Which of the following statements correctly describe(s) the role or roles of heat in biological reactions?

• A. Heat from the environment is necessary for substrates to get over the activation energy barrier.
• B. The kinetic energy of the substrates is increased as the amount of heat in the system is increased.
• C. Increasing the amount of heat in a system will always increase the rate of enzyme-catalyzed reactions.
• D. The second and third choices are correct.
• E. The first and second choices are correct.

Answer: (E)

Verified step by step guidance

1. Understand the concept of activation energy: Activation energy is the minimum amount of energy required for a chemical reaction to occur. In biological systems, this energy is often provided by heat from the environment, which helps substrates overcome this barrier.
2. Analyze the first statement: 'Heat from the environment is necessary for substrates to get over the activation energy barrier.' This statement is correct because heat provides the energy needed for substrates to reach the transition state and proceed with the reaction.
3. Examine the second statement: 'The kinetic energy of the substrates is increased as the amount of heat in the system is increased.' This is also correct because increasing heat raises the kinetic energy of molecules, making them move faster and collide more frequently, which can lead to more successful reactions.
4. Evaluate the third statement: 'Increasing the amount of heat in a system will always increase the rate of enzyme-catalyzed reactions.' This statement is incorrect because while heat can increase reaction rates, excessive heat can denature enzymes, reducing their activity or stopping the reaction.
5. Conclude with the correct answer: The first and second choices are correct because they accurately describe the role of heat in biological reactions, while the third choice is incorrect due to the potential negative effects of excessive heat on enzyme activity.