Question

Enzymes increase the rate of a reaction by: (A) decreasing the activation energy. (B) decreasing the overall free energy change of the reaction. (C) increasing the activation energy. (D) increasing the overall free energy change of the reaction.

Short answer

A

Step-by-step solution

Understand what enzymes do

Enzymes are biological catalysts that speed up chemical reactions in cells. They do this by lowering the activation energy needed for the reaction to proceed.

Define Activation Energy

Activation energy is the minimum amount of energy required to start a chemical reaction. By lowering this barrier, enzymes enable reactions to occur more quickly and efficiently.

Evaluate the given options

Look at each option: (A) decreasing the activation energy. (B) decreasing the overall free energy change of the reaction. (C) increasing the activation energy. (D) increasing the overall free energy change of the reaction.

Eliminate incorrect choices

Exclude options that do not match the role of enzymes:- Option B and D: Enzymes do not change the overall free energy change of the reaction.- Option C: Enzymes decrease, not increase, the activation energy.

Choose the correct option

The correct choice is option (A): Enzymes increase the rate of a reaction by decreasing the activation energy.

Key concepts

activation energy

Activation energy is a crucial concept in understanding how chemical reactions occur. It refers to the minimum amount of energy required to start a chemical reaction. Imagine you are trying to push a heavy boulder up a hill. You need a certain amount of energy to get it up to the top. Once it’s on the other side, the boulder rolls down easily. Activation energy works similarly. It is the 'hill' that reactants must overcome to transform into products. Enzymes help by reducing this ‘hill’ or action energy, making it easier for the reaction to occur. By lowering the activation energy, enzymes enable reactions to happen faster and more efficiently, which is crucial for the functioning of biological systems.

biological catalysts

Enzymes are biological catalysts. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. In biological systems, enzymes perform this role. They are typically proteins that have a unique three-dimensional structure. This structure allows them to bind to specific molecules called substrates. Once bound, enzymes work by lowering the activation energy required for the reaction. This ability to lower activation energy comes from the way enzymes stabilize the transition state of the reaction. Transition states are high-energy states that occur during the transformation from reactants to products. By stabilizing these states, enzymes reduce the energy barrier, speeding up the reaction. As a result, reactions that might take place slowly or not at all under normal conditions can occur rapidly.

reaction rate

The reaction rate is a measure of how quickly a chemical reaction occurs. In the context of enzymes, the reaction rate refers to the speed at which the enzyme converts substrates into products. Several factors influence the reaction rate: temperature, pH, and substrate concentration are among them. Enzymes increase reaction rates by up to a million times compared to reactions without catalysts. This dramatic increase is due to their ability to lower activation energy. By facilitating faster reaction rates, enzymes allow cells to carry out necessary biochemical processes efficiently.
For example, the enzyme catalase speeds up the breakdown of hydrogen peroxide into water and oxygen. Without catalase, this reaction would be too slow to protect cells from harmful hydrogen peroxide accumulation. Thus, enzymes play an essential role in maintaining life by ensuring that biochemical reactions occur at appropriate rates.