Enzyme Activity and Factors Influencing It

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Questions and Answers

What happens to an enzyme's activity when the temperature exceeds its optimum range?

The enzyme's tertiary structure remains intact.

The enzyme converts substrate into product more rapidly.

The enzyme denatures and loses its biological activity. (correct)

The enzyme becomes more active and efficient.

How does a decrease in temperature below the optimum affect enzyme activity?

The frequency of collisions between enzyme and substrate decreases. (correct)

The enzyme becomes denatured immediately.

The movement of molecules increases, enhancing interaction.

The substrate binds more effectively to the active site.

What effect does a pH level outside the enzyme's optimum have on its structure?

It generally stabilizes the ionic bonds of the enzyme.

It promotes the successful formation of the enzyme-substrate complex.

It increases the strength of hydrogen bonds in the enzyme.

It can alter the charge of amino acids critical for binding. (correct)

Which of the following statements is true regarding enzyme denaturation?

Denatured enzymes lose their ability to bind substrates permanently. Signup and view all the answers

What is the role of hydrogen ions in enzyme activity as pH changes?

They can be gained or lost, affecting enzyme charge and activity. Signup and view all the answers

What does enzyme precipitation involve?

Separation of enzymes using aqueous or ethanol solvents Signup and view all the answers

Which of the following factors does NOT affect the enzymatic activity?

Substrate shape Signup and view all the answers

Which statement correctly describes enzyme specificity?

Enzymes are highly specific for their substrates due to the conformation of the active site. Signup and view all the answers

Which condition will likely slow down the enzymatic reaction?

Low enzyme and substrate concentrations Signup and view all the answers

What is an example of a regulator of enzyme activity?

Activator molecules Signup and view all the answers

What is the significance of enzymatic catalysis in comparison to non-catalyzed reactions?

Enzyme-catalyzed reactions can increase reaction rates by factors of 1,000 to 100,000,000. Signup and view all the answers

What are the different types of enzyme specificity?

Substrate specificity, product specificity, function specificity, stereochemical specificity Signup and view all the answers

What is the primary difference between the lock-and-key model and the induced-fit model of enzyme action?

The induced-fit model suggests that substrates must alter their shape to fit the active site. Signup and view all the answers

Which analogy is used to explain the lock-and-key model?

A key fitting into a lock. Signup and view all the answers

What role does the enzyme-substrate complex play in the enzyme-catalyzed reaction?

It is an intermediate that forms before the activation energy is lowered. Signup and view all the answers

What is a limitation of the lock-and-key model?

It does not account for the flexibility of enzyme active sites. Signup and view all the answers

How does the induced-fit model enhance enzyme activity?

By changing the enzyme's active site shape upon binding. Signup and view all the answers

In both models of enzyme action, what common feature is emphasized?

Enzymes lower the activation energy of biochemical reactions. Signup and view all the answers

What is an example of a non-catalyzed reaction pathway as described in the content?

Reactant A + Reactant B ➞ Product AB. Signup and view all the answers

What explains the high specificity of enzyme activity in the lock-and-key model?

The substrate shape matches precisely with the active site shape. Signup and view all the answers

Which statement accurately describes the relationship between the enzyme and substrate in the induced-fit model?

Substrates bind causing a change in the enzyme's structure. Signup and view all the answers

What does the lock-and-key model suggest about the interaction between the enzyme and substrate?

The enzyme and substrate are complementary in structure. Signup and view all the answers

What is the primary function of protease in the body?

To break down proteins into amino acids Signup and view all the answers

Which enzyme is responsible for breaking down lactose into glucose and galactose?

Lactase Signup and view all the answers

Which of the following statements about activation energy is true?

Lower activation energy increases the number of molecules that can react. Signup and view all the answers

Which mechanism does an enzyme NOT use to accelerate chemical reactions?

Changing the temperature of the reactants Signup and view all the answers

What role does acetylcholinesterase play in the body?

It breaks down the neurotransmitter acetylcholine. Signup and view all the answers

How do enzymes alter the electrostatic structure of a substrate?

By donating or accepting protons via their amino acids. Signup and view all the answers

What does the suffix ‘-ase’ in enzyme nomenclature indicate?

The reaction which the enzyme catalyzes Signup and view all the answers

Which enzyme specifically participates in the digestion of fats?

Lipase Signup and view all the answers

In the systematic naming of enzymes, what does the number 3 in EC 3.4.11.1 represent?

The main class the enzyme belongs to Signup and view all the answers

Which class of enzymes is denoted by the number 4 in the EC classification system?

Transferases Signup and view all the answers

What does the term 'inducing strain in the substrate' refer to in enzyme catalysis?

Altering the shape of the substrate to facilitate reaction. Signup and view all the answers

Which enzyme helps convert starches into sugars?

Amylase Signup and view all the answers

What types of bonds do hydrolases primarily act upon?

Some type of bond, depending on the enzyme Signup and view all the answers

What is the optimum temperature range for human enzymes?

35°- 40°C Signup and view all the answers

What does the sub-subclass number 11 in EC 3.4.11.1 indicate?

The specific type of bond acted upon Signup and view all the answers

Which enzyme is identified by the complete code EC 3.4.11.1?

A hydrolase that hydrolyzes peptide bonds Signup and view all the answers

What characteristic is true for all enzymes within the same subclass?

They catalyze the same type of reaction Signup and view all the answers

How does temperature influence enzyme activity?

Temperature affects molecular collisions and kinetic energy Signup and view all the answers

What does the term 'amino-peptidase' in EC 3.4.11.1 refer to?

An enzyme that hydrolyzes peptide bonds at the amino end Signup and view all the answers

Study Notes

Unit Three: Enzymes

Enzymes are globular proteins with a uniquely shaped active site.
Enzymes accelerate chemical reactions by lowering activation energy.
Activation energy is the minimum energy needed for reactants to become products.
Enzymes are biological catalysts, but remain unchanged by the reaction.
All enzymes are proteins; however, not all biological catalysts are proteins (e.g., ribozymes are RNA molecules with catalytic activity).
Globular proteins have unique tertiary structures which give them a unique shape.
A catalyst speeds up a reaction, but the reaction itself is unaltered.
Enzymes are the mediators of metabolism.
Metabolism encompasses chemical and physical changes (including breakdown and synthesis) of molecules.
Enzymes accelerate bond breaking (catabolism) and bond forming (anabolism) processes to sustain life.
Enzyme-catalyzed reactions occur within the enzyme's active site (a pocket).
The active site's structure is responsible for the enzyme's specificity.
The substrate (molecule acted upon by the enzyme) binds to the active site, forming an enzyme-substrate complex.
Binding often causes a conformational change (induced fit) in the active site facilitating catalysis.
The enzyme-product complex dissociates to form enzyme and product.

Lesson Objectives

Define enzymes and activation energy.
Explain how enzymes work.
Describe the catalysis reaction of enzymes, activities, and substrates,

Nature of Enzymes

Enzymes are globular proteins with active sites.
Enzymes accelerate reactions by lowering activation energy, converting reactants to products.
Enzymes remain unchanged during reactions.
Enzymes are specific for a particular reaction and are made up of amino acids linked together by peptide bonds.
All globular proteins have unique tertiary structures which gives them a unique shape.

Enzyme Properties

Enzymes are involved in the mediation of metabolism.
Enzymes are physical and chemical properties, such as molecular weight, solubility, precipitation and denaturation.

Enzyme Denaturation

Denaturation is the unfolding of a protein's structure, losing its active site.
Denaturation occurs with high temperatures, extreme pH values or with heavy metals, causing the loss of enzyme activity.

Enzyme Properties & Functions

Enzymes, as biocatalysts, speed up reactions without themselves being consumed.
Enzyme activity depends on parameters like temperature, pH, and concentration of enzyme and substrate molecules.
Enzymes work best at optimum temperatures and pH values.
Enzymes show varying levels of activity as the temperature and pH increases or decreases from their optimum values and are likely to have decreased efficiency above or below the optimum values.
The separation of enzymes is often done via solutions (aqueous or ethanol).

Types of Enzyme Specificity

Substrate: Enzyme acts only on a particular substrate.
Group: Enzyme acts only on molecules with a specific functional group (e.g., amino, phosphate or methyl).
Bond/linkage: Enzyme acts on a particular type of chemical bond.
Optical/stereochemical: Enzyme acts only on specific steric or optical isomers.
Co-factor: Enzyme act on the substrate and co-factors.

Enzyme Classification

Enzymes are categorized into six major classes based on the type of reaction they catalyze.
Each class has subclasses, and enzymes are further divided into sub-subclasses, each enzyme has a number (e.g., EC 3.4.11.1), which indicates the class, subclass, sub-subclass and serial number for identifying.

Enzyme Kinetics

Enzyme kinetics explores the rates of chemical reactions catalyzed by enzymes and the binding affinities of substrates, inhibitors, and maximal catalytic rates.
Enzyme kinetics explains how enzymes speed up reactions by lowering the activation energy of reactants.
The rates of reactions are determined by the concentrations of enzyme and substrates.
The relationship between the rate of reaction and the concentration of substrate is presented by the Km (Michaelis constant).

Michaelis-Menten Model

This model connects the rate of enzyme-catalyzed reaction ([V1]), substrate concentration ([S]), and two constants: Vmax and Km.
Vmax is the maximum velocity/maximum rate of reaction.
Km is substrate concentration at half-maximal velocity.
Km represents the enzyme's affinity for the substrate—a lower Km indicates a higher affinity.

Effects of Inhibitor on Enzyme Kinetics

Competitive: Inhibitor binds to the active site, competing with the substrate. This increases the Km, but no effect on the Vmax.
Non-competitive: Inhibitor binds to an allosteric site, altering the enzyme's shape. This causes a decrease in Vmax but no effect on Km.
Uncompetitive: Inhibitor binds only to the enzyme-substrate complex, reducing both Vmax and Km.

Enzyme Applications and Benefits of Industrial Uses

Enzymes are widely used in food, feed, textile, papermaking, leather, cleaning products, pharmaceuticals, and other industrial settings to accelerate reactions.
Enzymes facilitate reactions at lower temperatures than traditional methods, resulting in energy savings and environmental benefits (reduced CO2 emissions).
Enzymes are also used in the improvement of feed digestion, prevention of indigestion, increasing biological availability of nutrients, and manufacturing certain medicines.
Several types of enzymes with specific functions (e.g., cellulases, amylases, lipases, proteases, DNA polymerases) are used in the various industrial and biological contexts described.

Specific Enzyme Roles

Catalase: Decomposes hydrogen peroxide into water and oxygen.
Amylase: Breaks down starch into simpler sugars.
Protease: Catabolizing protein into peptide.
Lipase: Breaks down fats into fatty acids and glycerol

Factors Affecting Enzyme Action

Temperature: Enzymes have an optimal temperature range.
pH: Enzymes have an optimal pH range.
Substrate concentration: Enzyme speeds up reactions at low to medium substrate concentrations, but the reaction rate levels off once all active sites are saturated.
Enzyme concentration: Increasing enzyme concentration will increase the reaction rate but only up to a point until the substrate becomes the limiting factor.
Activators: Substances that enhance or activate enzymatic effects in a process.
Inhibitors: Substances that decrease or inhibit enzymatic effects in a process.
End-products: Products at the end of a series of reactions that may inhibit further production via negative feedback.

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Description

This quiz explores the various factors affecting enzyme activity, including temperature, pH levels, and the concept of enzyme specificity. It also discusses the implications of enzyme denaturation and the significance of enzymatic catalysis compared to non-catalyzed reactions. Evaluate your understanding of how these variables interact within biological systems.