BTEC National Applied Science Biology 2022/2023

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Cell theory Cell theory is the understanding that all living things are composed of cells and that cells are basic unit of life, all cells come from Pre existing cells 1665 Robert Hook descri... bed cells 1674-1683 Anton Van Leeuwenhoek observed first cell invented telescope 1839 Theodor Schwann developed cell theory 1860 Louis pasteur showed bacteria will only grow in sterile rich solutions in air Disproved theory of spontaneous generation of cells Eukaryotes Have DNA in nucleus membrane bond (organelles) Prokaryotes Have free DNA (not in nucleus) No organelles (only ribosomes) Light Microscope -Developed in 17th century -Magnify up to 2000x -able to magnify living specimen -focuses light to show the object -Cheaper Electron Microscope -Developed in 1930 -Magnifying 200000 -Sees substance of cells -Expensive -Shorter wave lengths -higher magnification -higher resolution TEM Transmission electron microscope 2D SEM Scanning electron microscope 3D Magnification The degree to which the size of an image is larger than the image itself Resolution It's the degree to which it's possible to distinguish two close objects together Calculating magnification Eyepiece X objective magnification = overall magnification Cell magnification from image Actual size = image size/Magnification [Show More]

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