Problem 27 - Objective Biology for NEET

Question

Which of the following is true about iron? (a) It is a constituent of ferredoxin and cytochrome. (b) It activates catalase enzyme. (c) It is essential for the formation of chlorophyll. (d) All the above

Step-by-Step Solution

Answer

The correct answer is (d) All the above because each of the provided statements is correct about the role of iron in biological structures and processes.

Step 1: Understanding the Statements

Firstly, let's break down these statements. Ferredoxin and cytochrome are both proteins that participate in electron transfer in cells, and iron is indeed part of their structures. Catalase is an enzyme that breaks down hydrogen peroxide into water and oxygen, and iron is a key part of its structure, thus activating it. Chlorophyll is the green pigment found in plants that helps absorb light for photosynthesis, and iron aids in its formation. So we can see all statements are describing different roles of iron in biological structures and processes.

Step 2: Evaluation of the statements

From the previous pattern recognitions, it is clear that iron plays significant roles across different biological structures and processes. In fact, every single statement about iron's role in ferredoxin, cytochrome, the catalase enzyme, and chlorophyll formation is essentially based on accurate biological features. We can conclude all these statements are indeed true.

Step 3: Final Judgment

Since all three individual statements are correct according to the role which iron plays, it means that the correct answer to the question, Which of the following is true about iron?, is (d) All the above.

Key Concepts

Ferredoxin

Ferredoxin is a small iron-sulfur protein that plays a crucial role in various biological processes. It is widely known for its function in photosynthesis, where it facilitates electron transfer. This protein is integral to the light reactions of photosynthesis, acting as an electron shuttle between photosystem I and various enzymes. Without ferredoxin, plants would struggle to convert sunlight into chemical energy.

Ferredoxin's structure involves iron atoms coordinated with sulfur, forming clusters that are essential for its electron transfer capabilities. This makes iron a vital component of ferredoxin, directly influencing its functionality. In addition to photosynthesis, ferredoxin also has important roles in nitrogen fixation in some bacteria, showcasing its versatility.

Cytochrome

Cytochromes are a group of proteins that contain heme groups and are predominant in electron transport chains. Their primary function is to facilitate electron transfer processes in cells. Electrons are passed from one cytochrome to another along a chain, allowing the cell to harvest energy efficiently.

Each cytochrome contains an iron atom within its heme group. The iron alternates between different oxidation states as it shuttles electrons. This essential role makes iron a central player in the function of these proteins. Cytochromes are found in both mitochondria and chloroplasts, playing critical roles in cellular respiration and photosynthesis alike. Their presence in these organelles highlights their importance in energy conversion processes.

Catalase Enzyme

Catalase is an important enzyme that helps protect cells from oxidative damage. It does this by breaking down hydrogen peroxide, a potentially harmful by-product of cellular metabolism, into water and oxygen. This reaction is crucial for maintaining cellular health, as excessive hydrogen peroxide can lead to oxidative stress and damage.

The structure of catalase includes iron, which is essential for its activity. Iron acts as a cofactor, enabling the enzyme to perform the reaction efficiently. Without iron, catalase would be unable to catalyze the breakdown of hydrogen peroxide, leading to potential accumulation of this detrimental compound in cells.

Chlorophyll Formation

Chlorophyll is the green pigment that allows plants to capture light energy and perform photosynthesis. It is predominantly found in chloroplasts, where it absorbs sunlight and converts it into chemical energy. However, the formation of chlorophyll is a complex process that requires iron.

Iron is a critical element in the synthesis of chlorophyll. It acts as a catalyst in various enzymatic reactions involved in chlorophyll biosynthesis. Plants without sufficient iron often exhibit chlorosis, a condition where leaves become yellow due to inadequate chlorophyll production. This demonstrates the indispensable role of iron in plant health and growth, emphasizing its necessity in agricultural and ecological contexts.