Enzymes Biochemistry

What You Need to Know! Enzymes work by lowering the energy of activation. The catalytic cycle of an enzyme that results in the production of a final product. The factors that influence the efficiency of enzymes.

Special Proteins: Enzyme Enzymes are proteins that speed up the rate of a chemical Rx Making/breaking covalent bonds in cells Also called a biological catalyst Suffix: -ase Enzyme Substrate(s)  product(s)

Enzymes are large 3-D proteins that have a groove where they bind the substrate(s)  active site

Enzyme Each enzyme: Has a specific 3-D structure (due to the number and order of AA) Can interact only with one type of substrate that fits in the active site: Lock and Key model

Catalytic Cycle Enzyme finds substrate Substrate binds to active site “enzyme-substrate complex”

Enzyme Rx Enzyme transforms the substrate into product “enzyme product complex” Enzyme releases product An enzyme can carry out a chemical Rx over and over again it is not used up in the Rx Substrates are used up

Activation Energy Transformation from reactants to products requires the input of energy = activation energy Enzymes can speed up a Rx because they lower the activation energy of the Rx

Enzyme Rx Rates Depend On: Substrate concentrations The more substrate, the faster the rate Until present enzymes reach capacity Enzyme concentrations The more enzymes the faster the rate Until substrate concentration becomes limiting factor pH Can slow the rate due to denaturation of enzyme

Enzyme Rx Rates Depend On: Temperature Can slow rate due to denaturation of enzyme Presence of inhibitors Can slow down or block enzymes

To be continued…

Factors that affect enzyme activity: pH Enzyme pepsin in stomach does not become active until it is in an acidic pH Temperature Each enzyme has an optimal temperature range Cofactors or coenzymes Bind to the enzyme to make it functional Ex: metals such as Zn, Fe, Co, and vitamins Inhibitors

1. Competitive Inhibitor (reversible) Mimics substrate molecule(s) (flat toothpicks) but cannot be metabolized slows down Rx rate

2. Non-competitive/allosteric inhibitors (reversible) Molecules that do not bind to active site but at the allosteric (other) site leading to conformation (change in shape) Can turn off active site

Enzymes http://www.youtube.com/watch?v=PILzvT3spCQ&feature=related

3. Non-competitive inhibitors-(irreversible) Toxins Poisons

Enzyme Regulation Chemical chaos would result if all metabolic pathways in the body work simultaneously Regulation through: Transcription/translation Active regulation of enzymes already made: Allosteric Regulation Feedback Inhibition

Active Regulation Allosteric Regulation: Feedback Inhibition: Reversible non-competitive inhibitors or activators that the body makes binds to allosteric site Feedback Inhibition: In long metaboloic pathways final products becomes allosteric inhibitors to the first enzyme