Function: build structural materials and carry out cell metabolism.

    Act as hormones, enzymes or carrying molecules.

    Help transport substances into/out of a cell.

    Help fight disease.

    Make up keratin (nails), collagen (connective tissue) and muscle.


    made out of C, H, O and N (sometimes S)


Proteins are long polymers of monomers called amino acids.

    proteins are sometimes called polypeptides.


Amino acids: 

    defined as the building blocks of proteins.

    joined together by a covalent bond called a peptide bond.

    there are 20 different amino acids make up all of the proteins.

    13 of the amino acids are essential.


Structure of an amino acid: 



1. amine group (-NH2)

2. carboxyl group (-COOH)

3. R-group (differs for the 20 different           amino acids)



R-groups can be acidic or basic, polar or nonpolar.  Some contain carbon rings.


Proteins have four levels of organization:



1.  the sequence of amino acids.

2.  amino acids within a chain can be twisted or folded.

3.  the chain itself can be folded resulting in a 3-dimensional shape.

4.  specific folded protein chains (shapes) fit together like puzzle pieces.


Proteins can be denatured (they lose their 3-D shape) by high heat or strong acids and bases.


Chemical Reactions

A chemical reaction is a process that changes one set of chemicals (the reactants) into another set of chemicals (the products.)

    Whenever chemical bonds are broken, energy is released. Sometimes occurs spontaneously and other times needs a boost of energy.

    Whenever new chemical bonds are made, energy is absorbed and stored. Usually requires a boost from a source of energy.

    The activation energy (Ea) is the energy need to get a reaction started.




Enzymes: are a special type of protein that acts as a biological catalyst.


Catalysts speed up a chemical reaction by lowering the Ea but is not affected itself




Enzymes also provide a site where reactants can be brought together to react.


Substrate: the reactants of enzyme-catalyzed reactions.


Active site: an area of the enzyme that fits like a lock and key with the substrate (very specific). The active site and the substrate have complementary shapes.




Draw a picture:

Label enzyme, substrate, active site, enzyme-substrate complex and products.