OCR Gateway Biology B3 Molecules of Life

Cell structure
1. The number of mitochondria in cytoplasm depends on the activity of the cell.
  1. Respiration happens in mitochondria.
  2. More mitochondria needed when cells need more energy.
2. Ribosomes are smaller than mitochondria, also in cytoplasm, site of protein synthesis.
DNA and protein synthesis
1. Nucleus contains genes.
  1. Each gene is a section of a chomosome.
    1. Made of two strands of DNA coiled to make double helix.
      1. Stands connected by cross links made by pairs of bases.
2. Four bases are A+T, C+G.
  1. They undergo complimentary base paring.
3. Proteins are formed at the ribosome.
  1. Proteins are made of long chains of amino acids.
    1. Amino acids are coded for by a sequence of three bases.
4. DNA can't leave the nucleus.
  1. A molecule of mRna takes a copy of one strand of DNA to the ribosome.
5. Many proteins are enzymes, which control activity of the cell.
Finding DNA structure.
1. Watson and Crick used data from other scientists.
  1. X-ray photographs which showed DNA had two chains.
  2. Data saying bases occur in pairs.
  3. They found the structure in 1953.
    1. Nobel Prize in 1962 - other scientists needed to check the discovery.

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