Enzymes

What Are Enzymes? Most enzymes are proteins Act as catalysts to accelerate a reaction Not permanently changed in the process Can be reused

Enzymes Are specific for what they will catalyze Are reusable End in –ase -Sucrase -Lactase -Maltase

How do enzymes work? Enzymes work by weakening bonds of the reactant, which lowers activation energy (energy needed to start the reaction)

Enzymes Without Enzyme With Enzyme Free Energy Progress of the reaction Reactants Products Free energy of activation

Substrates The substance (reactant) an enzyme acts on is the substrate Joins Substrate

Active Site A restricted region of an enzyme molecule which binds to the substrate. Active Site Enzyme Enzyme + Substrate = ENZYME-SUBSTRATE COMPLEX Substrate

How does a substrate fit with its enzyme? TWO MODELS: 1.) Lock-and-Key Model 2.) Induced Fit Model

Lock-and-Key Active Sites are SPECIFIC and COMPLEMENTARY for their substrates. This is like a LOCK & KEY Idea of “1 substrate for 1 enzyme”

Induced Fit A change in the shape of an enzyme’s active site Induced by the substrate Idea that 1 enzyme can have more than 1 substrate. Is still specific for its substrates, but may be more than 1

Induced Fit A change in the configuration (shape) of an enzyme’s active site Induced by the substrate. Enzyme Active Site substrate induced fit

What Affects Enzyme Activity? Three factors: 1. Environmental Conditions 2. Cofactors and Coenzymes 3. Enzyme Inhibitors

Environmental Conditions 1. Extreme temperatures are the most dangerous - High fevers 2. pH (most like 6 - 8 pH near neutral) 3. Ionic concentration (salt ions) ALL OF THESE FACTORS DISRUPT THE SHAPE OF THE ENZYME, SO IT WILL UNFOLD (DENATURE)

Cofactors and Coenzymes 1. Metal ions (zinc, iron) = Cofactors (nonorganic) 2. Vitamins (biotin, B12) = Coenzymes (organic) Sometimes need for proper enzymatic activity…help to further speed up the reaction Example: Iron (Cofactor) must be present in the structure of hemoglobin in order for it to pick up oxygen.

Enzyme Inhibitors: 1st Type 1. Competitive inhibitors: chemicals that resemble an enzyme’s normal substrate and compete with it for the active site. Enzyme Substrate Competitive inhibitor

Enzyme Inhibitors: 2nd Type 2. Noncompetitive inhibitors: Inhibitors that do not enter the active site, but bind to another part of the enzyme causing the enzyme to change its shape, which in turn alters the active site. Enzyme Noncompetitive Inhibitor Substrate active site altered

POINTS TO REMEMBER Most are PROTEINS Act as CATALYSTS  ACTIVATION ENERGY SPEED  Reactions Provide an ACTIVE SITE to bind to its substrate and form an enzyme-substrate complex Are SPECIFIC for its substrate(s) Are REUSABLE (after converting a reactant to product, can do this multiple times!)