Enzyme Function and Mechanism

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Questions and Answers

What type of enzyme is involved in the transfer of functional groups from one molecule to another?

Transferases (correct)

Oxidoreductases

Hydrolases

Lyases

Which enzyme class is primarily responsible for hydrolysis reactions involving water?

Isomerases

Lyases

Ligases

Hydrolases (correct)

Which of the following enzyme classes includes reactions that lead to the formation or removal of double bonds?

Isomerases

Lyases (correct)

Transferases

Oxidoreductases

What role do oxidoreductases typically play in biochemical reactions?

Facilitating oxidation-reduction reactions Signup and view all the answers

Which enzyme class catalyzes the ligation of molecules coupled to ATP hydrolysis?

Ligases Signup and view all the answers

What is the primary function of catabolism in metabolic processes?

To break down large molecules into smaller ones, releasing energy. Signup and view all the answers

Which type of regulation involves changes in enzyme activity through the binding of molecules at sites other than the active site?

Allosteric Regulation Signup and view all the answers

Which statement about genetic regulation of metabolic pathways is true?

It determines the amount of enzymes based on gene expression. Signup and view all the answers

What is one characteristic of ATP in cellular metabolism?

It stores and releases energy for various cellular processes. Signup and view all the answers

Which statement best describes the role of compartmentalization in metabolism?

It allows for the isolation of specific metabolic processes within organelles. Signup and view all the answers

How does hormonal regulation influence metabolic pathways?

By acting as signals that regulate enzymatic activity in specific tissues. Signup and view all the answers

What happens during covalent modification of enzymes?

Enzymes' structural conformation is altered via phosphate addition or removal. Signup and view all the answers

What distinguishes autotrophs from heterotrophs?

Autotrophs fix CO2 using solar energy, while heterotrophs obtain carbon from organic molecules. Signup and view all the answers

What effect does increasing enzyme concentration generally have on reaction velocity?

It increases reaction velocity if substrate is still available. Signup and view all the answers

Which type of inhibition can decrease both Vmax and Km?

Uncompetitive inhibition Signup and view all the answers

What happens to an enzyme when the temperature exceeds its optimal point?

It becomes denatured. Signup and view all the answers

What does a lower Km value indicate about an enzyme's substrate affinity?

Higher substrate affinity. Signup and view all the answers

In the Michaelis-Menten equation, what does Vmax represent?

The maximum reaction rate achievable. Signup and view all the answers

How do reversible inhibitors affect Km in competitive inhibition?

Km increases while Vmax remains the same. Signup and view all the answers

Which factor does not affect enzyme reaction velocity?

Color of the enzyme Signup and view all the answers

What is the significance of Kcat in enzyme kinetics?

It measures the number of substrates transformed by each enzyme per unit time. Signup and view all the answers

What does a negative change in Gibbs free energy (ΔG) indicate about a reaction?

The reaction is exergonic and releases free energy. Signup and view all the answers

How is the standard Gibbs free energy change (ΔG°) different from the Gibbs free energy change (ΔG)?

ΔG° is measured under standard conditions, while ΔG is under non-standard conditions. Signup and view all the answers

What does an increase in entropy (ΔS) generally indicate within a biological system?

The system is exhibiting greater randomness or disorder. Signup and view all the answers

Which of the following reactions represents an endergonic process?

Glucose + Pi ⇌ Glucose-6-Phosphate + H2O Signup and view all the answers

In a reaction that is at equilibrium, which statement is true?

There is no net change in the concentrations of reactants and products. Signup and view all the answers

Which of the following correctly defines the term 'bioenergetics'?

The quantitative analysis of energy transformations in living organisms. Signup and view all the answers

What is the significance of standard conditions in biochemical reactions?

They allow for comparison of Gibbs free energy changes across different reactions. Signup and view all the answers

Which equation is used to calculate the change in Gibbs free energy based on equilibrium constant?

$ ΔG = -RT ln K_{eq} $ Signup and view all the answers

What role do coenzymes play in enzymatic reactions?

They carry chemical groups or electrons. Signup and view all the answers

How does competitive inhibition affect enzyme activity?

It prevents the substrate from binding to the active site. Signup and view all the answers

Which mechanism explains the change in the enzyme's active site shape upon substrate binding?

Induced fit model Signup and view all the answers

What is the primary function of cofactors in enzymatic reactions?

To stabilize enzyme structure and enhance activity Signup and view all the answers

Which of the following correctly describes a product of an enzymatic reaction?

The product is the substance produced by enzyme action. Signup and view all the answers

What occurs in an allosteric regulation?

An inhibitor or activator binds to a different site on the enzyme. Signup and view all the answers

Which statement correctly describes the specificity of enzymes?

Enzymes exhibit a high degree of specificity for their substrates. Signup and view all the answers

What is the main effect of lowering the activation energy (Ea) by enzymes?

It increases the rate of biochemical processes. Signup and view all the answers

Study Notes

Enzyme Function

Enzymes are proteins that catalyze biochemical reactions in living organisms.
Enzymes are composed of 150-300 amino acids and work at low concentrations (mM).
Enzymes increase the rate of reactions by lowering the activation energy (Ea) needed.
They have a high degree of specificity to their substrate.

Substrate and Product

The molecule an enzyme acts on is called a substrate.
The substrate binds to the active site of the enzyme and undergoes a conformational change upon binding.
The substance produced by the enzyme action is called the product.
The product is separated from the enzyme and accumulates to high levels.

Active Site

The active site is the region of the enzyme where the substrate binds.
It contains amino acids that catalyze the reaction.
Changes in the substrate lead to temporary changes in the enzyme's structure.

Coenzymes

Coenzymes are organic molecules that aid in enzymatic reactions.
They act as carriers of chemical groups or electrons and maintain the enzyme structure.

Cofactors

Cofactors are inorganic ions or molecules that enhance enzyme activity.
They help stabilize the enzyme structure and directly participate in the reaction.

Enzyme Regulation

Competitive Inhibition: The inhibitor competes with the substrate for the binding of the enzyme's active site.
Noncompetitive Inhibition: The inhibitor binds to a different part of the enzyme, changing its shape and inhibiting the reaction.
Allosteric Regulation: The inhibitor or activator binds to an allosteric site, modifying the enzyme's activity.
Feedback Inhibition: The final product of a metabolic pathway inhibits an early enzyme in the pathway.

Mechanism of Action

Lock and Key: The substrate fits precisely into the active site of the enzyme.
Induced Fit: A change in the shape of the enzyme's active site occurs as the substrate binds.
Elimination: The enzyme catalyzes the reaction by removing part of the substrate's structure.

Enzyme Classification

Oxidoreductases catalyze oxidation-reduction reactions, often involving NAD+ or NADH.
Transferases transfer functional groups from one molecule to another.
Hydrolases catalyze hydrolysis reactions, breaking bonds with the help of water.
Lyases add or remove groups from double bonds, forming or breaking double bonds.
Isomerases catalyze isomerization reactions, rearranging atoms within a molecule.
Ligases join two molecules together using ATP hydrolysis.

Enzyme Kinetics Notes

Factors affecting enzyme reaction velocity: Temperature, pH, substrate concentration, enzyme concentration, and inhibitors.
Temperature: Enzymes have an optimal temperature for activity. Increasing temperature beyond this point can denature the enzyme.
pH: Enzymes also have an optimal pH for activity. They are generally sensitive to pH changes.
Substrate Concentration: Increasing substrate concentration increases reaction rate up to a point (Vmax).
- Vmax: Maximum velocity of the reaction.
- Km: Michaelis-Menten constant, representing the substrate concentration at which the reaction rate is half of Vmax.
Enzyme Concentration: Increasing enzyme concentration increases reaction rate if substrate is still available.
Enzyme Inhibition:
- Reversible Inhibition:
  - Competitive: Inhibitor competes with substrate for the active site. Vmax remains the same, but Km increases.
  - Non-competitive: Inhibitor binds to a site other than the active site, decreasing Vmax. Km is unaffected.
  - Uncompetitive: Inhibitor binds only to the enzyme-substrate complex, decreasing both Vmax and Km.
- Irreversible Inhibition: Inhibitor permanently modifies the enzyme, reducing Vmax or completely inhibiting activity.

Michaelis-Menten Equation

$V_{0} = \frac{V_{max} [S]}{K_{m} + [S]}$

Kcat and Km

Kcat: Number of substrate molecules converted to product per enzyme molecule per unit time.
Km: Substrate concentration at which the reaction rate is half of Vmax. A lower Km indicates higher substrate affinity.
Higher Kcat = higher catalytic efficiency.
Lower Km = higher substrate affinity.

Metabolism and Regulation

Autotrophs: Utilize solar energy to fix CO2 and obtain food from producers.
Heterotrophs: Obtain carbon from complex organic molecules of other organisms, consuming food.
Metabolism: Set of chemical reactions occurring in living organisms, catalyzed by enzymes.
- Catabolism: Breakdown of large molecules into smaller molecules, releasing energy.
- Anabolism: Building of large molecules from smaller ones, requiring energy.

Regulation of Metabolic Pathways

Genetic Regulation: Regulating the synthesis of enzymes by controlling the expression of genes.
Hormonal Regulation: Hormones act as signals to regulate enzymatic activity in specific tissues or cells.
Allosteric Regulation: Regulatory molecules bind to an enzyme at a site other than the active site, altering its shape and activity.
Covalent Modification: Addition or removal of phosphate groups (phosphorylation/dephosphorylation) modify enzymes' activity.
Compartmentalization: Cellular structures isolate specific metabolic processes, controlling the localization of substrates and enzymes.

ATP (Adenosine Triphosphate)

ATP is a molecule that stores and releases energy used in many cellular processes.
The breakdown of ATP into ADP + Pi releases energy.

Biochemistry Notes

Bioenergetics: The quantitative study of energy conversions in biological systems.
Gibbs Free Energy (ΔG): Used to determine whether a reaction is spontaneous under constant temperature and pressure.
Enthalpy (ΔH): The heat content of the system.
Entropy (ΔS): The measure of disorder or randomness in the system.
Exergonic reaction: Releases free energy, spontaneous.
Endergonic reaction: Absorbs free energy, not spontaneous.
Equilibrium: The state where the forward and reverse reaction rates are equal.
Standard conditions: Standard temperature (25°C), 1 atm pressure, and 1M concentrations of reactants and products.
- ΔG° represents change in Gibbs free energy under standard conditions.
- ΔG' is the change of Gibbs free energy under slightly non-standard conditions.

Equations

ΔG = -RT ln Keq
- Where: ΔG is the change in Gibbs free energy, R is the ideal gas constant, T is the temperature in Kelvin, and Keq is the equilibrium constant.
ΔG° = ΔG°1 + ΔG°2 +...
- Summing changes in Gibbs free energy of sequential reactions.

Examples

Hydrolysis of ATP: ATP + H₂O ⇌ ADP + Pi + energy (ΔG = -30.5 kJ/mol)
Phosphorylation of glucose: Glucose + Pi ⇌ Glucose-6-Phosphate + H2O (ΔG = +13.8 kJ/mol)

Notes Summary

These notes summarize basic concepts of thermodynamics applied to enzyme-catalyzed reactions.
They explain spontaneous reactions and the importance of energy coupling for cellular mechanisms.
The notes contain many examples of reaction equations and relate the change in Gibbs free energy under various scenarios.

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Description

This quiz explores the role of enzymes in biochemical reactions, including their structure, function, and interaction with substrates. Learn about the importance of active sites and coenzymes in enhancing enzymatic activity. Test your understanding of these vital biological catalysts.