How Enzymes Function 5.5-5.9

How is the net change in energy from the beginning to the end of a reaction different with an enzyme?

The net change of energy is the same with and without an enzyme.

Why is adding heat NOT an effective way to sped up reactions in a cell?

-ALL of the reactions in a cell would speed up, not just the necessary ones -A cell would die if there was too much heat because the heat would denature proteins

Coenzyme

-An organic cofactor -Most are made from vitamins or are vitamins -Ex. vitamin B6

pH levels and enzyme function

-At very low pH, extra hydrogen ions affect some of the chemical bonds that allow an enzyme to keep its structure -When the pH level is not where it should be, enzyme action may be negatively affected, and this can affect the functioning of the cell.

Feedback Inhibition

-Beneficial inhibition that is one of the most important mechanisms that regulates metabolism -If a cell is producing too much of a product, the product may inhibit one of the enzymes that allows the product to be produced -The can occur in ATP production

Names of Enzymes

-Most end in -ase -Many enzymes are named for their substrate

Cofactors

-Nonprotein helpers -Many enzymes will not function without them -May be inorganic substances (Ex. ions of zinc, iron, or copper) -Organic cofactors are called coenzymes

Irreversible Inhibition

-Occurs when an inhibitor attaches to an enzyme by covalent bonds -Often, toxins and poisons are examples

Reversible Inhibition

-Occurs when weak bonds bind an inhibitor and an enzyme -Hydrogen bonds are an example of weak bonds

How have humans used enzymes in beneficial ways?

-Pesticides such as malathion and parathion -Beneficial drugs such as penicillin, ibuprofen and aspirin reduce pain, and HIV and cancer drugs,

How have humans used enzymes in destructive ways?

-Poisons -Cyanide, nerve gasses like Sarin,

Enzyme

-Protein molecule -Speeds up reactions by lowering the energy of activation barrier -Is not changed into a different molecule as it works -Without enzymes, most metabolic reactions would not occur quickly enough to sustain life

Competitive Inhibitor

-Similar to the enzyme's normal substrate -Competes with the substrate for the active site on the enzyme -Blocks substrates from entering the active site of an enzyme to make the enzyme less productive -Can be overcome by increasing the concentration of substrate molecules

Induced Fit

-The active site of an enzyme slightly changes shape when a substrate binds to an enzyme -It does this to embrace the substrate more snuggly -May strain the bonds of the substrate or put chemical groups of the active site in the correct position to speed up the reaction.

Energy of Activation (EA)

-The amount of energy that reactants must absorb to start a chemical reaction -An energy barrier that must be overcome before a chemical reaction can occur

Active Site

-The region on an enzyme that the substrate fits into. -Usually a pocket or groove on the enzyme's surface -Fits only one kind of substrate molecule

Why does the cellular environment affect enzyme activity?

-The shape and structure of an enzyme determine its function because it is a protein -Changes in the environment affect the shape of the enzyme.

How does temperature affect an enzyme?

-The temperature that is best for the enzyme produces the highest rate of contact between reactant molecules and the active site of the enzyme. -Temperatures that are too high denature the enzyme

What are the steps of the catalytic cycle of an enzyme?

1) The enzyme has an empty active site and is available 2) The substrate binds to the enzyme with induced fit 3) The substrate is changed to the products 4) The enzyme releases the products

Inhibitor

A chemical that interferes with an enzyme's activity

Substrate

A specific reactant that an enzyme acts on

Why does an enzyme have a specific shape?

An enzyme has a unique 3D shape b/c it is a protein.

Why are many different types of enzymes needed to speed up all the reactions in a cell?

The active site of an enzyme only fits one type of substrate molecule.

What does the shape of an enzyme determine?

The shape of the enzyme determines which chemical reaction it will speed up.

How does salt concentration affect an enzyme?

Too much salt is not good for enzymes because the salt ions affect some of the chemical bonds that allow an enzyme to keep its structure

Noncompetitive Inhibitor

-Binds to the enzyme in an area other than the active site -This changes the shape of the enzyme so that the active site cannot fit the substrate