Chapter 16 Amino Acids, Proteins, and Enzymes - PowerPoint PPT Presentation

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Chapter 16 Amino Acids, Proteins, and Enzymes

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Chapter 16 Amino Acids, Proteins, and Enzymes 16.6 Enzymes 16.7 Enzyme Action Enzymes are Biological Catalysts Enzymes are proteins that Catalyze nearly all the ... – PowerPoint PPT presentation

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Title: Chapter 16 Amino Acids, Proteins, and Enzymes


1
Chapter 16 Amino Acids, Proteins, and Enzymes
  • 16.6 Enzymes
  • 16.7 Enzyme Action

2
Enzymes are Biological Catalysts
  • Enzymes are proteins that
  • Catalyze nearly all the chemical reactions taking
    place in the cells of the body.
  • Increase the rate of reaction by lowering the
    energy of activation.

3
Names of Enzymes
  • The name of an enzyme
  • usually ends in ase.
  • identifies the reacting substance. For example,
  • sucrase catalyzes the reaction of sucrose.
  • describes the function of the enzyme. For
    example, oxidases catalyze oxidation.
  • could be a common name, particularly for the
    digestion enzymes such as pepsin and trypsin.

4
Classification of Enzymes
  • Enzymes are classified by the reaction they
    catalyze.
  • Class Type of Reactions catalyzed
  • Oxidoreductases Oxidation-reduction
  • Transferases Transfer groups of atoms
  • Hydrolases Hydrolysis
  • Lyases Add atoms/remove atoms to or
  • from a double bond
  • Isomerases Rearrange atoms
  • Ligases Use ATP to combine small molecules

5
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.

6
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.

7
Active Site
  • The active site
  • is a region within an enzyme that fits the shape
    of the reacting molecule called a substrate.
  • contains amino acid R groups that bind the
    substrate.
  • releases products when the reaction is complete.

8
Enzyme Catalyzed Reaction
  • In an enzyme-catalyzed
  • reaction
  • a substrate attaches to the active site.
  • an enzyme-substrate (ES) complex forms.
  • reaction occurs and products are released.
  • an enzyme is used over and over.

E S ES E P
9
Lock and Key Model
  • In the lock-and-key model
  • the active site has a rigid shape.
  • an enzyme only binds substrates that exactly fit
    the active site.
  • the enzyme is analogous to a lock.
  • the substrate is the key that fits that lock.

10
Induced-fit Model
  • In the induced-fit model
  • enzyme structure is flexible, not rigid.
  • enzyme and substrate adjust the shape of the
    active site to bind substrate.
  • the range of substrate specificity increases.
  • shape changes improve catalysis during reaction.

11
Example of An Enzyme Catalyzed Reaction
12
Learning Check
  • A. The active site is
  • (1) the enzyme
  • (2) a section of the enzyme
  • (3) the substrate
  • B. In the induced fit model, the shape of the
    enzyme when substrate binds
  • (1) stays the same
  • (2) adapts to the shape of the substrate

13
Solution
  • A. The active site is
  • (2) a section of the enzyme
  • B. In the induced fit model, the shape of the
    enzyme when substrate binds
  • (2) adapts to the shape of the substrate

14
Diagnostic Enzymes
  • Diagnostic enzymes
  • determine the amount of damage in tissues.
  • that are elevated may indicate damage or disease
    in a particular organ.

15
Diagnostic Enzymes
  • Levels of enzymes CK,
  • LDH, and AST
  • are elevated following a heart attack.
  • are used to determine the severity of the attack.

16
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.

17
Isoenzymes
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