What are Enzymes? Catalysts change the rate of the reaction without being altered themselves. Enzymes are biological catalysts. Enzymes are (mostly) proteins, whose three dimensional shape allows for their ability to react specifically.

How Do Reactions Occur? Spontaneous reactions may occur very slowly. All reactions require free energy of activation (EA) Uphill portion represents the EA required to start the reaction. Downhill portion represents the loss of free energy by the molecules in the reaction. DG is the difference in free energy of products and reactants.

Is this reaction exergonic or endergonic?

Allosteric inhibition

Allosteric Regulation Regulatory molecules that bind to the enzyme’s allosteric site changing the shape of the enzyme. Allosterically regulated enzymes have a quaternary protein structure. Each subunit of the enzyme has an active site and an allosteric site. Allosteric activators stabilizes the active site Allosteric inhibitors deactivates the active site.

Competitive inhibition

Noncompetitive inhibition

Enzyme Activity Temperature pH Enzyme Concentration Substrate Concentration

                                    

Cofactors Non-protein molecules that help enzymes function. Bind to active site to enhance enzymatic reactions. Cofactors may be inorganic metals such as zinc, iron, or copper. Coenzymes are organic cofactors (e.g. vitamins)