Chapter 16.6 & 16.7 Enzymes & Enzyme Actions SWBAT: Describe how enzymes function as catalysts and give their names Describe the role of an enzyme in an enzyme-catalyzed reaction

Introduction to Enzymes Biological catalyst which speed up biological reactions by lowering the activation energy required for them to take place Mostly made up of proteins Mot used up or chemically change at the end of the biological reaction What is an enzyme?

Introduction to Enzymes Can be used again and again Produced only when needed Catalyse reversible reactions E + S ES EP E + P E = enzyme S = substrate P = product How enzymes work?

Names of Enzymes Name describes the compound or reaction that is catalyzed Name is derived by replacing the end of the name with –ase Example: Oxidation Reaction = oxidase Dehydration Reaction - dehydronase

Names of Enzymes Some early known enzymes end in –in pepsin, rennin, trypsin Recently, classifying and naming enzymes based on the type of reaction is catalyzes

Classification of Enzymes Oxidoreductoases (Oxidation – Reduction) Transferases (Transfer groups of atoms) Hydrolases (Hydrolysis) Carbohydrases, Proteases, Lipases Lyases (Add/Remove atoms to/from a double bond) Isomerases (Rearrange atoms) Ligases (Combine molecules using ATP)

Enzyme Action Enzymes are globular proteins Unique 3-D shape that binds to a small group of reacting molecules called substrates

Active Site Area where the enzyme binds the substrate and catalyzes the reaction The active site of a particular enzyme fits the shape of only a few types of substrates Substrate Active Site

Enzyme-Catalysed Reactions Anabolic reactions Synthesis is simpler substances into complex substances Amino Acids  Polypeptides  Proteins Catabolic reactions Breakdown of complex substance into more simple substances Hydrogen peroxide  Oxygen + Water 2 H2O2  O2 + 2 H2O

Characteristics of Enzymes Speed up chemical reactions Small amount needed to catalyse a reaction because enzymes can be used again and again The shapes of the active sites make enzymes highly specific, meaning they can only interact with 1 type of substrate to form an enzyme-substrate complex

“Lock and Key” Hypothesis The active site of an enzyme molecule = lock; substrate molecule that the enzyme acts on = key When the enzyme and substrate molecules are bound together, they form an enzyme-substrate complex

“Lock and Key” Hypothesis (cont.) Substrate molecule is subsequently converted into products Product molecules leave the active site Enzyme molecule is free to bind with more substrate molecules

“Induced Fit” Model Enzyme molecule can undergo adjustments at its active site Binds more tightly with substrate molecule Facilitates binding at active site and speeds up rate of chemical reaction

Chapter 16.8 Factors Affecting Enzyme Activity SWBAT: Describe the effect of temperature, pH, concentration of substrate and inhibitors on enzyme activity

Factors Which Affect Enzyme Activity Temperature pH Concentrations of substrates in enzymatic reactions

Temperature Optimum temperature (37°C) – the temperature at which an enzyme is most active (can catalyze the most number of reactions per second) Rise in temperature (until optimum)  Increase in enzyme activity Kinetic energy of particles increases Increases chance of substrate molecules fitting into the active sites of enzyme molecules More rapid formation of enzyme-substrate complexes Increase in formation of products

Temperature (cont.) When temperature exceeds optimum temperature of enzyme activity, it starts to fall rapidly H-H bonds in enzymes break, leading to the denaturation of enzymes Unique 3-D structure lost Denaturation is irreversible

pH Optimum pH (~7.4) = maximum activity Most enzymes lose their abilities to catalyse reactions at pH 3 and pH 11 Extreme changes in pH of a solution will denature the enzyme, just like temperature

pH (cont.) Slight changes in pH is enough to change the electrostatic charges of the active site of enzyme and substrate Electrostatic repulsion occurs Inhibits the formation of enzyme-substrate complex

Substrate & Enzyme Concentrations Substrate concentration increases  rate of reaction increases Saturation of enzyme molecules (all being made use of in reaction) Reaction cannot take place Increase in enzyme concentration will increase the rate of reaction again

Animation Animation comparing Link to animation Enzymes Substrates Inhibitors Temperature pH Link to animation

Enzyme Inhibitor

Competitive Inhibition

Non-Competitive Inhibition