C. Phospholipids: form the cell membrane for ALL cells, water cannot pass through the membrane but can pass through channels in the cell.

     III.  Proteins: building blocks of life. Long chains of Amino Acids. There are 20 different amino acids in organisms.  All living things are made of the same amino acids, just in different order.
         A. 4 levels of Protein structure:
             1. Chain of Amino Acids-Primary structure (1^0) long chains  of amino acids are non-functional.
             2. Hydrogen Bonding will now cause the chain to begin to "fold up" on itself - 1 and or 2 distinct structural configurations occur:
                 a. Alpha Helix ex: hair                       b. Beta Sheet ex: silk
                                                   

        

Some proteins function at this level- All are structural proteins. Secondary Structure (2^0)

                  3. Interactions between R-groups form the Tertiary Structure (3^0) Globular  This shape determines the function of the protein, change it and the function changes.Most proteins function at this level. Some proteins are multi-globular. - 2 or more polypeptides.