Enzymes They’re terrific, they’re specific, without them life would be horrific! Shape, Function, Action!

Enzymes Special proteins Control the rate of chemical reactions that are needed for metabolism and homeostasis Also called catalysts Not used up or changed at all during the chemical reaction – only affect the rate of the reaction

Enzyme names Almost all enzymes end in the letters –ase Named after their substrate: the substance that they act upon Example: the enzyme that works on lipids is called lipase Now you try: 1) Maltose: _________________ 2) Sucrose: _________________ 3) Lactose: _________________ 4) Proteins: _________________

Enzyme Characteristics Often large and complex proteins Some contain a non-protein component called a co-enzyme Some enzymes need their co-enzymes and will not function without them Vitamins are often co-enzymes

Enzyme Shape Made of polypeptide chains that are folded in a specific way The folds form pockets on the surface of the enzyme These three-dimensional pockets fit the substrate exactly The spot where the enzyme and substrate come together is called the active site When they are bonded together, they are called an enzyme-substrate complex

                                                                                                           The image shows a substrate based inhibitor in the GT region (blue) of the PBP2 enzyme that blocks bacterial cell wall synthesis. The GT region of the PBP2 enzyme is responsible for creating a sugar chain from the individual lipid II molecules. Illustration: Courtesy of Natalie Strynadka

Lock and Key Model The enzyme’s active site has a unique 3-D shape The enzyme and substrate form a complex when they bond together The substrate fits the active site like a key fits a lock In many cases a substrate will be broken into two products by an enzyme

Water is added to split this sugar. What is this process called? What is another word for catalyst? What do you notice about the end products?

Factors Influencing Enzyme Action Temperature Enzyme / Substrate concentrations pH

Temperature on Enzyme Action Affects the rate of the reaction Up to a point, as temperature increases so does the rate of the reaction Optimum temperature: the temperature at which the enzyme works best Above this temperature, enzyme function decreases Denaturation: when the 3-D shape of the enzyme is warped at the active site It basically melts It no longer fits the substrate (so the reaction won’t occur)

Temperature on Enzyme Action In humans, normal body temperature is: 37 degrees Celsius So, the optimum temperature for most human enzymes is: 37 degrees Celsius Denaturation begins at 40 degrees

Enzyme / Substrate Concentrations High enzymes with low substrate = slow rate of reaction If the concentration of substrate increases, the rate of reaction increases When everyone is in the game, the rate levels off

pH pH scale measures H+ ion concentration Goes from 0 – 14 Below 7: Acidic Above 7: Basic 7 is Neutral Optimum pH: the level at which an enzyme works best at

pH Blood is neutral (pH of 7), so most enzymes in the blood work best at a pH of 7 The stomach is very acidic. Pepsin (a digestive stomach enzyme) works best at a pH of 2 The small intestine is basic. Trypsin (an enzyme in the small intestine) works best at a pH of 8.