Enzymes and Their Properties

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Questions and Answers

What type of reaction do hydrolases primarily catalyze?

Splitting of covalent bonds with water addition (correct)

Isomerization of molecules

Formation of covalent bonds

Addition of double bonds

Which of the following is NOT a category of enzymes mentioned?

Lyases

Isomerases

Hydrolases

Oxidases (correct)

What role do ligases/synthetases play in biochemical reactions?

Aid in the addition of hydrogen ions

Form bonds with ATP cleavage (correct)

Promote isomerization

Catalyze hydrolysis reactions

What does the suffix '-ase' in enzyme nomenclature signify?

Both substrate and type of reaction Signup and view all the answers

Which subclass of isomerases is specifically mentioned in the content?

Racemases Signup and view all the answers

What is the function of proenzymes, also known as zymogens?

Act as inactive forms of enzymes Signup and view all the answers

In the enzyme nomenclature system, what does the first digit in the enzyme code (EC) signify?

Specific enzyme category Signup and view all the answers

Which of the following statements is true regarding lyases?

They allow addition to double bonds Signup and view all the answers

What role do enzymes play in chemical reactions?

They speed up chemical reactions. Signup and view all the answers

What is one of the functions of creatine kinase?

Providing metabolic energy in active muscle tissue. Signup and view all the answers

Which enzyme is known for breaking down mucus in lungs of cystic fibrosis patients?

DNase Signup and view all the answers

Which enzyme is NOT typically used in food processing as mentioned?

Amylase Signup and view all the answers

What characteristic distinguishes enzymes from other proteins?

Enzymes serve as biochemical catalysts. Signup and view all the answers

Which enzyme is commonly used as a digestive aid in pre-cooked foods?

Pepsin Signup and view all the answers

What type of substance are enzymes classified as?

Colloidal substances Signup and view all the answers

What is the function of the active site of an enzyme?

It facilitates the binding of the substrate. Signup and view all the answers

Which enzyme is used to remove protein stains in detergents?

Alcalase Signup and view all the answers

Which type of specificity refers to an enzyme acting only on one optical isomer?

Stereochemical specificity Signup and view all the answers

What is a holoenzyme?

A complete enzyme formed from an apoenzyme and a coenzyme. Signup and view all the answers

How do the electrical charges of enzymes vary with pH?

They change from negative to positive with increasing pH. Signup and view all the answers

What are coenzymes primarily characterized by?

Being required for the activity of enzymes. Signup and view all the answers

Which of the following is NOT a category of enzymes in the International Classification of Enzymes?

Hydrolases Signup and view all the answers

Which of the following describes absolute specificity in enzymes?

The enzyme catalyzes a single reaction with a single substrate. Signup and view all the answers

What role does a coenzyme play in an enzymatic reaction?

It accepts a fragment from the substrate during the reaction. Signup and view all the answers

At what temperature does maximum enzyme activity typically occur?

37°C to 40°C Signup and view all the answers

What pH range typically results in optimal enzyme activity?

5 to 9 Signup and view all the answers

What does Koshland's Induced Fit Theory suggest about the enzyme-substrate interaction?

The enzyme adjusts its structure to accommodate the substrate's shape. Signup and view all the answers

Which enzyme is represented by the EC classification 2.7.1.1?

ATP: D-hexose-6-phosphotransferase Signup and view all the answers

Which metal is NOT typically considered a cofactor for enzyme activity?

Sodium Signup and view all the answers

What effect does increasing substrate concentration have on enzyme activity?

It has no impact until a certain concentration is reached. Signup and view all the answers

How does temperature affect enzyme-catalyzed reactions?

Increasing temperature can enhance reaction rates only within a limited range. Signup and view all the answers

What is the main idea behind Fischer’s Lock and Key Theory?

The active site must pre-fit the substrate for a reaction. Signup and view all the answers

What is the role of activators in enzyme functionality?

They transform inactive enzymes into active ones Signup and view all the answers

What role do functional groups at the catalytic site of enzymes play?

They serve as acids or bases and can also act as electron donors or acceptors. Signup and view all the answers

What happens to enzyme activity when reaction products accumulate?

Enzyme activity decreases due to reversibility Signup and view all the answers

What effect do ultraviolet rays have on enzyme activity?

They exert an inhibitory effect Signup and view all the answers

Which of the following pH values is optimal for trypsin activity?

7.8 Signup and view all the answers

Which of the following statements about enzyme concentration is true?

Increased enzyme concentration increases activity until all substrates are saturated. Signup and view all the answers

What occurs when enzyme temperature exceeds 70°C?

Enzyme activity stops due to denaturation Signup and view all the answers

What does the Activation by Strain or Bond Distortion Theory propose?

Binding induces strain in the substrate, facilitating bond breaking. Signup and view all the answers

Study Notes

Enzymes

Enzymes are biochemical catalysts synthesized by living cells.
They speed up chemical reactions and facilitate continuous replacement and renewal processes in living organisms.
Enzymes regulate the rates of physiological processes, playing critical roles in health and disease.
Enzymes are colloidal substances and proteins in nature.
They can be found in crystalline form.

Properties of Enzymes

Catalytic Power: Enzymes possess immense catalytic power, meaning they can be reused for multiple catalytic reactions.
Specificity: Enzymes are highly specific in their action.
- Substrate Specificity: Each enzyme acts on a specific substance called a substrate.
- Reaction Specificity: Enzymes catalyze only a specific type of reaction.
Electrical Charges: Enzymes have electrical charges that depend on the pH of the environment.
- Positive (+) charge for enzymes with a pH greater than 7.
- Negative (-) charge for enzymes with a pH less than 7.

Components of an Enzyme

Active Site: The functional part of an enzyme where the catalytic activity occurs.
Binding Site: A portion within the active site that attracts and binds the substrate.
Catalytic Site: The area within the active site that directly facilitates the chemical reaction.

Coenzymes

Coenzymes are heat-stable, low-molecular-weight organic compounds that are required for the activity of some enzymes.
They are linked to enzymes by non-covalent bonds.
Coenzymes act as acceptors for fragments during substrate degradation.
The protein portion of an enzyme is called an apoenzyme.
When an apoenzyme combines with its coenzyme, it forms a complete enzyme called a holoenzyme.

International Classification of Enzymes

Enzymes are classified into six classes, each with subclasses and sub-subclasses, based on the type of reaction they catalyze.
Each enzyme has a unique enzyme code (EC) consisting of four digits:
- Class (First Digit): Indicates the general type of reaction.
- Subclass (Second Digit): More specific type of reaction.
- Sub-subclass (Third Digit): Further refinement of the reaction type.
- Specific Enzyme (Fourth Digit): Unique identifier for a specific enzyme.
- Example: EC 2.7.1.1 refers to hexokinase, an enzyme that catalyzes the transfer of a phosphate group from ATP to glucose.

Theories of Enzyme Activity

Lock-and-Key Theory (Fischer): The active site of the enzyme perfectly complements the shape of the substrate.
Induced Fit Theory (Koshland): The enzyme undergoes a conformational change to accommodate the substrate.
Adsorption Theory: The enzyme's surface area concentrates reactants, increasing the frequency of collisions and accelerating reactions.
Activation by Strain or Bond Distortion Theory: The enzyme distorts the bonds of the substrate, weakening them and facilitating bond breaking.
Functional Groups at the Catalytic Site Theory: Amino acid residues or metal ions at the active site act as acids, bases, nucleophiles, or electrophiles to facilitate the reaction.

Factors Affecting Enzyme Activity

Enzyme Concentration: Increasing enzyme concentration increases reaction velocity.
Substrate Concentration: Reaction velocity increases with rising substrate concentration until the enzyme is saturated.
Temperature: Increased temperature generally increases reaction velocity, but only within a narrow range. The optimal temperature for most enzymes is around 37-40°C.
pH: Most enzymes have an optimal pH range, usually between 5 and 9.
Cofactors: Cofactors, often metal ions, enhance enzyme activity.
Activators: Some enzymes require activators to become active.
Product Accumulation: The accumulation of products can inhibit enzyme activity due to the reversibility of enzyme action.
Inhibitors: Inhibitors block enzyme activity.
- Reversible Inhibition: The inhibitor binds temporarily, and enzyme activity can be restored.
- Irreversible Inhibition: The inhibitor binds permanently, permanently inactivating the enzyme.
Time: Optimum temperature and pH are effective only within specific time frames.
Light and Other Physical Agents: Light and physical agents can influence enzyme activity.
- Blue and red light can increase salivary amylase activity.
- Ultraviolet rays and radium can inhibit enzyme activity.
- Violent shaking can destroy enzyme activity.

Enzyme Nomenclature

Enzymes are named using the suffix "-ase," preceded by a term indicating:
- The substrate or substrate class
- The specific reaction catalyzed
- A combination of both
Enzymes that catalyze hydrolysis reactions may use the suffix "-lytic."
Inactive enzyme precursors (proenzymes or zymogens) use the suffix "-ogen."
The International Union of Biochemistry (IUB) uses a complex but unambiguous system for enzyme nomenclature based on reaction mechanisms.

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Description

This quiz covers the essential aspects of enzymes, their roles as biochemical catalysts, and their properties such as catalytic power and specificity. Explore how enzymes function in biological systems and their significance in health and disease. Test your understanding of these vital proteins in living organisms.