Enzymes—Nature’s Chemists

Enzymes—Nature’s Chemists
Chapter 10 Enzymes—Nature’s Chemists © 2011 Pearson Education, Inc.

Chapter Outline 10.1 Enzymes and Their Substrates 10.2 Thermodynamics of Chemical Reactions 10.3 Enzymes and Catalysis 10.4 Factors That Affect Enzyme Activity © 2011 Pearson Education, Inc. Chapter 10

Introduction Enzymes are biologically active proteins that accelerate the breakdown of food that is eaten. Enzymes are biological catalysts. They accelerate reactions, but are not consumed or changed in reactions. Discussions on the production or consumption of energy, specifically heat, during chemical reactions is called thermodynamics. © 2011 Pearson Education, Inc. Chapter 10

ENZYME CHARACTERISTICS
Enzymes are proteins that catalyze chemical reactions. They speed up chemical reactions by lowering activation energies.

ENZYME CHARACTERISTICS, cont.
Enzymes are specific in the type of reactions they catalyze. Absolute specificity – acts only on one substance Relative specificity – acts on structurally related substances Stereochemical specificity – distinguishes between stereoisomers Their activity can be regulated.

CLASSIFYING AND NAMING ENZYMES
A substrate is the substance that undergoes a chemical change catalyzed by an enzyme. Enzyme names are based on the substrate or type of reaction and adding –ase ending.

CLASSIFYING AND NAMING, cont.

Learning Check Match the type of reaction with an enzyme.
1) aminase 2) dehydrogenase 3) isomerase 4) synthetase A. Converts a cis-fatty acid to a trans-fatty acid. B. Removes 2 H atoms to form double bond. C. Combines two molecules to make a new compound. D. Adds NH3.

Solution Match the type of reaction with an enzyme
1) aminase 2) dehydrogenase 3) isomerase 4) synthetase A. 3 Converts a cis-fatty acid to a trans-fatty acid. B. 2 Removes 2 H atoms to form double bond. C. 4 Combines two molecules to make a new compound. D. 1 Adds NH3.

10.1 Enzymes and Their Substrates
Enzymes are large proteins with complex, three-dimensional structures. Enzymes work in an aqueous environment in our body so that the protein chain folds such that the polar amino acids are on the surface. Consider hexokinase, an enzyme whose job is to transfer a phosphate group from the high energy molecule, adenosine triphosphate, ATP, to D-glucose. © 2011 Pearson Education, Inc. Chapter 10

10.1 Enzymes and Their Substrates, Continued
In this equation, the enzyme name is written above or below the reaction arrow. The phosphate group is represented by a P in a circle. © 2011 Pearson Education, Inc. Chapter 10

When in its proper three-dimensional shape, hexokinase has an indentation on one side of the structure. This indentation is known as the active site, and it is lined with amino acid side chains. The active site is the functional part of an enzyme where catalysis occurs. © 2011 Pearson Education, Inc. Chapter 10

Glucose, the reactant for hexokinase, fits snugly in the active site. In an enzyme reaction, the reactant is called the substrate. Enzymes have specific substrates, a property known as substrate specificity. For example, the active site of hexokinase reacts with D-glucose, but will not react with L-glucose. Enzymes are specific for one enantiomer of the substrate. © 2011 Pearson Education, Inc. Chapter 10

Some enzymes, like hexokinase, have non-protein helpers. Two categories of helpers are as follows: Cofactors are inorganic substances like magnesium ions. Coenzymes are small organic molecules derived from vitamins. Riboflavin found in the coenzyme flavin adenine dinucleotide (FAD) is a coenzyme. © 2011 Pearson Education, Inc. Chapter 10

ENZYME COFACTORS Some enzymes require a second substance present (cofactor) in order to be active. Cofactors can be a nonprotein molecule or ion. If the cofactor is an organic molecule, it is called a coenzyme. An apoenzyme is the catalytically inactive protein formed by the removal of the cofactor. Coenzymes are often derived from vitamins.

Function of Coenzymes A coenzyme prepares the active site for catalytic activity.

Water-Soluble Vitamins
Water-soluble vitamins are soluble in aqueous solutions. cofactors for many enzymes. not stored in the body. Copyright © by Pearson Education, Inc.

Fat-Soluble Vitamins Fat-soluble vitamins are A, D, E, and K.
are soluble in lipids, but not in aqueous solutions. are important in vision, bone formation, antioxidants, and blood clotting. are stored in the body.

Learning Check Identify each compound as a
1) water-soluble vitamin or 2) fat-soluble vitamin. A. Folic acid B. Retinol (vitamin A) C. Vitamin C D. Vitamin E E. Niacin

Solution Identify each compound as a
1) water-soluble vitamin or 2) fat-soluble vitamin. A. 1 Folic acid B. 2 Retinol (vitamin A) C. 1 Vitamin C D. 2 Vitamin E E. 1 Niacin

Thiamin (Vitamin B1) Thiamin was the first B vitamin identified.
is part of the coenzyme thiamin pyrophosphate (TPP), required in the decarboxylation of -keto carboxylic acids. deficiency results in beriberi (fatigue, weight loss, and nerve degeneration). Copyright © by Pearson Education, Inc.

Riboflavin (Vitamin B2)
Riboflavin is made of the sugar alcohol ribitol and flavin. part of the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). needed for good vision and healthy skin. N H 3 C 2 O D - R i b t o l

Niacin (Vitamin B3) O C H N Niacin
is part of the coenzyme nicotinamide adenine dinucleotide (NAD+) involved in oxidation-reduction reactions. deficiency can result in dermatitis, muscle fatigue, and loss of appetite. is found in meats, rice, and whole grains. N C O H Copyright © by Pearson Education, Inc.

Pantothenic Acid (Vitamin B5)
is part of coenzyme A needed for energy production, as well as glucose and cholesterol synthesis. deficiency can result in fatigue, retarded growth, cramps, and anemia. is found in salmon, meat, eggs, whole grains, and vegetables. H O C 2 N 3

Cobalamin (Vitamin B12) Cobalamin
consists of four pyrrole rings with a Co2+. is a coenzyme for enzymes that transfer methyl groups and produce red blood cells. deficiency can lead to pernicious anemia and nerve damage. Copyright © by Pearson Education, Inc.

Ascorbic Acid (Vitamin C)
is required in collagen synthesis. deficiency can lead to weakened connective tissue, slow-healing wounds, and anemia. is found in blueberries, citrus fruits, tomatoes, broccoli, red and green vegetables. O C H 2 Copyright © by Pearson Education, Inc.

Folic Acid (Folate) Folic acid (folate) consists of pyrimidine,
p-aminobenzoic acid, and glutamate. forms the coenzyme THF used in the transfer of carbon groups and the synthesis of nucleic acids. deficiency can lead to abnormal red blood cells, anemia, and poor growth. Copyright © by Pearson Education, Inc.

Vitamin A Vitamin A is obtained from meats and beta-carotenes in plants. has beta-carotenes that are converted by liver enzymes to vitamin A (retinol). H 3 C 2 O B e t a - c r o n R i l ( v m A ) Copyright © by Pearson Education, Inc.

Vitamin D Vitamin D (D3) is synthesized in skin exposed to sunlight.
regulates the absorption of phosphorus and calcium during bone growth. deficiency can result in weakened bones. sources include cod liver oil, egg yolk, and enriched milk. Copyright © by Pearson Education, Inc.

Vitamin E Vitamin E is an antioxidant in cells.
may prevent the oxidation of unsaturated fatty acids. is found in vegetable oils, whole grains, and vegetables. O C H 3

Vitamin K Vitamin K1 in plants has a saturated side chain.
Vitamin K2 in animals has a long unsaturated side chain. Vitamin K2 is needed for the synthesis of zymogens for blood clotting. n 3

Learning Check Identify the vitamin associated with each:
1) Thiamin (B1) 2) Vitamin A 3) Vitamin K 4) Vitamin D 5) Ascorbic acid A. Collagen formation B. Beriberi C. Absorption of phosphorus and calcium in bone D. Vision E. Blood clotting

Solution Identify the vitamin associated with each:
1) Thiamin (B1) 2) Vitamin A 3) Vitamin K 4) Vitamin D 5) Ascorbic acid A Collagen formation B Beriberi C Absorption of phosphorus and calcium in bone D Vision E Blood clotting

Enzyme–Substrate Models A substrate is drawn into the active site by intermolecular attractions like hydrogen bonding. Hydrogen bonding orients the substrate properly within the active site. The initial interaction of the enzyme with the substrate is called the enzyme–substrate complex (ES). This complex forms prior to catalysis. © 2011 Pearson Education, Inc. Chapter 10

There are two enzyme–substrate models: In the Lock-and-key model, the active site is thought to be a rigid, inflexible shape that is an exact complement to the shape of the substrate. The substrate fits in the active site much like a key fits in a lock. In the induced-fit model, the active site is flexible, has a shape roughly complementary to the shape of its substrate, and undergoes a conformational change, adjusting to the shape of the substrate when the substrate interacts with the enzyme. © 2011 Pearson Education, Inc. Chapter 10

10.2 Thermodynamics of Chemical Reactions
As chemical reactions occur, some bonds are formed and some are broken, and in the process, the amount of energy changes. Some reactions release energy as heat (exothermic reactions), and some absorb energy as heat (endothermic reactions). A collision of reactant molecules must occur for a chemical reaction to occur. © 2011 Pearson Education, Inc. Chapter 10

10.2 Thermodynamics of Chemical Reactions, Continued
Energy is required to cause reactant molecules to collide. Reactant molecules must be aligned properly in order for a reaction to occur. Activation energy is required to properly align reactant molecules and to cause them to collide to produce products. © 2011 Pearson Education, Inc. Chapter 10

The activation energy that must be overcome before products are formed is shown as: The heat of reaction is the difference between the energy of reactants and the energy of products. © 2011 Pearson Education, Inc. Chapter 10

In an exothermic reaction, the energy of reactants is higher than the energy of products, so heat is released. In an endothermic reaction, the energy of products is higher than the energy of reactants, so heat is absorbed. The height of the activation energy peak gives an indication of how fast the reaction proceeds. © 2011 Pearson Education, Inc. Chapter 10

Reactions with a low activation energy will proceed at a faster rate than reactions with a high activation energy. Activation energy can be lowered with a catalyst, which will cause the reaction to proceed at a faster rate. A catalyst will not affect the energy of products or reactants. © 2011 Pearson Education, Inc. Chapter 10

Consider the addition of hydrogen peroxide to a cut. The area bubbles considerably because oxygen is produced by the enzyme catalase found in blood. A high concentration of oxygen is produced at the wound site that kills germs. Without catalase, this reaction occurs very slowly. © 2011 Pearson Education, Inc. Chapter 10

10.3 Enzymes and Catalysis Enzymes lower the activation energy by forming ES complex. ES is formed through the interactions between the enzyme and substrate. Each interaction releases a small amount of energy to stabilize the complex. These interactions combine to lower the activation energy of the reaction. Some interactions that help lower the activation energy are discussed in the next several slides. © 2011 Pearson Education, Inc. Chapter 10

10.3 Enzymes and Catalysis, Continued
Proximity The active site of enzymes has a small volume. When ES forms, the active site is filled with substrate. The reacting molecules are in close proximity to each other, and the closer they are the more likely a reaction will occur. Amino acid side chains in the active site are used to facilitate the reaction. © 2011 Pearson Education, Inc. Chapter 10

Orientation In the active site, substrate molecules are held at the appropriate distance and in correct alignment to each other for the reaction to occur. Amino acid side chains in the active site create interactions that orient the substrates. This lowers the activation energy needed for the reaction to occur. © 2011 Pearson Education, Inc. Chapter 10

Bond Energy When an enzyme interacts with substrate to form ES, the bonds of the substrate molecule are weakened (strained). Strained bonds in the substrate means that the reaction will proceed more rapidly because the activation energy is lowered by this effect. © 2011 Pearson Education, Inc. Chapter 10

Consider the hexokinase reaction that catalyzes glucose to glucose-6-phosphate. Mg2+ (a coenzyme) holds ATP in one area of the active site and glucose interacts with another area. Amino acid side chains in the active site form multiple hydrogen bonds with glucose, which stabilizes ES and lowers the activation energy. © 2011 Pearson Education, Inc. Chapter 10

A conformational change in the enzyme occurs when glucose enters the active site. ATP is in close proximity to the glucose and is in proper orientation for the reaction. Glucose-6-phosphate is formed along with ADP. The enzyme is less attracted to the products, so the lobes of the enzyme move apart and the products are released. © 2011 Pearson Education, Inc. Chapter 10

© 2011 Pearson Education, Inc.
Chapter 10

10.4 Factors That Affect Enzyme Activity
If allowed to sit untouched, the flesh of sliced apples will turn brown by a process known as oxidation, caused by an enzyme. If lemon juice is sprinkled on the sliced apple, the vitamin C in the lemon juice will inhibit the formation of this brown color by changing the pH of the environment of the enzyme. Enzyme reactions are affected by reaction conditions such as substrate concentration, pH, temperature, and the presence of inhibitors. © 2011 Pearson Education, Inc. Chapter 10

ENZYME ACTIVITY Rate at which an enzyme catalyzes a reaction.
Turnover number – number of substrate molecules acted on by one enzyme molecule per minute Enzyme international unit – quantity of enzyme that catalyzes the conversion of 1 µmol of substrate per minute

10.4 Factors That Affect Enzyme Activity, Continued
Substrate Concentration Recall that the first step in an enzyme-catalyzed reaction is the formation of ES. At a constant concentration of enzyme, an increase in substrate concentration will cause an increase in the enzyme activity up to the point where the enzyme becomes saturated with substrate. © 2011 Pearson Education, Inc. Chapter 10

FACTORS AFFECTING ACTIVITY
Enzyme concentration – the more enzyme present, the faster substrate reacts

Substrate Concentration
As substrate concentration increases, the rate of reaction increases (at constant enzyme concentration). the enzyme eventually becomes saturated, giving maximum activity.

pH When the enzyme environment is changed by pH, its tertiary structure is disrupted, altering the active site and causing the enzyme’s activity to decrease. Enzymes are most active at a pH known as their optimum pH. At optimum pH, the enzyme maintains its tertiary structure and its active site. © 2011 Pearson Education, Inc. Chapter 10

pH and Enzyme Action Enzymes are most active at optimum pH.
contain R groups of amino acids with proper charges at optimum pH. lose activity in low or high pH as tertiary structure is disrupted.

Optimum pH Values Enzymes in the body have an optimum pH of about 7.4.
certain organs operate at lower and higher optimum pH values. Changes in pH will also affect the nature of the amino acid side chains in the active site.

Temperature Enzymes have an optimum temperature at which they are most active. The optimum temperature for most human enzymes is normal body temperature, 37 oC. Above optimum temperature, enzymes lose activity due to disruption of intermolecular forces stabilizing the tertiary structure. © 2011 Pearson Education, Inc. Chapter 10

At high temperatures, enzymes denature, which modifies the active site. At low temperatures, enzyme activity is low due to a lack of energy for the reaction to occur. Food is stored in a refrigerator or freezer to slow spoilage brought on by enzymes. Boiling contaminated water will destroy enzymes in bacteria that are present in the water. © 2011 Pearson Education, Inc. Chapter 10

Temperature and Enzyme Action
Enzymes are most active at an optimum temperature (usually 37 °C in humans). show little activity at low temperatures. lose activity at high temperatures as denaturation occurs.

Learning Check Sucrase has an optimum temperature of 37 °C and an optimum pH of Determine the effect of the following on its rate of reaction. 1) no change ) increase 3) decrease A. Increasing the concentration of sucrose B. Changing the pH to 4 C. Running the reaction at 70 °C

Solution Sucrase has an optimum temperature of 37 °C and an optimum pH of Determine the effect of the following on its rate of reaction. 1) no change ) increase 3) decrease A Increasing the concentration of sucrase B Changing the pH to 4 C Running the reaction at 70 °C

Inhibitors Inhibitors are types of molecules that will cause enzymes to lose activity. Enzyme inhibitors prevent the active site from interacting with substrate to form ES. Some inhibitors cause temporary loss of activity, while others cause permanent loss of activity. © 2011 Pearson Education, Inc. Chapter 10

Reversible inhibition occurs when the inhibitor causes a temporary loss of activity. However, activity is regained if the inhibitor is removed. Reversible inhibitors can be competitive or noncompetitive. Competitive inhibitors are molecules that compete with a substrate for the active site, and have a structure similar to the substrate. © 2011 Pearson Education, Inc. Chapter 10

An example of a medical therapy that involves a competitive inhibitor involves liver alcohol dehydrogenase (LAD). This enzyme oxidizes ethanol, the alcohol found in alcoholic beverages. This enzyme will also react with ethylene glycol and methanol, which are found in antifreeze, and will compete with ethanol for the active site. If a pet is poisoned by drinking antifreeze, a slow intravenous infusion of ethanol is administrated. © 2011 Pearson Education, Inc. Chapter 10

Administration of ethanol slows the production of the toxic metabolites of ethylene glycol and methanol, giving the kidneys time to eliminate these two substrates. Noncompetitive inhibitors do not resemble the substrate. They do not compete for the enzyme’s active site. Noncompetitive inhibitors bind at a site on the enzyme that is usually remote to the active site. © 2011 Pearson Education, Inc. Chapter 10

When a noncompetitive inhibitor binds to an enzyme, it causes a conformational change in the enzyme. This change in shape causes the active site to no longer interact with the substrate. As long as this type of inhibitor is bound to the enzyme, it will no longer function effectively. © 2011 Pearson Education, Inc. Chapter 10

Inhibitions caused by competitive and noncompetitive inhibitors can be reversed. Inhibition by competitive inhibitors can be reversed by adding more substrate. The higher the concentration of substrate, the more likely it will overcome the competition for the active site. Adding more substrate with noncompetitive inhibitors has no effect on overcoming inhibition. © 2011 Pearson Education, Inc. Chapter 10

Reversing a noncompetitive inhibitor requires a special chemical reagent to remove the inhibitor and restore catalytic activity. An irreversible inhibitor forms a covalent bond with an amino acid side chain in the enzyme’s active site. Irreversible inhibition causes the substrate to be excluded from the active site. Irreversible inhibition is a permanent inhibition. © 2011 Pearson Education, Inc. Chapter 10

Antibiotics Inhibit Bacterial Enzymes Enzyme inhibitors are used to fight bacterial infections. Penicillin is an example of an irreversible inhibitor. It binds to the enzyme that bacteria use to synthesize cell walls, and slows the growth of cell walls. Without a cell wall, bacteria cannot survive and the infection stops. © 2011 Pearson Education, Inc. Chapter 10

ENZYME INHIBITION Inhibitors decrease enzyme activity.
Irreversible inhibitors covalently bond with the enzyme and render it inactive. Many poisons are irreversible inhibitors. Examples: CN-, Hg2+, Pb2+ Some antibiotics are irreversible inhibitors.

INHIBITION, cont. Reversible inhibitors reversibly bind with enzymes.
Competitive reversible inhibitors compete with substrate for binding at active site. Action can be reversed by increasing substrate concentration (LeChâtelier’s principle).

INHIBITION, cont. Noncompetitive reversible inhibitors bind to the enzyme at a location other than the active site. Substrate concentration doesn’t affect inhibitor action.

Competitive Inhibition
A competitive inhibitor has a structure that is similar to that of the substrate. competes with the substrate for the active site. has its effect reversed by increasing substrate concentration.

Noncompetitive Inhibition
A noncompetitive inhibitor has a structure that is much different than the substrate. distorts the shape of the enzyme, which alters the shape of the active site. prevents the binding of the substrate. cannot have its effect reversed by adding more substrate. Copyright © by Pearson Education, Inc.

Learning Check Identify each description as an inhibitor that is
1) competitive or 2) noncompetitive. A. Increasing substrate reverses inhibition. B. Binds to enzyme surface, but not to the active site. C. Structure is similar to substrate. D. Inhibition is not reversed by adding more substrate.

Solution Identify each description as an inhibitor that is
1) competitive or 2) noncompetitive. A. 1 Increasing substrate reverses inhibition. B. 2 Binds to enzyme surface, but not to the active site. C. 1 Structure is similar to substrate. D. 2 Inhibition is not reversed by adding more substrate.

1. Activation of zymogens – an inactive precursor of an enzyme
ENZYME REGULATION 1. Activation of zymogens – an inactive precursor of an enzyme Some enzymes are stored as inactive zymogens. Released when needed and activated at the location where the reaction occurs.

REGULATION, cont. 2. Allosteric regulation – allosteric enzyme activity is altered by the binding of a modulator Modulators can increase allosteric enzyme activity (activator) or decrease it (inhibitor). Feedback inhibition is an example of a modulator decreasing the activity of an allosteric enzyme.

REGULATION, cont. 3. Enzyme Induction – the synthesis of an enzyme in response to a cellular need This is an example of genetic control. Synthesis of -galactosidase is an example of enzyme induction.

MEDICAL APPLICATIONS Changes in blood serum concentrations of specific enzymes can be used to detect cell damage or uncontrolled growth (cancer). The measurement of enzyme concentrations in blood serum has become a major diagnostic tool, particularly in diagnosing diseases of the heart, liver, pancreas, prostate, and bones.

Diagnostic Enzymes Diagnostic enzymes
determine the amount of damage in tissues. that are elevated may indicate damage or disease in a particular organ.

Copyright © 2009 by Pearson Education, Inc.
Diagnostic Enzymes Levels of enzymes CK, LDH, and AST are elevated following a heart attack. are used to determine the severity of the attack. Copyright © by Pearson Education, Inc.

MEDICAL APPLICATIONS, cont.

MEDICAL APPLICATIONS, cont.
Isozymes are slightly different forms of the same enzyme produced by different tissues. Serum levels of isozymes can be used in the diagnosis of a wide range of diseases.

Isoenzymes Isoenzymes
catalyze the same reaction in different tissues in the body. can be used to identify the organ or tissue involved in damage or disease. such as lactate dehydrogenase (LDH), which converts lactate to pyruvate, consists of five isoenzymes. such as LDH have one form more prevalent in heart muscle and another form in skeletal muscle and liver.

Chapter Summary 10.1 Enzymes and Their Substrates
Enzymes are large, globular proteins that serve as biological catalysts. The functional part of an enzyme is the active site. Substrates are the reactants for an enzyme reaction, and they bind to the active site to form ES. © 2011 Pearson Education, Inc. Chapter 10

Chapter Summary, Continued
10.1 Enzymes and Their Substrates, Continued Enzymes are specific for one substrate that will bind to the active site and react. Two theories, lock-and-key and induced-fit, explain how an enzyme interacts with its substrate to form ES. © 2011 Pearson Education, Inc. Chapter 10

10.2 Thermodynamics of Chemical Reactions Thermodynamics is a study of the energy changes that occur during a chemical reaction. Activation energy is the energy required to start a reaction, and plays a role in the rate of reaction. The lower the activation energy, the faster the rate of reaction. Heat of reaction is a measure of the production or consumption of energy in a reaction. © 2011 Pearson Education, Inc. Chapter 10

10.2 Thermodynamics of Chemical Reactions, Continued An exothermic reaction releases heat to its environment. An endothermic reaction absorbs heat from its environment. Catalysts lower the activation energy causing an increase in the rate of reaction. Enzymes form ES before catalysis, which causes a lowering of the activation energy. © 2011 Pearson Education, Inc. Chapter 10

10.3 Enzymes and Catalysis Formation of the ES complex lowers the activation energy for a catalyzed reaction. In the active site, atoms are brought close together and aligned with amino acid side chains. © 2011 Pearson Education, Inc. Chapter 10

10.3 Enzymes and Catalysis, Continued The active site also aligns the reactants with the optimal orientation for a reaction to occur. The interaction of substrate with the active site weakens bonds between atoms in the substrate so the reaction can form products easier. © 2011 Pearson Education, Inc. Chapter 10

10.4 Factors That Affect Enzyme Activity Factors such as pH, temperature, substrate concentration, and the presence of inhibitors can affect the activity of an enzyme. An increase in substrate concentration increases the rate of an enzyme-catalyzed reaction. When substrate concentration is increased, the active site becomes saturated with substrate. © 2011 Pearson Education, Inc. Chapter 10

10.4 Factors That Affect Enzyme Activity, Continued When the active site is saturated, the enzyme is operating at steady state. Enzymes have an optimum pH and temperature at which they function best. Inhibitors decrease or eliminate an enzyme’s catalytic abilities. © 2011 Pearson Education, Inc. Chapter 10

10.4 Factors That Affect Enzyme Activity, Continued The effect of inhibitors can be reversible or irreversible. Reversible inhibitors can be competitive inhibitors, which compete with the substrate for the active site. Reversible inhibitors can also be noncompetitive, which bind to a site on the enzyme other than the active site, and causes a conformational change in the enzyme. © 2011 Pearson Education, Inc. Chapter 10

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