Lesson 6. ENZYMES, THEIR STRUCTURE AND COMMON PROPERTIES. MECHANISMS OF ENZYME REACTIONS

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Task

Guidelines for performing the task

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Study the chemical nature of enzymes, their similarities and differences compared with inorganic catalysts

1. Give the definition of enzymes. Point out the evidence of their proteinic nature.

2. Compare the properties of enzymes and inorganic catalysts.

3. What is activation energy? Draw a graph that gives a thermodynamic explanation to this phenomenon.

4. Fill in the table showing the similarities and differences between enzymes and inorganic catalysts

Properties

Enzymes

Inorganic catalysts

Effect on reaction rate Effect on dynamic equilibrium Decreasing the activation energy Adsorption on the surface Formation of intermediates Substrate specificity

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Study the theory of enzymatic catalysis

Write down the main points of enzymatic catalysis, compare with inorganic catalysis

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Study the structure of enzymes

1. Characterize the structure of simple and conjugated enzymes. Explain the terms coenzyme, apoenzyme, holoenzyme, active site, allosteric site.

2. Describe the structure of the active site of simple and conjugated enzymes.

3. Can any other classes of biopolymers show catalytic activity?

4. Make a schematic representation of the structure of cholinesterase active site.

5. List amino acids that most commonly participate in the formation of the active site

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Study enzymatic specificity

1. Explain the term specificity of enzymes.

2. Give examples of enzymes with individual, group and stereochemical specificity.

3. Describe two theories of enzymatic specificity proposed by Fischer and Koshland

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Study

the mechanism of enzymatic effect

1. Recall the main theories of catalysis.

2. Write down and explain the general scheme of the enzymatic process (Fischer equation).

3. Study the mechanism of cholinesterase action

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Study the dependence of enzymatic activity on the temperature

1. Write a graph reflecting the dependence between temperature and enzyme activity.

2. Charactirize enzymatic activity at 0⁰С and at 100⁰С.

3. Give examples of thermolabile and thermostable enzymes.

4. What is the practical application of knowledge about the dependence between enzyme activity and the temperature?

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Study the effect of pH value on enzyme activity

Draw a graph of dependence between the activity of pepsin, trypsin, amylase, acid and alkaline phosphatase, and pH. 2. Point out predominant factors that explain the dependence between pH and enzymatic activity

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Study the current classification and nomenclature of enzymes

1. Describe the International classification of enzymes. What is the main principle of enzymes classification? Write down all classes and subclasses of enzymes in the form of a table.

2. Write down examples of the types of reactions catalyzed by each of the six classes of enzymes, and give their systematic names.

3. Determine the class, subclass and subsubclass for α-amylase, alkaline phosphatase, cholinesterase, monoamine oxidase

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Study the kinetics of enzyme catalyzed reactions

1. Derive mathematically the Michaelis constant, explain its physical significance.

2. Study the dependence of enzymatic reaction rate on substrate concentration:

1) write down the Michaelis-Menten equation;

2) analyze this equation;

3) draw a graph of dependence of reaction rate on the concentration of the enzyme;

4) write down the Lineweaver-Burk equation and draw its plot. What are the advantages of Lineweaver-Burk plot compared with Michaelis-Menten plot?

3. Characterize the dependence of enzymatic reaction rate on enzyme concentration and draw the appropriate plot