Question

In the enzyme peroxidase anhydrase, the percentage of selenium (Se) by mass is \(0.5 \%\). If atomic mass of Se is \(78.4 \mathrm{U}\), then minimum molecular mass of peroxidase anhydrase enzyme is: (a) \(1.568 \times 10^{3} \mathrm{U}\) (b) \(1.568 \times 10^{4} \mathrm{U}\) (c) \(1.568 \mathrm{U}\) (d) \(2.136 \times 10^{4} \mathrm{U}\)

Short answer

The minimum molecular mass of peroxidase anhydrase is \(1.568 \times 10^{4} \mathrm{U}\).

Step-by-step solution

Understanding the Problem

We need to calculate the minimum molecular mass of an enzyme in which selenium (Se) constitutes 0.5% by mass. We are given that the atomic mass of selenium is 78.4 U.

Set Up the Percentage Equation

The mass percentage of selenium in the enzyme is given by the formula: \[ \text{Mass Percentage} = \frac{\text{Mass of Se}}{\text{Molecular Mass of Enzyme}} \times 100 \]Here, the mass percentage is 0.5%, and the atomic mass of selenium (the mass of Se) is 78.4 U.

Write the Equation for Molecular Mass

We need to find the molecular mass (M) of the enzyme. Using the percentage formula:\[ 0.5 = \frac{78.4}{M} \times 100 \]We will solve this equation to find M.

Solve for Molecular Mass M

Rearrange the equation to solve for M:\[ M = \frac{78.4 \times 100}{0.5} \]Calculate to find:\[ M = 15680 \]

Conclusion and Answer Verification

The minimum molecular mass of the enzyme is calculated to be 15680 U. Comparing with the given options, it matches with option (b).

Key concepts

Percentage by Mass

The term percentage by mass refers to the proportion of a specific component in a substance, expressed as a percentage of the total mass. This is a valuable concept in chemistry, particularly when analyzing the composition of compounds and mixtures.
To calculate the percentage by mass, you can use this formula:

• Take the mass of the substance you are interested in.
• Divide it by the total mass of the mixture.
• Multiply the result by 100 to get the percentage.

For example, if selenium constitutes 0.5% of the enzyme by mass, this means that in every 100 grams of the enzyme, 0.5 grams are selenium.
This interpretation helps understand how elements contribute to the composition of complex molecules like enzymes. Knowing the mass percentage allows chemists to deduce necessary conditions in reactions or compare the abundance of elements within substances.

Enzyme Composition

Enzymes are remarkable biological molecules that speed up chemical reactions in living organisms. They are usually proteins and are composed of chains of amino acids. However, some enzymes, like peroxidase anhydrase, have metallic elements such as selenium in their structure.
Selenium is vital for the functioning of certain enzymes, often called selenoenzymes. In our exercise, selenium makes up 0.5% of the enzyme peroxidase anhydrase by mass.
Understanding enzyme composition is crucial because:

• It helps determine the enzyme's structure and how it functions.
• The presence of elements like selenium is important for the active sites of enzymes, which are critical for catalytic activity.
• It assists in research and development of enzyme-based therapies and industrial applications.

Enzymes' efficiency and specificity are deeply tied to their composition, which makes understanding elements contributing to their makeup essential for biochemistry.

Atomic Mass

Atomic mass is a fundamental concept in chemistry that refers to the mass of an atom, usually expressed in atomic mass units (u) where one unit is defined as one twelfth of the mass of a carbon-12 atom. This mass is calculated considering the atom's protons and neutrons, as electrons contribute negligible mass.
In the context of our task, knowing the atomic mass of selenium (78.4 u) is the starting point for calculating the enzyme's minimum molecular mass. This is because we know selenium forms a proportionate part of the enzyme and it is essential when solving for other components of the enzyme's structure.
When using atomic mass to understand enzyme structures or any molecular arrangements:

• It provides information about the proportions of different elements within a molecule.
• A precise measurement aids in predicting how elements will react and interact in chemical processes.
• It aids in calculating the molecular formulas of compounds, predicting physical properties, and stoichiometry in reactions.

By incorporating the known atomic masses, chemists can develop a comprehensive understanding of how substances are structured and forecast their chemical behavior effectively.