5.1 Enzymes (3)
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Biology
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1.
Explain why a catalyst does not change the equilibrium position of a reversible reaction. Consider the effect of a catalyst on the forward and reverse reactions.
A catalyst speeds up both the forward and reverse reactions equally. It lowers the activation energy for both processes. Because the activation energy is lowered for both the forward and reverse reactions, the rate at which the forward reaction proceeds is increased by the same proportion as the rate at which the reverse reaction proceeds.
Therefore, while the forward reaction occurs faster and the reverse reaction occurs faster, the rate of the forward reaction relative to the rate of the reverse reaction remains the same. This means that the ratio of products to reactants at equilibrium is not altered. The equilibrium position, which represents the point where the rates of the forward and reverse reactions are equal, is therefore unchanged by the presence of a catalyst. The catalyst simply helps the system reach equilibrium faster.
2.
Draw a simple diagram illustrating the relationship between temperature and the rate of an enzyme-catalyzed reaction. Label the key components involved (kinetic energy, effective collisions, enzyme-substrate fit, denaturation) and indicate the optimal temperature.
Diagram:
[Image missing: Enzyme Temperature Graph] |
Labels:
- X-axis: Temperature
- Y-axis: Rate of Reaction
- Optimal Temperature: Point of highest rate of reaction.
- Denaturation: Point where the rate of reaction drops sharply.
- Kinetic Energy: Represented by the movement of molecules. Higher temperature = higher kinetic energy.
- Effective Collisions: The number of collisions between enzyme and substrate that lead to a reaction. Increased temperature increases effective collisions up to a point.
- Enzyme-Substrate Fit: The degree to which the active site of the enzyme complements the shape of the substrate. Denaturation reduces fit.
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Explanation: The diagram shows a typical bell-shaped curve. As temperature increases from low to optimal, the rate of reaction increases due to increased kinetic energy and more effective collisions. Beyond the optimal temperature, the rate of reaction decreases rapidly due to denaturation of the enzyme, which disrupts the enzyme-substrate fit and reduces the number of effective collisions. The optimal temperature is the point at which the enzyme is most active.
3.
A student states: "Enzymes are important because they allow reactions to happen faster, which means organisms can grow and reproduce more quickly." Evaluate this statement. Consider whether it is a complete explanation and suggest any further points that should be included.
The student's statement is partially correct but incomplete. It correctly identifies that enzymes speed up reactions, which is essential for growth and reproduction. However, it doesn't fully explain why faster reaction rates are so important.
Evaluation:
- Metabolic Rate: Faster reaction rates translate to a higher metabolic rate. This means organisms can process more energy and nutrients in a given time.
- Efficiency: Faster reactions allow organisms to efficiently utilize resources, maximizing energy gain from food or sunlight.
- Regulation: Enzyme activity is tightly regulated, allowing organisms to respond quickly to changing environmental conditions. This regulation is crucial for maintaining homeostasis.
- Complexity of Life: The speed at which biochemical reactions occur is fundamental to the complexity of life. Without enzymes, many complex metabolic pathways would be impossible.
Further Points to Include: The statement could be improved by mentioning the role of enzymes in maintaining homeostasis and the regulation of metabolic pathways. It's not just about speed; it's about the ability to control and coordinate life processes.