Cells and cell processes

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  • Created by: Nadia
  • Created on: 05-01-13 18:11
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  • cells and cell processes
    • was first suggested by german scientists Schwann and Schleiden but has been developed  since
    • microbes include bacteria, viruses, fungi and unicellular algae
      • bacterial/ yeast cells differ in various ways from typical animal/plant cells
        • bacteria reproduce asexually by splitting in two
          • bacteria may have been the earliest forms of life
        • yeast reproduces asexually by budding
      • viruses have simple structures and can only reproduce inside host cell
    • animal +plant cells share certain features- nucleus, cytoplas, cell membrane  but plants have cell wall, vacuole + chloroplasts
    • chemical reactions in cells are controlled by enzymes (biological catalysts)
      • shape of an enzyme allows it to join with its substrate
      • each enzyme has optimum pH and temp.
        • boiling denatures most enzymes by changing their molecular shape
      • biological washing powders contain digestive enzymes to help break down stains+allows lower washing temps.
    • proteins are made up of a chain of amino acid molecules, folded to form a specific shape
    • DNA is made of 2 long chains of alternating sugar/ phosphate molecules connected by bases.
      • structure twisted into double helix
      • there are 4 bases (A,C,G,T) the order of the bases controls the order of amino acids together to form proteins
    • cell division by mitosis enables organism to grow, replace, repair cells
      • in mitosis, the num. of chromosomes remains constant + daughter cells are genetically identical to mother cell
    • cell division by meiosis forms gametes
      • the number of chromosomes is halved, daughter cells not identical
      • mitosis produces 2 daughter cells + meiosis produces 4 cells
        • cell division by mitosis enables organism to grow, replace, repair cells
          • in mitosis, the num. of chromosomes remains constant + daughter cells are genetically identical to mother cell
    • plants+ animals have different patterns of growth
      • animals grow to a certain size, plants grow their whole life
      • plants have a spreading, branched form +animals have compact form
    • mature tissues have lost the ability to differentiate into different forms
      • certain cells are still capable e.g. bone marrow
      • human stem cells can replace damaged tissue+be basis of treatments
        • human stem cells can be obtained from embryos/ umbilical cord
        • plants have stem cells in their shoot/ root tips

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