Podcast
Questions and Answers
What is the primary role of a catalyst in a chemical reaction?
What is the primary role of a catalyst in a chemical reaction?
Which of the following best describes the function of enzymes?
Which of the following best describes the function of enzymes?
What distinguishes ribozymes from most other enzymes?
What distinguishes ribozymes from most other enzymes?
An enzyme that catalyzes the reaction $A + B \rightleftharpoons C + D$ will also catalyze which of the following?
An enzyme that catalyzes the reaction $A + B \rightleftharpoons C + D$ will also catalyze which of the following?
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What is meant by 'substrate specificity' of an enzyme?
What is meant by 'substrate specificity' of an enzyme?
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Which enzyme classification is involved in oxidation-reduction reactions?
Which enzyme classification is involved in oxidation-reduction reactions?
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If an enzyme is classified as EC 2.4.1.11, what does the number '4' signify?
If an enzyme is classified as EC 2.4.1.11, what does the number '4' signify?
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How does carbonic anhydrase exemplify enzyme efficiency?
How does carbonic anhydrase exemplify enzyme efficiency?
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What is the term for the protein component of an enzyme that requires a non-protein cofactor to be catalytically active?
What is the term for the protein component of an enzyme that requires a non-protein cofactor to be catalytically active?
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The activity of an enzyme is best described by which measure?
The activity of an enzyme is best described by which measure?
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Which of the following factors does not directly influence enzyme activity?
Which of the following factors does not directly influence enzyme activity?
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What does the term 'optimum temperature' refer to with respect to enzyme activity?
What does the term 'optimum temperature' refer to with respect to enzyme activity?
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How does an inhibitor affect an enzyme-catalyzed reaction?
How does an inhibitor affect an enzyme-catalyzed reaction?
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What does Km (Michaelis constant) reflect in enzyme kinetics?
What does Km (Michaelis constant) reflect in enzyme kinetics?
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A unit of enzyme activity is defined as the amount of enzyme activity that converts how much substrate in one minute?
A unit of enzyme activity is defined as the amount of enzyme activity that converts how much substrate in one minute?
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What is the major difference between reversible and irreversible enzyme inhibitors?
What is the major difference between reversible and irreversible enzyme inhibitors?
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Study Notes
Learning Objectives
- Describe enzymes and their common properties
- List enzyme classifications in correct order
- Describe factors that change enzyme activity
- Explain the relationship between Km and activity
- Explain enzyme inhibition and inhibition types
Metabolic Reactions
- Enzymes facilitate biochemical reactions by lowering activation energy
- Enzymes can catalyze anabolic (synthesis) and catabolic (breakdown) reactions
- Enzymes modify existing molecules or transport them
- Enzymes have specific roles in various metabolic pathways
Glycolysis
- Glycolysis is a metabolic pathway that converts glucose to pyruvate
- Enzymes like hexokinase (HK), phosphofructokinase (PFK), and pyruvate kinase (PK) are crucial
- Illustrated diagram showing the steps and involved enzymes
Enzyme Classification
- Enzymes are often categorized using EC numbers (Enzyme Commission numbers)
- Different types of enzymes perform different types of reactions
Activation Energy
- Activation energy is the energy needed for a reaction to start
- Enzymes lower activation energy, allowing reactions to proceed faster
- Catalysts, like enzymes, do not affect the reaction equilibrium, only speed it up
Activation Energy and Catalysts
- Catalysts speed up reactions without being consumed
- Enzymes are biocatalysts that lower activation energy required for biochemical reactions
Enzyme Structure
- Enzymes consist of an apoenzyme (protein portion), and a cofactor (non-protein portion)
- These components combine to form a holoenzyme (complete active enzyme)
- An illustration showing the structure with an active site where substrate binds
Enzyme Active Site
- The active site of an enzyme is a unique region for substrate binding
- Amino acids within the active site are precisely arranged to catalyze the reaction
- A graphic illustration of an active site with key amino acid residues
Enzyme Activity
- Enzyme activity (V) refers to the reaction rate or how quickly a substrate is converted to a product
- One unit (U) of enzyme converts one micromole (µmol) of substrate to product in one minute
- Illustrated with a graphical analogy using a speedometer
Factors Affecting Enzyme Activity
- Enzyme concentration: higher concentration leads to faster reaction
- Substrate concentration: increased substrate initially increases reaction rate, reaching saturation
- Temperature: optimal temperature exists; beyond that, enzyme denatures
- pH: specific pH levels are ideal for optimal activity
- Inhibitors: competitive or non-competitive inhibitors bind to reduce activity
Enzyme Concentration
- Reaction rate increases with increasing enzyme concentration
- Demonstrated in a graph showing reaction rate as a function of time and enzyme concentration
Substrate Concentration
- Substrate concentration affects the reaction rate, as shown in a graph
- Km (Michaelis-Menten constant) is the substrate concentration at half-maximal velocity (Vmax)
Temperature
- Enzymes have optimal temperatures for activity
- Temperature increase affects enzyme activity until denaturation
pH
- Enzymes exhibit optimal pH ranges for activity
- Different enzymes have different optimal pH values
Inhibitors
- Inhibitors decrease enzyme activity
- Reversible inhibitors bind and release, while irreversible inhibitors bind permanently and denature the enzyme
- Competitive inhibitors bind to the active site preventing substrate binding.
- Noncompetitive inhibitors bind elsewhere on the enzyme changing the enzyme's shape.
Reversible Inhibition
- Competitive, noncompetitive, and uncompetitive are types of reversible inhibition
- Graphically showing the effects of various inhibitors on enzyme activity, by affecting Km and Vmax
Enzyme Kinetics and Km
- Km is a measure of affinity between enzymes and substrates
- A higher Km implies a lower affinity, lower Km higher affinity
- Km reflects the affinity of an enzyme towards its substrate
- Illustrated using a reaction rate graph to better understand Km
Km: A Clinical Example
- Km values can be used to understand the toxicity of substances
- Alcohol dehydrogenase, an enzyme, is involved in alcohol metabolism
- Illustrated with various metabolic equations
Regulation of Enzyme Activity
- Enzyme synthesis, degradation, and modification affect enzyme activity.
- Methods such as phosphorylation, negative feedback, and compartmentalization regulate the effectiveness of enzymes.
- The location and modification of an enzyme influence its activity.
Enzyme Regulation: Phosphorylation/Dephosphorylation
- Phosphorylation or dephosphorylation modify enzyme activity.
Regulation of Enzyme Activity: Feed-Back Inhibition
- Negative feedback inhibition, where products regulate the initiating enzyme, controls reaction velocity
Regulation of Enzyme Activity: Feed-Forward Activation
- An earlier reaction activating a later reaction in a metabolic pathway
Isozymes
- Isozymes are related enzymes that catalyze the same reaction with similar but different amino acid sequences.
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Description
This quiz covers essential concepts in biochemistry related to enzymes, including their properties, classifications, and the factors influencing their activity. Additionally, it delves into glycolysis, a key metabolic pathway, highlighting the enzymes involved and their roles. Test your understanding of enzyme functions and metabolic reactions.
