect, so he believed he could treat them in a fashion similar to light waves. Ruska was also aware that magnetic fields could manipulate electrons, possibly focusing them as optical lenses do to light. After confirming these principles through research, he set out to design an electron microscope. Ruska had deduced that an electron microscope would be much more powerful than an ordinary optical microscope, because he knew that magnification increased with shorter wavelengths. Since electron waves were shorter than ordinary light waves, it followed that they would allow for greater magnification. In 1933 Ruska and a collaborator, German physicist Max Knoll, under whom he obtained his doctorate, built the first crude electron microscope. Despite the fact that it was primitive and not fit for practical use, the instrument was still capable of magnifying objects 400 times. Ruska was later awarded the Nobel Prize in 1986 for its invention. \n\nThe first practical electron microscope was built by Eli Franklin Burton and students, Cecil Hall, James Hillier and Albert Prebus, at the University of Toronto, Canada in 1938. \n\nAlthough modern electron microscopes can magnify an object 2 million times, they are still based upon Ruska's prototype and his correlation between wavelength and magnification. The electron microscope is an integral part of many laboratories. Researchers use it to examine biological materials (such as microorganisms and cells), a variety of large molecules, medical biopsy samples, metals and crystalline structures, and the characteristics of various surfaces. \n\nTypes \nElectron beam micmroscopes \nTransmission Electron Microscope (TEM) \nThe Transmission Electron Microscope (TEM) involves a high voltage electron beam emitted by a cathode and formed by magnetic lenses. The electron beam that has been partially transmitted through the very thin (and so semitransparent for electrons) specimen carries information about the inner structure of the specimen. The spatial variation in this information (the "image") is then magnified by a series of magnetic lenses until it is recorded by hitting a fluorescent screen, photographic plate, or light sensitive sensor such as a CCD (charge-coupled device) camera. The image detected by the CCD may be displayed in real time on a monitor or computer. \n\nResolution of the high-resolution TEM (HRTEM) is limited by spherical and chromatic aberration, but a new generation of aberration correctors has been able to overcome spherical aberration. Software correction of spherical aberration has allowed the production of images with sufficient resolution to show carbon atoms in diamond separated by only 0.89 ångström (89 picometers) and atoms in silicon at 0.78 ångström (78 picometers) at magnifications of 50 million times. The ability to determine the positions of atoms within materials has made the HRTEM an indispensable tool for nano-technologies research and development in many fields, including heterogeneous catal
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I think the other answerers have a few misconceptions.\n\nThe problem with your question is the use of the word "seen."\nSo I will answer your question in two parts.\n\n1) The best visible wavelength (optical) microscopes cannot see atoms. The best they can probably do, is see some of the fine detail of biological cells, nothing more.\n\n2) Using the term loosely, electron microscopes or atomic force microscopes can "see" atoms, and even electron clouds, but one should not take the word "see" too literally.\n\nAn atomic force microscope works by moving a very fine tip  over a sample. Without going into the specifics of it, a computer can build up a model of the shape and dimensions of atoms in the sample by measuring the forces that the atoms exert on the tip.\n\nSo I will state the answer to your question as this:\n\nWe CAN OBSERVE computer images of atoms; by this i mean that we can view computer images of atoms - but these are more like graphs of interatomic forces than actually viewing atoms.\nThe highest precision that can currently be achieved is viewing the electron clouds of various atoms. We cannot directly observe anything smaller than this.\n\nSo, you might ask, how do we know about the existence of particles like electrons, protons, neutrons, or even quarks?\nWell, that's because their existences can be inferred from various experiments.\n\nE.G. Rutherford's Alpha Scattering experiment showed that atoms consist of mostly empty space (in support of our massive nucleus and electron clouds model)\n\nAnd particle physicists can use devices a bit like cloud chambers to "observe" fundamental particles like quarks by accelerating e.g. protons high speeds and then making them crash into each other. This liberates particles smaller than protons, giving evidence for the existence of quarks.\n\nHowever, these particles are "observed" by the effect that they have on the surrounding medium, not by direct observation.\n\n\nSo to sum up, the atomic force microscope is the best microscope for "viewing" atoms, but don't take this literally. It's resolution allows us to examine the electron clouds of individual atoms.\n\n\nAlso note that "Electron clouds" is also not to be taken too literally, as anyone who knows anything about quantum mechanics will tell you.
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Organelles don't have much of an effect on cell function--mostly it's its shape. More active cells are smaller than less active cells so information can quickly pass through the cytoplasm and into the nucleus. This explains why muscle cells are long, small and slender, and fat cells are large and bulky. \n\nThe membrane of smaller cells has many exterior folds to increase its surface area and ablitily to collect nutrients necessary for cell function.
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Try this , it really helped me in my first few lectures in cell bio , such as DNA and RNA . Loads of animations and stuff ! \n\nhttp://www.johnkyrk.com/DNAtranscription.html
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1839: Theodor Schwann and Matthias Jakob Schleiden elucidate the principle that plants and animals are made of cells, concluding that cells are a common unit of structure and development, and thus founding the cell theory.
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cells dont have cells but they they have organelles which are sort of like cells, which includes mitochondria, ribosomes, golgi apparatus, etc. that have various functions such as converting sugar to energy, synthesizing proteins, etc. they're sort of like minature organs if the cell was your body (hence the name organelles