Question

When lactase hydrolyzes its substrate, lactose, which of the following occurs? A. Lactase retains its structure after the reaction. B. Lactose retains its structure after the reaction. C. Lactase increases the activation energy of the reaction. D. Lactose decreases the activation energy of the reaction.

Short answer

A. Lactase retains its structure after the reaction.

Step-by-step solution

Understand Enzyme Behavior

Lactase is an enzyme that catalyzes the hydrolysis of lactose. Enzymes are proteins that speed up chemical reactions without being consumed or permanently changed in the process. Therefore, they retain their structure after the reaction.

Evaluate Lactose Structure

Lactose, being the substrate, undergoes a chemical change. It is broken down into glucose and galactose after the reaction, so it does not retain its structure.

Activation Energy Insights

Enzymes work by lowering the activation energy of a reaction, not increasing it. This allows the reaction to proceed more quickly and efficiently.

Analyzing Incorrect Options

D is incorrect because it suggests that the substrate, lactose, affects the activation energy. However, it is the lactase (enzyme) that affects activation energy, not the substrate.

Selecting the Correct Answer

Based on these analyses, A is correct: Lactase retains its structure after the reaction.

Key concepts

enzyme function

Enzymes are special proteins that act as catalysts in biological reactions. They help speed up chemical reactions without being consumed or permanently changed in the process. In this exercise, lactase is the enzyme that hydrolyzes lactose. Think of enzymes like machines in a factory; they keep working on the materials passing through them without wearing out.
Lactase helps break down lactose, a sugar found in milk, into simpler sugars — glucose and galactose.
Because of this ability, enzymes play vital roles in various bodily functions, including digestion, metabolism, and even energy production. Enzymes are highly specific — each one usually only works on a particular substrate (the substance on which an enzyme acts).

activation energy

Activation energy is the minimum amount of energy needed for a chemical reaction to occur. Think of it like pushing a rock up a hill; you need to exert some initial force to get it started. In biological reactions, enzymes like lactase lower the amount of activation energy required.
This makes it easier for the reaction to proceed quickly and efficiently.

Instead of the cell needing a huge amount of energy to break down lactose, lactase makes the process much more manageable. For example, in the absence of an enzyme, a reaction might need a very high temperature to occur. But with an enzyme, the same reaction can take place at body temperature.

substrate hydrolysis

Substrate hydrolysis refers to the process where a substance (substrate) is broken down by adding water. In this case, lactase hydrolyzes lactose. This means it helps water molecules split lactose into glucose and galactose.
The term 'hydrolysis' comes from two words: 'hydro' (water) and 'lysis' (to break).

Just imagine pouring water on something to break it apart, much like how lactase uses water to break down lactose.
After hydrolysis, the original substrate (lactose) does not retain its structure. Instead, it changes into different products, which are easier for the body to absorb and use.

enzyme-substrate interaction

Enzyme-substrate interaction is a crucial step in enzymatic reactions. The enzyme (like lactase) and the substrate (like lactose) interact in a very specific way. They fit together like a lock and key.
When lactase binds to lactose, it forms an enzyme-substrate complex. This interaction helps to lower the activation energy required for the reaction.

After the reaction, the enzyme releases the products and returns to its original state, ready to catalyze another reaction. The key point is that while the substrate undergoes a chemical change, the enzyme itself remains unchanged and can be reused repeatedly.
This incredible efficiency is what makes enzymes so important in sustaining life processes.