Enzyme Classes and Functions

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Questions and Answers

Which component is NOT part of the catalytic triad in serine proteases?

  • Aspartic Acid
  • Histidine
  • Serine
  • Glutamic Acid (correct)

What defines the substrate specificity of chymotrypsin?

  • The presence of a serine residue
  • The structure of its catalytic triad
  • The complementary binding pockets for aromatic amino acids (correct)
  • The presence of basic amino acids

In the context of serine proteases, what does the term 'hydrolyze' refer to?

  • Forming peptide bonds
  • Modifying amino acid sequences
  • Cleaving peptide bonds (correct)
  • Synthesis of proteins

Which amino acids does chymotrypsin specifically target for cleavage?

<p>Phenylalanine, Tryptophan, Tyrosine (A)</p> Signup and view all the answers

Which of the following statements about serine proteases is FALSE?

<p>Their structure is identical across different enzymes. (B)</p> Signup and view all the answers

What remains unchanged after chymotrypsin cleaves a peptide bond?

<p>The enzyme (B)</p> Signup and view all the answers

What residues are consistently assigned the numbers His57, Asp102, and Ser in serine proteases?

<p>Catalytic residues of the active site (B)</p> Signup and view all the answers

Which class of enzyme is responsible for the reaction D-Glucose + ATP → D-Glucose-6-phosphate + ADP?

<p>Transferases (B)</p> Signup and view all the answers

What type of reaction is catalyzed by carboxypeptidase A?

<p>Peptide bond cleavage (B)</p> Signup and view all the answers

In the enzyme-catalyzed reaction involving cleavage of a bond, what is the role of Glu (E 270)?

<p>It performs acid-base catalysis. (C)</p> Signup and view all the answers

What type of enzyme is responsible for the reaction Maleate → Fumarate?

<p>Lyases (B)</p> Signup and view all the answers

Which of the following enzymes catalyzes a reaction involving carboxylation?

<p>Pyruvate carboxylase (A)</p> Signup and view all the answers

What type of interaction does Arg (R 145) primarily facilitate in catalysis?

<p>Charge-charge interaction (C)</p> Signup and view all the answers

Which of the following accurately describes the role of ligases?

<p>They catalyze the joining of two molecules with the use of ATP. (D)</p> Signup and view all the answers

What is the primary function of the Zn2+ ion in the enzyme's active site?

<p>It facilitates electron transfer. (A)</p> Signup and view all the answers

Flashcards

Enzyme classes

Enzymes are categorized into six major classes based on the type of reaction they catalyze.

Oxidoreductases

Enzymes that catalyze oxidation-reduction reactions, often involving electron transfer.

Transferases

Enzymes that catalyze the transfer of a functional group from one molecule to another.

Hydrolases

Enzymes that catalyze the hydrolysis of bonds using water.

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Lyases

Enzymes that catalyze the cleavage of bonds by means other than hydrolysis or oxidation.

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Isomerases

Enzymes that catalyze the interconversion of isomers.

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Ligases

Enzymes that catalyze the joining of two molecules using ATP.

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Acid-base catalysis (Glu 270)

Amino acid Glu acting as a catalyst in a reaction through transferring a proton.

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Serine Proteases

Hydrolyze peptide bonds using a catalytic triad (serine, histidine, aspartate).

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Catalytic Triad

A group of three amino acids (serine, histidine, and aspartate) crucial for serine protease activity.

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Chymotrypsin's Substrate

A peptide chain containing aromatic amino acids (phenylalanine, tryptophan, or tyrosine).

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Chymotrypsin's function

Cleaves peptide bonds next to aromatic amino acids (Phe, Trp, Tyr).

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Substrate Specificity

Chymotrypsin's ability to bind and cleave peptide bonds near specific amino acids.

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Enzyme

Biological catalyst that speeds up chemical reactions.

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Study Notes

Enzymes Fall into 6 Major Classes by Function

  • Enzymes are classified into six major classes based on the type of reaction they catalyze.
  • Each class catalyzes a specific type of reaction.
  • The classes are oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.

Examples of Enzyme Classes

  • Oxidoreductases: Catalyze oxidation-reduction reactions.
    • Example: Alcohol dehydrogenase (oxidation with NAD).
  • Transferases: Catalyze the transfer of a functional group from one molecule to another.
    • Example: Hexokinase (phosphorylation).
  • Hydrolases: Catalyze the hydrolysis of a chemical bond.
    • Example: Carboxypeptidase A (peptide bond cleavage).
  • Lyases: Catalyze the cleavage of a chemical bond by elimination, leaving a double bond or adding a group to a double bond.
    • Example: Pyruvate decarboxylase (decarboxylation).
  • Isomerases: Catalyze the isomerization of molecules.
    • Example: Malate isomerase (cis-trans isomerization).
  • Ligases: Catalyze the joining of two molecules by the formation of a new bond.
    • Example: Pyruvate carboxylase (carboxylation).

What Types of Catalysis Can You Identify?

  • Glu (E270) in Catalysis: Glu (E270) plays a role in acid-base catalysis.
  • Arg (R145) in Catalysis: Arg (R145) is involved in charge-charge interactions in catalysis.

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