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Proteins are one of the four macromolecules that compose living organisms. They play many roles in living systems- whether you are a one-celled bacterium or an extremely complex multicellular organism- like us! Proteins are components of muscles and bones, they serve as enzymes which digest food and run metabolic pathways, they play a major role as antibodies which recognize foreign invaders in the body, and they serve as messengers and carriers in the body. Below I've listed some specific proteins and their functions. As you can see, we rely heavily on our proteins.

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Examples of Important Proteins:
1. Isomerase- a protein which is an enzyme which converts a molecule to one of its isomer forms (remember, glucose, fructose, and galactose are isomers- they have the same chemical formula but different structures- isomerases can convert simple sugars to glucose!)
2. Insulin- a 51 amino acid long polypeptide chain that helps regulate the blood sugar level by "encouraging" the liver to convert excess glucose into glycogen to be stored
3. Antibody- a protein that recognizes a specific foreign invader, such as a bacterium or virus, and marks this invader for destruction by the immune system

The Basics of Proteins

1. The monomers of proteins are amino acids. The polymer, if it is a single chain of amino acids, is a polypeptide chain. If the polypiptide chain goes through the quarternary structure formation (see below) it will consist of several polypeptide chains that bond to one another- the typical form of proteins.

aminoacidstructure.jpg

2. Amino acids are hooked together through dehydration synthesis. This means an -OH group is removed from the carboxyl group and a -H is removed from the amino group. The -OH in conjunction with the -H form a water molecule (H2O).
dipeptide_ex.gif



3. In order to function, a protein must fold. The R groups of amino acids control how the protein will fold. R groups will either be polar or nonpolar, meaning they will be hydrophobic or hydrophilic.
aminoacids.gif

4. The function of a protein is completely determined by how the protein folds. A protein must fold correctly in order to do its job. There are four levels to protein folding.
protein_structure.jpg
Above image credited to: http://schoolworkhelper.net/2010/11/protein-structures-primary-secondary-tertiary-quaternary/


Protein Folding: http://intro.bio.umb.edu/111-112/111F98Lect/folding.html



Amino Acids: [[http://matcmadison.edu/biotech/resources/proteins/labManual/images/amino_000.gif ]]