PROTEINS:
Proteins are macromolecules that contain the elements carbon, hydrogen, oxygen and nitrogen.

Proteins are found in all living organisms and their structures making up approximately 50% or more of the cells dry weight.


ROLE OF PROTEINS:

Proteins are used in forming cell structures such as keratin found in hair.
Proteins are used to speed up reactions (catalyst) called enzymes.
Proteins aid in the transportation of other substances across the cell membrane
(active transport) as well to transport molecules such as hemoglobin which is found in blood.
Proteins are used in movement (i.e. actin and myosin fibers of muscles)
Proteins are also used as chemical messengers to produce hormones ( insulin)
Proteins are made up of amino acids (protein building blocks)

AMINO ACIDS:

Amino acids (a.a.) are the monomers (building blocks) of proteins. All amino acids have a general structure. This is the amine group attached to a carbon, then followed by a carboxyl group as well. * Note the “R” side chain. * This side chain is what gives each of the 20 amino acids their unique qualities.
*see diagram from today’s class notes*

There are 20 different amino acids (a.a.). Our human bodies only produce 12 of them on our own. However we need all 20 to function so we must obtain the other 8 a.a. by food sources. These 8 a.a. are called the essential amino acids.

HOW TO BUILD A PROTEIN:

When joining a.a. together the carboxyl group from the amino acid will react with the amine group of another a.a. This will create a condensation reaction, which results in the formation of a dipeptide. (2 a.a. bound together by a peptide bond).
*see diagram from today’s class notes*

As you continue to link together two a.a. to another one or more you will begin to form a polypeptide chain. Once this chain becomes long enough this chain will fold into a 3-D structure which will determine the function of the protein being built. * Refer to page 16 in your text for illustrations and correct naming of all 4 structure types.*

However, if one of these protein molecules is exposed to extreme temperatures, pH conditions, or harsh chemicals the protein will unfold or change its intended shape. This protein will have become denatured. A denatured protein will not function as it was intended to be and can cause side effects within an organism.


HOMEWORK:
1. What is the monomer of a protein?
2. Why are they so important to living things?
3. How are dipeptides and polypeptides similar?