5.   What is the relationship between the water-soluble vitamins and enzyme
      function? Find out which vitamins are related to which enzymes and which
      disease or deficiency state results when that vitamin is missing. You can
      research this problem in the library. Ask a physician or pharmacist for
      advice.
    Enzymes are proteins. The word protein is from the Greek protos, meaning ‘‘first,” or
                       ‘‘of prime importance.” This very important group of biochemical molecules are
                       indeed, of prime importance. They are found in every living cell and they are
                       extremely diverse in form and function. No other biochemical substance serves so
                       many different functions as proteins. Proteins also provide the primary structural
                       component of the cell and also direct the synthesis of cellular materials. Proteins are
                        for transporting materials in the body, including oxygen, ions, lipids, and
                       other substances to the cells where they are needed for metabolism.
                       All proteins share common features. They are very large molecules with molar
                       masses ranging from 5,000 to several million daltons.  Such molecules are often called
                       macromolecules.  In addition to containing carbon, oxygen, and hydrogen, all proteins
                       contain nitrogen and some contain sulfur. When proteins are consumed as nutrients,
                       it is necessary to remove the nitrogen and excrete it. Some animals excrete nitrogen
                       as ammonia, but ammonia is toxic to humans and nitrogen is excreted as the
                       compound called urea. The most important feature of proteins is that they are all
                       polymers of smaller units called amino acids.

                      Amino acids are compounds containing
                      both an amino group and a carboxylic acid
                      group. All amino acids found in proteins
                      have these two groups on the same carbon
                      atom.
                      Of 150 known amino acids, only about 20             
                      commonly occur in human protein. Eight
                      of these common amino acids cannot be
                      synthesized by the body and must be
                      included in the diet. These are called
                      essential amino acids. All of these amino acids have the basic structure as shown,
                      and differ only in the group attached to the carbon atom bearing the amino and
                      carboxylic acid groups. Natural amino acids have the L-configuration. Three typical
                      amino acids are:

                            
 
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