1 Enzymes

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3 What Are Enzymes? Most enzymes are proteins Act as catalyst to accelerate a reaction Not permanently changed in the process

4 Enzymes Are specific for what they will catalyze Are reusable End in – ase - Sucrase (helps to break apart sucrose) -Lactase (helps to break apart lactose) -Maltase (helps to break apart maltose) -Lipase (helps to break apart lipids) - Protease (helps to break apart proteins)

5 How do enzymes Work? Enzymes can work by weakening bonds which lowers activation energy

Enzymes Lower a Reaction’s Activation Energy Activation Energy = energy needed to start a chemical reaction

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

Vocabulary: Reactant: The chemical going into a chemical reaction. Product: The chemical coming out of a chemical reaction.

9 Enzyme-Substrate Complex The substance (reactant) an enzyme acts on is the substrate Enzyme Substrate Joins

10 Active Site An Active site of an enzyme molecule is where the substrate binds. Enzyme Substrate Active Site

11 Two ways in which Enzyme and substrates bind 1. Lock and key model 2. Induced fit model

12 Lock and Key Model + + E + S ES complex E+ P S P P S E = Enzyme S = Substrate P= product Active site

Lock & Key Model One enzyme for every substrate unique fit Substrate Enzyme

The enzyme fits over the substrate perfectly – like a key fits a lock. It holds the starch molecule in place as a water molecule breaks the bond between two glucose particles Starch molecule Amylase enzyme

This continues until the molecule has been broken down completely

16 Induced Fit A change in the shape of an enzyme ’ s active site Induced or altered by the substrate

17 Enzyme Action: Induced Fit Model Enzyme structure flexible, not rigid Enzyme and active site adjust shape to bind substrate

18 Enzyme Action: Induced Fit Model E + S ES complex E + P S P P SS

19 Factors Affecting Enzyme Activity Temperature pH Cofactors & Coenzymes Inhibitors

20 Temperature & pH High temperatures are the most dangerous reactions & denature enzymes (Most like normal body temperatures) Lower than optimal temperatures just decrease the rate of reactions Most enzymes like near neutral pH (6 to 8) Denatured (unfolded) by ionic salts and metal ions

21 Factors Affecting Enzyme Action Optimum temperature Reaction Rate Low High Temperature

22 Factors Affecting Enzyme Action Reaction Rate Optimum pH pH

23 Cofactors and Coenzymes Inorganic substances (zinc, iron) and vitamins (respectively) are sometimes need for proper enzymatic activity. Example: Iron must be present in the protein structure of hemoglobin in order for it to pick up oxygen.

24 Factors Affecting Enzyme Action Maximum activity Reaction Rate substrate concentration

25 Enzyme Inhibition Inhibitors Cause a loss of catalytic activity Change the protein structure of an enzyme May be competitive or noncompetitive Poisons and drugs are examples of enzyme inhibitors.

26 Competitive Inhibition A competitive inhibitor Has a structure similar to substrate Occupies active site Competes with substrate for active site Has effect reversed by increasing substrate concentration

27 Noncompetitive Inhibition Does not have a structure like substrate Binds to the enzyme but not active site Changes the shape of enzyme and active site Substrate cannot fit altered active site No reaction occurs Effect is not reversed by adding substrate