Problem 35 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is correct about enzymes? (a) it reduces the activation energy (b) it increases the activation energy (c) it changes the equilibrium constant (d) none of these

Step-by-Step Solution

Answer

(a) it reduces the activation energy.

Step 1: Understanding the Role of Enzymes

Enzymes are biological catalysts that increase the rate of a chemical reaction without being consumed in the process. They achieve this by lowering the activation energy required for the reaction to proceed.

Step 2: Activation Energy Reduction

The activation energy is the minimum amount of energy needed for a chemical reaction to occur. Enzymes work by providing an alternative reaction pathway with a lower activation energy, thereby speeding up the reaction.

Step 3: Analyzing the Answer Choices

Given the choices, (a) states that enzymes reduce the activation energy, which aligns with their functional role. Choice (b) incorrectly suggests that enzymes increase activation energy, which would slow down reactions instead of speeding them up. Choice (c) suggests that enzymes change the equilibrium constant, but they do not affect the position of the equilibrium, only the rate at which equilibrium is achieved. Choice (d) states 'none of these,' which can be disregarded because option (a) is correct.

Step 4: Selecting the Correct Choice

Based on the analysis of each option and understanding how enzymes function, choice (a) is correct. Enzymes reduce the activation energy of chemical reactions.

Key Concepts

Activation Energy

Activation energy is a crucial concept in understanding how chemical reactions occur. It refers to the minimum amount of energy that reactant molecules need to possess for a reaction to take place. Consider it as an energy barrier that must be overcome for a reaction to progress from reactants to products. Without sufficient activation energy, the reactants will remain in their current state, unable to transform into products. Enzymes play a significant role in influencing activation energy.

• They offer an alternative pathway with a lower activation energy.
• This allows reactions to occur more readily and at a much faster rate.

Lowering activation energy does not alter the starting and ending energy levels of the reactants and products. Instead, it makes the path towards the products energetically more favorable, enabling reactions that would otherwise be too slow to sustain life processes.

Chemical Reactions

Chemical reactions involve the transformation of substances through the breaking and forming of chemical bonds. These reactions are central to biological systems, as they enable the conversion of nutrients into energy, the synthesis of new molecules, and the regulation of cellular activities. Reactions can vary significantly in speed, depending on factors like temperature and pH. Enzymes exert a powerful influence on these reactions:

• They enhance the reaction rate without being consumed.
• They provide specificity, ensuring that the correct reaction takes place.

By lowering the activation energy, enzymes ensure that vital biochemical reactions occur quickly enough to support life. This catalytic property is vital for maintaining the metabolic processes within organisms at an efficiency level that is necessary for survival.

Biological Catalysts

Enzymes are a type of biological catalyst, crucial for the acceleration of chemical reactions within living organisms. A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. Consider enzymes as precise tools that facilitate specific biological processes:

• They speed up reactions by reducing activation energy.
• They allow cells to carry out complex processes within a feasible timescale.
• Each enzyme is specific to its substrate due to its unique active site.

The specificity of enzymes ensures that they facilitate only the desired reaction, which minimizes the risk of undesired side reactions. This specificity is a hallmark of enzyme action, allowing them to regulate the pathways essential for life.

Equilibrium Constant

The equilibrium constant (\( K_{eq} \)) provides a measure of the position of equilibrium in a reversible chemical reaction. It is represented by the ratio of the concentrations of products to reactants at equilibrium. Enzymes, despite their role in enhancing reaction rates, do not alter the equilibrium constant of a reaction:

• The equilibrium position is dictated by the energy levels of the reactants and products.
• While enzymes facilitate the approach to equilibrium faster, they do not change the ratio of concentrations at which equilibrium is achieved.

This means that while enzymes can accelerate the rate at which equilibrium is reached, they do not affect the balance of reactants and products in the final equilibrium state. This distinction is important as it underlines the role of enzymes in reaction kinetics rather than in thermodynamics or equilibrium position.