Biology OCR AS level Cell Structure

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  • Created by: meg
  • Created on: 13-05-13 18:30
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  • Cell Structure
    • All living organisms are made of a cell or a collection of cells. Cells and their contents are usually measured in micrometres. 1 micrometre is one thousandth of a millimetre
    • Specimens to be viewed using a microscope are usually stained to make parts of them look darker or different colours
    • Plant and animal cells are eukaryotic cells, with a nucleus surrounded by an envelope. The nucleus contains the DNA, in the form of chromosomes   All cells are surrounded by a partially permeable membrane.
    • Plant and animal cells contain ribosomes for protein synthesis, endoplasmic reticulum for the storage & transport of substances made in the cell, golgi apparatus for processing & packaging proteins, lysosomes containing digestive enzymes & mitochondria to produce ATP by aerobic respiration.
    • Bacteria are prokaryotic cells, which do not have a nucleus. Their DNA is not associated with histones, and is present as a circular strand. It is attached to the plasma membrane. Prokaryotic cells lack complex membrane-bound organelles such as mitochondria. They have similar ribosomes than eukaryotic cells. They always have a cell wall but it is made of peptidoglycan not cellulose
    • Animal cells contain a pair of centrioles, which organise the the microtubules in the cell, e.g. when forming the spindle during cell division. Animal cells may also have cilia or flagella.
    • Microtubules & microfiliments form the cytoskeleton, holding the cell in shape & helping to move organelles around in the cell


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