Living and growing.

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  • Living and growing.
    • Mitochondria and Ribosomes
      • Mitochondria are structures in cells where respiration happens. Ribosome's are too small to see using the light microscopes.
      • Chromosomes are made from DNA. Genes are short sections of DNA.
        • Some cell structures are too small to be seen with the light microscope. Ribosome's are like this.
        • They are found in the cytoplasm and are the site of protein synthesis. They can only be seen using an electron microscope
      • Each gene is a set of coded instructions for a different protein. Mitochondria are tiny structures found in cells, one is called a mitochondrion.
        • Respiration, the chemical reaction that releases energy from glucose, happens in mitochondria. This provides energy for life processes such as movement and growth.
        • Tissues and organs that need a lot of energy have a lot of mitochondria in their cells. For example liver cells and muscle cells need a lot of mitochondria.
    • Chromasomes and DNA.
      • The cells nucleus contains chromosomes. These are long, coiled molecules of DNA, divided up into regions called genes.
      • The information contained in genes is in the form of coded instructions called the genetic code. The genetic code controls cell activity which means that it also contains some of the characteristics of the organism.
      • DNA controls the production of different proteins. They are needed for the growth and repair of cells.
    • The structure of DNA.
      • Two scientists, James Watson and Frances Crick, worked out the structure of DNA. By using data from other scientists they were able to build a model.
        • In DNA, two strands coil together to create a double helix. There are chemical cross-links between the two strands, formed by pairs of bases.
        • Each gene in a molecule of DNA contains a different sequence of bases and codes for a particular protein. Proteins are made in the cytoplasm of the cell, not in the nucleus.
      • The data they used showed that bases occurred in pairs. Further x-ray data showed that they were two chains wound into a double helix.
        • Genes cannot leave the nucleus so a copy of the gene is needed. This copy is able to leave the nucleus and enter the cytoplasm so that the cell can make proteins.
      • Each strand of DNA is made of chemicals called bases. There are four different types of bases A,T,C and G.
    • Making proteins.
      • Protein structure is determined by the DNA base code. Proteins are made from lots of amino acids joined together.
        • Ribosome's are the site of protein synthesis. They are found in the cytoplasm but DNA is found in the nucleus.
        • The genetic code needed to make a particular protein is carried from the nucleus to the ribosome's by messenger RNA. mRNA from DNA is called transcription
      • Each amino acid is coded by three bases. The sequence of the bases determines the sequence of the amino acids in a protein molecule.
        • Proteins from mRNA is called translation.
      • DNA controls the working of the cell by controlling its production of proteins. Some of these proteins are enzymes.


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