52 Questions
Enzymes can be grouped by function and form, similar to how tools are categorized based on their function and structure. This comparison is used to illustrate:
The broad characterization of enzymes based on the reactions they catalyze and the chemistry they conduct.
In the context of the analogy between enzymes and tools, the 'giant wrench' represents:
An unfamiliar enzyme with a potential function based on its structure.
The comparison between tools and enzymes emphasizes the need for:
A wide range of enzymes to accommodate different biochemical tasks.
The analogy between tools and enzymes highlights the importance of categorizing enzymes based on:
Their function and the reactions they catalyze.
Which of the following is a potential outcome of understanding enzyme properties?
Identification of different types of inhibitors
What can knowledge of enzyme structure help determine?
Possible reaction mechanisms
What do thermodynamic parameters such as free energy and entropy not reveal?
The speed or rate of a reaction
What is the primary function of enzymes in biological systems?
Increase the rates of reactions
What can mutations to DNA sequences potentially alter?
Enzyme function
What provides important biochemical information for elucidating enzymatic mechanisms?
The structure of an enzyme and the position of amino acid side chains in the active site
What is the role of many enzymes in transmitting and carrying out biochemical signals in the cell?
Play important roles in transmitting and carrying out biochemical signals
What do most biochemical reactions rely on for catalysis?
Enzymes
What is the primary characteristic of enzymes in biological systems?
Protein catalysts
What contributes to increasing the rates of reactions in biological systems to the point where they can be used at room temperature?
Catalysts in biological systems
What are enzymes usually in terms of their protein structure?
Globular proteins
What do enzymes contribute to in biological systems?
Increasing the rates of reactions
Which model describes the interaction of the substrate with the enzyme?
Lock and key model
What percentage of reactions involve more than one substrate and have more than one product?
Over 60%
Where does catalysis occur in an enzyme?
Active site
What is responsible for substrate binding and catalysis on the active site surface of enzymes?
Residues
How are enzymatic reactions categorized based on the type of substrate and the mechanism of action of the enzyme involved?
Into six classes
Which class of enzymatic reactions involves the transfer of functional groups between substrates?
Transferases
What are examples of subclasses within the oxidoreductases class?
Oxidases and peroxidases
Which type of enzyme has multiple catalytic subunits that interact and regulate each other?
Multimeric enzymes
What is the term for the molecules produced in enzymatically catalyzed reactions?
Products
Where is the active site usually located on an enzyme?
In a cleft, pocket, or trench on the enzyme's surface
What is the term for enzymes with two or more subunits?
Multimeric enzymes
What is the term for the reactants in enzymatically catalyzed reactions?
Substrates
What is the function of enzymes in catalyzing reactions?
Increasing rates of reaction by lowering activation energy
How is the active site of an enzyme characterized?
Specific and tight binding of the substrate
What is the relationship between enzymes and equilibrium of a reaction?
Enzymes do not alter equilibrium but allow systems to achieve equilibrium more quickly
How are rates of enzymatically catalyzed reactions derived?
From rates of chemical reactions
What defines the rate of a chemical reaction?
The change in concentration of a reactant or product over time
How can enzymatically catalyzed reactions be categorized?
Based on the type of reaction they catalyze
What determines the rate of a chemical reaction?
The concentration of the reactant and product
What is the integrated rate law used for?
Expressing product concentration as a function of time
What does the rate constant (k) relate to?
The concentration to the rate of the reaction
What does the frequency factor (A) describe?
The percentage of collisions resulting in a favorable reaction
How do enzymes increase the rate of a reaction?
By lowering the activation energy barrier and stabilizing the transition state through specific binding of the substrate to the active site
What is the main characteristic of enzymes as protein catalysts?
They increase rates of reaction by lowering activation energy
Which enzyme is classified as a phosphorus-oxygen lyase that acts on ATP?
Adenylate cyclase
Which of the following enzymes is typically found in the liver or muscle, and indicates organ damage if elevated in blood?
Lactate dehydrogenase (LDH)
What is the primary function of enzymes in biological systems?
Lower activation energy of reactions
What change in activation energy results in an astounding 106-fold change in the rate constant (k) at the same temperature?
10 kJ/mol
How do enzymes facilitate reactions?
By forming a pocket to bring groups together or pull them apart
What do elevated levels of LDH, ALT, AST, and CPK in blood indicate?
Tissue or organ damage
How are enzymes classified by the Enzyme Commission (EC)?
By their category and unique EC number
What do enzymes do as catalysts without changing thermodynamic parameters or affecting equilibrium?
Lower activation energy
What is the primary role of enzymes in blood used for medical diagnosis?
Identifying tissue or organ damage
How do enzymes increase reaction rates?
By lowering activation energy
What is the main characteristic of enzymes as protein catalysts?
Lowering activation energy
What is the function of enzymes as catalysts in biological systems?
Lower activation energy of reactions
Study Notes
Enzymatically Catalyzed Reaction and Chemical Rates
- Lysozyme is an enzyme that catalyzes the hydrolytic cleavage of carbohydrate chains in bacterial cell walls, belonging to EC classification 3, hydrolases.
- Enzymes are protein catalysts that increase rates of reaction by lowering activation energy, often being monomeric or multimeric globular proteins.
- The active site of an enzyme specifically binds the substrate, and the binding is specific and tight, excluding solvent.
- Enzymes can be categorized based on the type of reaction they catalyze, and they do not alter equilibrium but allow systems to achieve equilibrium more quickly.
- Rates of enzymatically catalyzed reactions can be derived from rates of chemical reactions and are powerful tools for describing reactions.
- The rate of a chemical reaction is defined as the change in concentration of a reactant or product over time.
- Enzymatically catalyzed reactions can be categorized based on the six types of reactions found in section 4.1.2.
- The rate of a chemical reaction is determined by the concentration of the reactant and product, and can vary linearly, quadratically, or independently.
- The integrated rate law for first, second, and zeroth-order reactions allows expressing product concentration as a function of time.
- The rate constant (k) relates the concentration to the rate and has a frequency factor (A) and an exponential term that relates the activation energy (Ea), the temperature (T), and the gas law constant (R).
- The frequency factor (A) describes the percentage of collisions that result in a favorable reaction, and the exponential term relates the activation energy, temperature, and gas law constant.
- Enzymes increase the rate of a reaction by lowering the activation energy barrier and stabilizing the transition state through specific binding of the substrate to the active site.
Enzyme Classification and Function in Medical Biochemistry
- Enzymes are classified into 6 major groups by the Enzyme Commission (EC) of the International Union of Biochemistry and Molecular Biology (IUBMB), with each enzyme having a unique EC number.
- Adenylate cyclase is an example of an enzyme classified as a lyase (Class 4) and further subclassified as a phosphorus-oxygen lyase that acts on ATP.
- Enzyme activity in blood is used in medical diagnosis, with a comprehensive metabolic panel including measurements of enzymes not typically found in blood, indicating organ damage if present.
- Lactate dehydrogenase (LDH), alanine transaminase (ALT), aspartate aminotransferase (AST), and creatine phosphokinase (CPK) are enzymes found in the liver or muscle, and their elevated levels in blood indicate damage to these organs.
- Enzymes work as catalysts by lowering the activation energy of a reaction without changing the thermodynamic parameters or affecting equilibrium.
- Catalysts increase reaction rate by lowering the energy of the transition state, which is limited by the height of the activation energy.
- Enzymes lower activation energy by forming a pocket that brings groups together or pulls them apart to form a structure similar to the transition state, promoting electron flow and constraining molecules.
- A 36 kJ/mol change in activation energy results in an astounding 106-fold change in the rate constant (k) at the same temperature.
- Enzymes facilitate reactions by binding substrates using weak forces and steric interactions to align functional groups, polarize bonds, and promote electron flow to favorably orient molecules for reactions to occur.
- Enzyme activity in blood is utilized for diagnosis, with LDH, ALT, AST, and CPK serving as markers for tissue or organ damage.
- Enzymes are classified into 6 major groups, with each enzyme having a unique EC number based on its category and further subclassifications by the Enzyme Commission (EC).
- Enzymes work as catalysts by lowering the activation energy of a reaction without changing the thermodynamic parameters or affecting equilibrium, facilitating the reaction by forming a pocket that brings groups together or pulls them apart to form a structure similar to the transition state.
Test your knowledge of enzymatically catalyzed reactions, enzyme classification, and the function of enzymes in medical biochemistry with this quiz. Explore topics such as enzyme commission classification, enzyme catalysis, reaction rates, and enzyme activity in medical diagnosis.
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