Slide 1 / 64 Slide 2 / 64 Biology Enzymes 2015-08-28 www.njctl.org Slide 3 / 64 Vocabulary Click on each word below to go to the definition. activation energy enzyme active site feedback inhibition allosteric regulation induced fit catalyst noncompetitive inhibitor coenzyme optimal pH cofactor optimal temperature competitive inhibitor substrate
Slide 4 / 64 Enzymes Unit Topics Click on the topic to go to that section · Enzymes, Catalytic Cycle · Temperature, pH, Inhibition · Allosteric Regulation, Feedback Inhibition Slide 5 / 64 Enzymes, Catalytic Cycle Return to Table of Contents Slide 6 / 64 Catalysts A catalyst is a substance which speeds up chemical reactions without being changed by the reaction. When a catalyst is present, less energy is needed to start a chemical reaction. When a catalyst is present, the speed of a chemical reaction is faster. The catalyst remains unchanged at the end of the reaction.
Slide 7 / 64 Enzymes Enzymes are catalysts in biological systems. In early cells, enzymes were made of ____________. In modern cells, enzymes are a type of ___________. Slide 8 / 64 Common Enzymes Lactase is an enzyme that helps us to digest dairy products. People with lactose intolerance have trouble digesting dairy because they lack this enzyme, but they are able to take a lactaid pill that contains the enzyme lactase. Slide 9 / 64 Common Enzymes Amylase is an enzyme found in human saliva. It begins the chemical process of digestion. Typically, you can identify an enzyme by its -ase ending.
Slide 10 / 64 Enzyme Substrate Complex Enzymes help chemical reactions occur by providing a space called an active site for the substrates (reactants), to bind. substrate Active site Substrate Products leaving Enzyme/substrate Enzyme/products entering active site of complex complex active site of enzyme enzyme Click here to see a video on Enzymes Slide 11 / 64 Induced Fit Just as a key can only open a specific lock, each enzyme has its own unique shape, so each enzyme is specific to certain substrates. As the substrates enter the active site, the enzyme's shape changes just a little in order to create a better fit, called an induced fit. Slide 12 / 64 Catalytic Cycle of an Enzyme An enzyme is capable of being used again and again to allow more of the same reactions to occur.
Slide 13 / 64 1 Which of the following acts as a catalyst in the body? A Carbohydrates B Nucleic Acids C Lipids D Enzymes E Water Slide 14 / 64 Another name for protein reactants is _____. 2 A products B substrates C active sites D enzymes Slide 15 / 64 3 Enzymes bind only to certain substrates. True False
Slide 16 / 64 4 An enzyme can only be used for one reaction and then it will not work again. True False Slide 17 / 64 Activation Energy Enzymes work by decreasing the minimum amount of energy required for reaction. This is called the activation energy, E a . Just as a ball cannot get over a hill if it does not roll up the hill with enough energy, a reaction cannot occur unless the molecules possess sufficient energy to get over the activation energy barrier. Slide 18 / 64 Potential Energy Diagrams This activation energy is usually needed to break bonds in the substrate. final energy initial energy
Slide 19 / 64 Catalysts Enzymes increase the rate of a reaction by decreasing the activation energy of the reaction. This graph shows the decomposition of a sugar both with and without a catalyst. Notice that the initial energy of reactants and the final energy of the products are unchanged by the catalyst. Slide 20 / 64 Activation energy is _____. 5 A the heat released in a reaction B the energy given off when reactants collide C generally very high for a reaction that takes place rapidly D an energy barrier between reactants and products Slide 21 / 64 6 What happens to a catalyst in a reaction? A It is unchanged. B It is incorporated into the products. C It is incorporated into the reactants. D It evaporates away.
Slide 22 / 64 7 Why does a catalyst cause a reaction to proceed faster? A Only because there are more collisions per second. B Only because collision occur with greater energy. C Only because the activation energy is lowered. There are more frequent collisions and they D are of greater energy. Slide 23 / 64 If a catalyst is used in a reaction _____. 8 A the energy of activation increases B different reaction products are obtained C the reaction rate increases D it evaporates away Slide 24 / 64 Temperature, pH, Inhibition Return to Table of Contents
Slide 25 / 64 Enzymes Have Optimal Environments Since enzymes are proteins and proteins are sensitive to their environments, enzymes are also sensitive to their environments. Factors Affecting Enzyme Activity Temperature pH Slide 26 / 64 Effect of Temperature on Enzymes In general, increasing the temperature of a system increases the reaction rate because the substrates are able to move faster and have more collisions with the active sites of the enzymes. This is true only up to certain temperatures for each type of enzyme! We call this temperature the optimal temperature. The optimal temperature is different for each type of enzyme. Slide 27 / 64 Effect of Temperature on Enzymes Past the optimal temperature, the enzyme begins to denature or lose its shape, which changes the shape of the active site.
Slide 28 / 64 Optimal Temperature and Fever Fever is the elevation of body temperature above normal (In humans 98.6 o F). Typically, fevers develop in response to bacterial or viral infection. The optimal temperature for most bacterial enzymes is less than 98 o F, so by raising body temperature above that, the immune system attempts to denature the bacteria's enzymes and stop the infection. Slide 29 / 64 Common Enzymes Laundry detergents contain enzymes that help break up and remove stains from your clothing. Why might you want to use a different laundry detergent when you wash clothes in hot water instead of in cold water? Slide 30 / 64 Effect of pH on Enzymes pH level can also cause a denaturing of the enzyme. Increasingly [H+] > [OH–] Most biological solutions have pH Acidic values between 6-8.
Slide 31 / 64 Effect of pH on Enzymes (optimal pH = 4.2) The optimal pH for most enzymes is between 6-8, but again the optimal pH is different for each type of enzyme. Slide 32 / 64 9 What is the optimal temperature for this enzyme? Slide 33 / 64 10 What is the optimal pH of this enzyme?
Slide 34 / 64 11 Which enzyme has a lower optimal temperature? Slide 35 / 64 12 At which temperature do both enzymes have an equal rate of reaction? Slide 36 / 64 13 Which description best explains the temperature effects shown in the graph? A Each enzyme will function at room temperature. B Both enzymes are inactive at the freezing point. C Each enzyme has its own optimal temperature range. D Both enzymes have the same optimal temperature range.
Slide 37 / 64 14 Based on this information which environment can you conclude as being more acidic? A Stomach B Liver Stomach Enzyme Liver Enzyme Slide 38 / 64 15 Which enzyme would you choose to use in a basic environment? A B C Slide 39 / 64 The active site of an enzyme 16 I. is the part where a substrate can fit II. can be used again and again III. is not affected by environmental factors A I only B II only C III only D I and II E I and III
Slide 40 / 64 Cofactors Sometimes enzymes need a helper to bind at the active site to make the enzyme active. These helpers are called cofactors . If the cofactors are organic molecules, then they are called coenzymes . Vitamins are a type of coenzyme. coenzyme substrate Enzyme Slide 41 / 64 Enzyme Inhibitors Certain chemicals work to stop or inhibit the enzymes. These chemicals are called enzyme inhibitors. Types of Inhibitors · Competitive Inhibitors · Noncompetitive Inhibitors click here for an animation about inhibition Slide 42 / 64 Competitive Inhibitors Competitive inhibitors are similar in shape to the Competitive inhibitor substrates. They are able to block the substrates from binding to the active site by binding to the active site themselves.
Slide 43 / 64 Competitive Inhibitors: How They Are Stopped To stop competitive inhibition, the concentration of the substrates needs to be increased so that they outnumber the inhibitors. This way, the substrates are more likely to bind to the active site before an inhibitor does. Slide 44 / 64 Noncompetitive Inhibitors: How they work Noncompetitive inhibitors bind to a separate part of the enzyme and cause the enzyme to change shape. When the enzyme changes shape, the substrate is no longer able to bind to the active site because the active site also changes shape. This type of inhibition is sometimes irreversible. Slide 45 / 64 17 Organic molecules that aid in the action of the enzyme are called ____. A products B coenzymes C substrates D helpers
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