23.2

By Abbie
 * 23.2. Amino Acids and Proteins**

__Amino Acids - The Basics__ __The Structure of Amino Acids__ There are 20 amino acids that all have the same basic structure.
 * Amino Acids are the basic building blocks of proteins.
 * By definition, Amino Acids are organic molecules that contain two functional groups: A basic NH2 amino group and an acidic (-COOH) carboxylic acid group.



__Amino Acid Reactions__ Amino Acids react with each other. Basic Amino Group (of one amino acid) + Acidic Carboxylic Acid Group (of another amino acid) > peptides + water __peptide bond__ - a bond formed as a result of the amino acid reaction __dipeptide__ - the product of the reaction because it is made up of two amino acid units. __polypeptides__ - longer chains __proteins__ - chains of 50 or more amino acids. __proteases__ - enzymes that break peptide bonds.


 * Amino Acids are extremely important to a protein chain because the difference of only one can cause a big change in a protein's activity in a cell.
 * Amino acid side chains also determine the shape and the structure of proteins.
 * A __primary structure__ is the sequence of the amino acids in a polypeptide chain or protein.
 * A __seconday structure__ describes how the chain is coiled or arranged.
 * __Tertiary structures__ are the three-dimensional shapes of protein.
 * __Quaternary structures__ are the four different polypeptides of hemoglobin.