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Questions and Answers
What primary role do enzymes play in biological systems?
What primary role do enzymes play in biological systems?
- They serve solely as energy sources.
- They increase the rate of chemical reactions. (correct)
- They facilitate the transportation of ions across membranes.
- They act as structural components in cell membranes.
Which of the following best describes enzymes?
Which of the following best describes enzymes?
- Enzymes are primarily carbohydrates.
- Enzymes can only catalyze reactions involving proteins.
- Enzymes are a type of protein that can act as catalysts. (correct)
- Enzymes are nucleic acids that increase reaction rates.
In the context of enzymatic reactions, what does 'exergonic' mean?
In the context of enzymatic reactions, what does 'exergonic' mean?
- Reactions that require an increase in temperature to proceed.
- Reactions that release energy spontaneously. (correct)
- Reactions that occur at an extremely slow rate.
- Reactions that absorb energy.
Which macromolecule, besides proteins, is mentioned as having catalytic properties?
Which macromolecule, besides proteins, is mentioned as having catalytic properties?
What is the significance of reaction rate in biological processes?
What is the significance of reaction rate in biological processes?
What factor is essential for enzymes to perform their catalytic function?
What factor is essential for enzymes to perform their catalytic function?
Flashcards
What are enzymes?
What are enzymes?
Enzymes are biological catalysts that accelerate chemical reactions in living organisms.
What does it mean for a reaction to be spontaneous?
What does it mean for a reaction to be spontaneous?
A spontaneous reaction is one that will favor the formation of products over time. However, spontaneity doesn't guarantee a fast reaction.
How do enzymes affect reaction rates?
How do enzymes affect reaction rates?
Enzymes increase the rate of chemical reactions. They don't change the final equilibrium, but they make the reaction reach equilibrium faster.
What is activation energy?
What is activation energy?
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How do enzymes work?
How do enzymes work?
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How do enzymes play a role in protein digestion?
How do enzymes play a role in protein digestion?
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Study Notes
Enzymes: Catalysts
- Enzymes are proteins that act as biological catalysts, increasing reaction rates for biochemical processes.
- Unlike other catalysts, many enzymes are proteins.
- They speed up reactions by lowering the activation energy (Ea).
- Small Ea values correspond to fast reactions.
- Large Ea values correspond to slow reactions.
Enzyme Activity
- Enzymes increase reaction rates by decreasing activation energy.
- Enzymes don't change the overall thermodynamics of a reaction (like the change in free energy; ΔG).
- They don't change spontaneity or equilibrium.
Effect of Enzymes on Reaction Rates
- Enzymes affect reaction kinetics, not thermodynamics.
- Enzymes speed up reactions without being consumed or altered permanently.
- Enzymes may temporarily form transient bonds during catalysis but these bonds must break by the end of the reaction so the enzyme can catalyze additional reactions.
- Enzymes catalyze both forward and reverse reactions, decreasing Ea for both.
Energetic Coupling
- Cells use enzymes to drive endergonic (nonspontaneous) reactions by coupling them with exergonic (spontaneous) reactions.
- In peptide bond formation, enzymes couple it with the hydrolysis of nucleoside triphosphates (NTPs) (often GTP).
Reversible vs. Irreversible Reactions
- Reversible reactions have a ΔG near 0 kJ/mol.
- Irreversible reactions have a large, negative ΔG.
- Small changes in reactant or product concentrations can alter the direction of a reversible reaction, but a spontaneous and irreversible reaction is unlikely to change direction.
- Enzymes catalyze both reversible and irreversible reactions.
Enzyme Behavior
- Enzyme activity relies on interactions between the active site and substrate.
- Enzymes are not consumed by reactions.
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