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Questions and Answers
Which of the following accurately describes the lock-and-key model of enzyme action?
Which of the following accurately describes the lock-and-key model of enzyme action?
Enzymes decrease the reaction rate by raising activation energy.
Enzymes decrease the reaction rate by raising activation energy.
False
What is the role of enzymes in biological reactions?
What is the role of enzymes in biological reactions?
Enzymes catalyze reactions by lowering the activation energy and increasing reaction rates.
The ________ model describes how enzymes can change shape to better accommodate a substrate during binding.
The ________ model describes how enzymes can change shape to better accommodate a substrate during binding.
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Match the following enzyme properties to their descriptions:
Match the following enzyme properties to their descriptions:
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How do enzymes stabilize the transition state during a reaction?
How do enzymes stabilize the transition state during a reaction?
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Once an enzyme catalyzes a reaction, it becomes permanently altered.
Once an enzyme catalyzes a reaction, it becomes permanently altered.
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What is meant by the term 'catalysis' in the context of enzyme function?
What is meant by the term 'catalysis' in the context of enzyme function?
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What is the primary role of RNA?
What is the primary role of RNA?
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DNA is single-stranded in its structure.
DNA is single-stranded in its structure.
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What are the three types of RNA and their primary functions?
What are the three types of RNA and their primary functions?
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Enzymes lower the ______ needed for chemical reactions to occur.
Enzymes lower the ______ needed for chemical reactions to occur.
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Match the types of RNA with their functions:
Match the types of RNA with their functions:
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Which statement best describes the induced-fit model of enzyme action?
Which statement best describes the induced-fit model of enzyme action?
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Enzymes are not affected by temperature and pH changes.
Enzymes are not affected by temperature and pH changes.
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What is the difference between the lock-and-key model and the induced-fit model?
What is the difference between the lock-and-key model and the induced-fit model?
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What does the substrate must do to form an enzyme-substrate complex in the lock-and-key model?
What does the substrate must do to form an enzyme-substrate complex in the lock-and-key model?
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The induced-fit model states that the enzyme's active site is rigid and unchanging.
The induced-fit model states that the enzyme's active site is rigid and unchanging.
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Name an enzyme that exemplifies the induced-fit model.
Name an enzyme that exemplifies the induced-fit model.
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In the lock-and-key model, the enzyme acts as a 'lock' and the substrate acts as the _______.
In the lock-and-key model, the enzyme acts as a 'lock' and the substrate acts as the _______.
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Which of the following statements accurately describes the role of enzymes in chemical reactions?
Which of the following statements accurately describes the role of enzymes in chemical reactions?
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Match the following enzyme concepts with their explanations:
Match the following enzyme concepts with their explanations:
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The lock-and-key model can explain the flexibility of enzymes when interacting with different substrates.
The lock-and-key model can explain the flexibility of enzymes when interacting with different substrates.
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Enzymes can increase ___________ by adjusting their active sites during the reaction process.
Enzymes can increase ___________ by adjusting their active sites during the reaction process.
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Study Notes
Mechanism of Enzyme Action
- Enzymes have an active site, a specific region where the substrate binds.
- This active site is complementary to the substrate, allowing for lock-and-key or induced fit interactions.
Lowering Activation Energy
- Enzymes lower activation energy by facilitating a favorable environment for reactions.
- This involves:
- Orienting substrates: enzymes position substrates in the optimal arrangement.
- Straining substrate bonds: enzymes put strain on bonds within the substrate making them easier to break.
- Providing an alternative reaction pathway: bypasses high-energy steps, requiring less overall energy.
- Stabilizing transition states: stabilizes the high-energy transition state of a reaction, allowing it to proceed more easily.
Catalysis and Product Release
- Once the reaction occurs, the enzyme releases the products and is ready for new substrates.
- Enzymes are not consumed during reactions, allowing them to repeat their catalytic role.
Impact of Lowering Activation Energy
- By lowering activation energy, enzymes increase the reaction rate significantly.
- This enables essential life processes like digestion, DNA replication, and cellular respiration to occur at a sufficient rate.
Lock-and-Key Model
- In the lock-and-key model, the active site of the enzyme has a specific shape that only fits a particular substrate.
- The substrate fits perfectly into the active site without any alteration in shape, forming the enzyme-substrate complex.
- Once bound, the enzyme catalyzes the reaction by lowering activation energy, allowing the substrate to be converted into the product(s).
- This model is effective for enzymes with highly specific substrate requirements, such as sucrase, which only binds sucrose.
Induced-Fit Model
- In the induced-fit model, the enzyme's active site is flexible and conforms to the substrate upon binding, creating a snug fit.
- The active site molds itself around the substrate, strengthening the interaction and positioning the substrate optimally for the reaction.
- This allows the enzyme to better stabilize the transition state, reducing activation energy and promoting the chemical reaction.
- This model is observed in enzymes such as hexokinase, which alters its shape to bind glucose tightly.
DNA & RNA Comparisons
- DNA: exists as a stable double helix, storing and protecting genetic information.
-
RNA: exists in various forms with specific functions:
- mRNA: carries instructions from DNA to ribosomes for protein synthesis.
- tRNA: delivers amino acids to ribosomes for protein assembly based on the mRNA sequence.
- rRNA: forms part of the ribosome's structure, catalyzing peptide bond formation.
Complementary Base Pairing
-
DNA:
- Adenine (A) pairs with Thymine (T) via two hydrogen bonds.
- Cytosine (C) pairs with Guanine (G) via three hydrogen bonds.
-
RNA:
- Adenine (A) pairs with Uracil (U) via two hydrogen bonds.
- Cytosine (C) pairs with Guanine (G) via three hydrogen bonds.
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Description
Explore the fascinating mechanisms of enzyme action in this quiz. Learn how enzymes facilitate reactions by lowering activation energy and stabilizing transition states. Test your understanding of active sites, substrate interactions, and the overall catalytic process.
