Problem 108 - Objective Biology for NEET

Question

Assertion: Iron takes part in the electron transport system of mitochondria. Reason: Iron has no role in chlorophyll synthesis.

Step-by-Step Solution

Answer

The assertion is correct and the reason is unrelated to the assertion. The reason does not correctly justify the assertion.

Step 1: Role of iron in the Electron Transport Chain (ETC)

Identify and understand the role of iron in the ETC. Iron is a component of cytochromes which are proteins involved in the Electron Transport Chain. In the ETC process, electrons are transferred from electron donors to electron acceptors through redox reactions. This process helps in ATP (Adenosine Triphosphate) synthesis. Thus, iron does play a part in the ETC of mitochondria.

Step 2: Role of iron in chlorophyll synthesis

Understand the role of iron in chlorophyll synthesis. Chlorophyll is the green pigment present in plants which helps in photosynthesis. Iron is not directly involved in the synthesis of chlorophyll. However, iron deficiency can cause chlorosis, a condition characterized by insufficient chlorophyll. Still, it can be concluded that iron does not exactly have a role in chlorophyll synthesis as iron is not a component of the chlorophyll molecule.

Step 3: Compare Assertion and Reason

Iron's role in the ETC of mitochondria (Assertion) is correct. However, its role in chlorophyll synthesis (Reason) is irrelevant to the assertion as these two are different biological processes. Thus, the reason does not provide a correct explanation for the assertion.

Key Concepts

Electron Transport Chain

The Electron Transport Chain (ETC) is a crucial process in cells that helps generate energy. This chain is part of cellular respiration and takes place in the mitochondria. The primary goal of the ETC is to produce ATP, the energy currency of cells.

In the ETC, electrons are passed along a series of complexes and proteins. These electrons come from molecules like NADH and FADH2, which are generated in earlier steps of respiration. The transfer of electrons through the chain allows for the pumping of protons across the mitochondrial membrane. This creates a gradient, and when protons flow back across the membrane, ATP is synthesized.

Iron plays a vital part in the ETC. It is found in proteins called cytochromes, which are involved in transporting electrons. These proteins contain heme groups that have iron ions. Iron's ability to change its oxidation state makes it perfect for moving electrons in the chain, enabling the vital process of ATP production.

Chlorophyll Synthesis

Chlorophyll is the green pigment found in plants necessary for absorbing sunlight during photosynthesis. While iron is not a direct participant in chlorophyll synthesis, its presence is essential for healthy chloroplast function.

Plants suffering from iron deficiency often develop a condition known as chlorosis. This leads to yellowing leaves due to inadequate chlorophyll. Although iron is not part of the chlorophyll molecule itself, it is involved in the biosynthesis of some compounds necessary for chlorophyll production.

Iron's role here highlights an indirect yet crucial support in maintaining overall plant health and optimizing the plant's ability to undergo photosynthesis effectively. Without sufficient iron, the production of chlorophyll can be hampered, which affects the plant’s growth and energy acquisition.

Cytochromes

Cytochromes are specialized proteins that play a fundamental role within the Electron Transport Chain. They are integral to both cellular respiration in mitochondria and photosynthesis in chloroplasts.

These proteins contain heme groups that consist of a central iron atom. The iron atom is crucial because it alternates between different oxidation states, facilitating the transfer of electrons. This property makes cytochromes efficient mediators in electron transport.

Through electron transfer, cytochromes help drive the synthesis of ATP in cellular respiration. In photosynthesis, they assist in transferring energy captured from light. The dual role of cytochromes in these essential pathways underscores their versatility and importance in both plant and animal cells. Cytochromes exemplify how iron serves as a critical component of life-sustaining biochemical processes.