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Enzyme Reading (H) Enzyme Reading (H) Enzyme Reading (H) To start a chemical reaction, it is first necessary to weaken chemical bonds in the reactant molecules. This activation process requires that the molecules absorb energy. For example, to burn a candle you need to provide the initial energy with a match. This "start-up" energy is called activation energy because it activates the reactants and triggers a chemical reaction. To start a chemical reaction, it is first necessary to weaken chemical bonds in the reactant molecules. This activation process requires that the molecules absorb energy. For example, to burn a candle you need to provide the initial energy with a match. This "start-up" energy is called activation energy because it activates the reactants and triggers a chemical reaction. To start a chemical reaction, it is first necessary to weaken chemical bonds in the reactant molecules. This activation process requires that the molecules absorb energy. For example, to burn a candle you need to provide the initial energy with a match. This "start-up" energy is called activation energy because it activates the reactants and triggers a chemical reaction. Cellular reactions depend on the assistance of catalysts, compounds that speed up chemical reactions. The main catalysts of chemical reactions in organisms are specialized proteins called enzymes. Cellular reactions depend on the assistance of catalysts, compounds that speed up chemical reactions. The main catalysts of chemical reactions in organisms are specialized proteins called enzymes. Cellular reactions depend on the assistance of catalysts, compounds that speed up chemical reactions. The main catalysts of chemical reactions in organisms are specialized proteins called enzymes. Enzymes provide a way for reactions to occur at the cell's normal temperature. An enzyme doesn't supply activation energy to the reacting molecules, but instead lowers the energy requirement barrier so that the reaction can proceed at normal cell temperatures. Enzymes provide a way for reactions to occur at the cell's normal temperature. An enzyme doesn't supply activation energy to the reacting molecules, but instead lowers the energy requirement barrier so that the reaction can proceed at normal cell temperatures. Enzymes provide a way for reactions to occur at the cell's normal temperature. An enzyme doesn't supply activation energy to the reacting molecules, but instead lowers the energy requirement barrier so that the reaction can proceed at normal cell temperatures. How Enzymes Work Just how does an enzyme catalyze only one type of reaction? The reason is that the shape of each enzyme fits the shape of only particular reactant molecules. A specific reactant acted upon by an enzyme is called the enzyme's substrate. The substrate fits into a particular region of the enzyme, called the active site. How Enzymes Work Just how does an enzyme catalyze only one type of reaction? The reason is that the shape of each enzyme fits the shape of only particular reactant molecules. A specific reactant acted upon by an enzyme is called the enzyme's substrate. The substrate fits into a particular region of the enzyme, called the active site. How Enzymes Work Just how does an enzyme catalyze only one type of reaction? The reason is that the shape of each enzyme fits the shape of only particular reactant molecules. A specific reactant acted upon by an enzyme is called the enzyme's substrate. The substrate fits into a particular region of the enzyme, called the active site. Figure on the back of this paper follows the action of the enzyme sucrase, which catalyzes the hydrolysis of sucrose (the substrate). (Most enzymes have names that end in -ase.) Sucrose is slightly distorted as it enters the active site. The weakened bond reacts with water. The result is two products: a glucose molecule and a Figure on the back of this paper follows the action of the enzyme sucrase, which catalyzes the hydrolysis of sucrose (the substrate). (Most enzymes have names that end in -ase.) Sucrose is slightly distorted as it enters the active site. The weakened bond reacts with water. The result is two products: a glucose molecule and a Figure on the back of this paper follows the action of the enzyme sucrase, which catalyzes the hydrolysis of sucrose (the substrate). (Most enzymes have names that end in -ase.) Sucrose is slightly distorted as it enters the active site. The weakened bond reacts with water. The result is two products: a glucose molecule and a fructose molecule. Once these products are released, the enzyme's active site is ready to accept another molecule of sucrose. In fact, this recycling ability is a key characteristic of enzymes. fructose molecule. Once these products are released, the enzyme's active site is ready to accept another molecule of sucrose. In fact, this recycling ability is a key characteristic of enzymes. fructose molecule. Once these products are released, the enzyme's active site is ready to accept another molecule of sucrose. In fact, this recycling ability is a key characteristic of enzymes. A substrate binds to an enzyme at an active site. The enzyme-substrate interaction lowers the activation energy required for the reaction to proceed. In this example, water is added to the weakened bond in sucrose, breaking sucrose into glucose and fructose. A substrate binds to an enzyme at an active site. The enzyme-substrate interaction lowers the activation energy required for the reaction to proceed. In this example, water is added to the weakened bond in sucrose, breaking sucrose into glucose and fructose. A substrate binds to an enzyme at an active site. The enzyme-substrate interaction lowers the activation energy required for the reaction to proceed. In this example, water is added to the weakened bond in sucrose, breaking sucrose into glucose and fructose. As with any other protein, an enzyme's structure and shape are essential to its function. And like other proteins, an enzyme's shape is sensitive to changes in its surrounding environment. Therefore, factors such as pH and temperature can greatly affect how well an enzyme works or if it can work at all. This is one reason why cells (and hence organisms) can only survive and function within certain ranges of conditions. As with any other protein, an enzyme's structure and shape are essential to its function. And like other proteins, an enzyme's shape is sensitive to changes in its surrounding environment. Therefore, factors such as pH and temperature can greatly affect how well an enzyme works or if it can work at all. This is one reason why cells (and hence organisms) can only survive and function within certain ranges of conditions. As with any other protein, an enzyme's structure and shape are essential to its function. And like other proteins, an enzyme's shape is sensitive to changes in its surrounding environment. Therefore, factors such as pH and temperature can greatly affect how well an enzyme works or if it can work at all. This is one reason why cells (and hence organisms) can only survive and function within certain ranges of conditions. Worksheet for Enzyme Worksheet for Enzyme Worksheet for Enzyme 1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy? 2. Describe how a substrate interacts with an enzyme. 1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy? 2. Describe how a substrate interacts with an enzyme. 1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy? 2. Describe how a substrate interacts with an enzyme. Step 1. 1. Molecule C is a large protein (or several proteins together) that we call an ________________. 2. Molecules A and B are called substrate, and are usually _______________ or building blocks of larger macromolecules. 3. Which of the four major biological macromolecules is C made of? Step 2. 1. Is molecule C breaking apart (decomposing) or building (synthesizing) a macromolecule? 2. If a solution is too acidic or basic, molecule C can ________________ or change it shape so that A and B will no longer fit. Step 1. 1. Molecule C is a large protein (or several proteins together) that we call an ________________. 2. Molecules A and B are called substrate, and are usually _______________ or building blocks of larger macromolecules. 3. Which of the four major biological macromolecules is C made of? Step 2. 1. Is molecule C breaking apart (decomposing) or building (synthesizing) a macromolecule? 2. If a solution is too acidic or basic, molecule C can ________________ or change it shape so that A and B will no longer fit. Step 1. 1. Molecule C is a large protein (or several proteins together) that we call an ________________. 2. Molecules A and B are called substrate, and are usually _______________ or building blocks of larger macromolecules. 3. Which of the four major biological macromolecules is C made of? Step 2. 1. Is molecule C breaking apart (decomposing) or building (synthesizing) a macromolecule? 2. If a solution is too acidic or basic, molecule C can ________________ or change it shape so that A and B will no longer fit. Step 3. 1. What will happen to molecule C now that the reaction is complete? 2. What are two things that affect how fast molecule C works? 3. Molecule D is made of building blocks represented by A and B. If D represents a polysaccharide, A and B would represent ___________________. Step 3. 1. What will happen to molecule C now that the reaction is complete? 2. What are two things that affect how fast molecule C works? 3. Molecule D is made of building blocks represented by A and B. If D represents a polysaccharide, A and B would represent ___________________. Step 3. 1. What will happen to molecule C now that the reaction is complete? 2. What are two things that affect how fast molecule C works? 3. Molecule D is made of building blocks represented by A and B. If D represents a polysaccharide, A and B would represent ___________________. Now go back to your picture (front) and label the substrate(s), product(s), enzyme, and active site. Now go back to your picture (front) and label the substrate(s), product(s), enzyme, and active site. Now go back to your picture (front) and label the substrate(s), product(s), enzyme, and active site. Analyzing Graphs Use the graph to answer the questions below. a. At which temperature does enzyme A perform best? Enzyme B? b. Knowing that one of these enzymes is found in humans and the other in thermophilic (heat-loving) bacteria, hypothesize which enzyme came from which organism. c. Propose a hypothesis that explains why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40°C. Analyzing Graphs Use the graph to answer the questions below. a. At which temperature does enzyme A perform best? Enzyme B? b. Knowing that one of these enzymes is found in humans and the other in thermophilic (heat-loving) bacteria, hypothesize which enzyme came from which organism. c. Propose a hypothesis that explains why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40°C. Analyzing Graphs Use the graph to answer the questions below. a. At which temperature does enzyme A perform best? Enzyme B? b. Knowing that one of these enzymes is found in humans and the other in thermophilic (heat-loving) bacteria, hypothesize which enzyme came from which organism. c. Propose a hypothesis that explains why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40°C.