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Questions and Answers
What does a positive change in free energy (ΔG) indicate about a reaction?
What is the primary role of ATP in cellular metabolism?
Which statement is true regarding the activation energy of a reaction?
How do enzymes speed up chemical reactions?
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What happens to ATP after it donates a phosphate group during an endergonic reaction?
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What characterizes the induced fit model of enzyme action?
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What does the term phosphorylation refer to in the context of ATP?
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What does it mean when the free energy (ΔG) of a system is zero?
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Study Notes
Free Energy (G)
- Higher G indicates a more unstable system.
- Metabolic reactions involve changes in free energy.
- Exergonic reactions release energy (negative ΔG).
- Endergonic reactions require energy (positive ΔG).
- At equilibrium (ΔG=0), no work can be done.
- Energy is essential for cellular functions like mechanical work, chemical reactions, and transport.
ATP
- A nucleotide consisting of a sugar (ribose), a phosphate group, and a nitrogenous base (adenine).
- Possesses three phosphate groups attached to the ribose sugar.
- Serves as the primary energy currency in cells.
- Has a high ΔG, making it a readily usable energy source.
- Energy is released through hydrolysis, breaking off a phosphate group, forming ADP and inorganic phosphate (P₁).
- ΔG of -7.3 kcal/mol in the lab, -13 kcal/mol within the cell.
How ATP Works
- ATP hydrolysis releases inorganic phosphate, which can bind to a molecule involved in an endergonic process.
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Phosphorylation is the process of ATP transferring a phosphate group to a molecule.
- This creates a phosphorylated intermediate, providing energy to complete the reaction.
Regeneration of ATP
- ATP loses energy when it phosphorylates a molecule in an endergonic reaction, becoming ADP.
- The energy released from exergonic reactions is used to regenerate ATP from ADP and P₁.
Enzymes
- Facilitate and accelerate chemical reactions.
- Proteins that act as catalysts.
- Exhibit high specificity due to their unique three-dimensional shape.
- Lower the activation energy needed for reactions to occur.
- Remain unchanged after the reaction is complete.
Activation Energy
- The minimum amount of energy required for a chemical reaction to begin.
How Enzymes Work
- Enzymes are substrate-specific.
- Substrate refers to the molecule that binds to the enzyme.
- Only the active site of the enzyme interacts with the substrate.
- The enzyme's shape can change to better fit the substrate (induced fit).
- Once the reaction occurs, the products have a lower affinity for the active site and are released.
- The enzyme remains unchanged and ready to catalyze another identical reaction.
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Description
Explore the concepts of free energy and ATP in this quiz. Understand the differences between exergonic and endergonic reactions, and learn about the role of ATP as the energy currency in cells. Dive into how ATP hydrolysis contributes to cellular functions and energy transactions.
