Problem 61 - A Complete Resource Book in Chemistry for JEE Main

Question

The pair in which both species have iron is (a) nitrogenase, cytochromes (b) carboxypeptidase, haemoglobin (c) haemocyanin, nitrogenase (d) haemoglobin cytochromes

Step-by-Step Solution

Answer

The correct pair is (d) haemoglobin, cytochromes.

Step 1: Understanding the Question

The question asks which pair of species both contain iron. We are given four options, each containing two species, and need to identify the pair where both species have iron.

Step 2: Analyzing the Options

Review each option to understand which species contain iron. (a) Nitrogenase contains iron as it is an iron-sulfur protein, cytochromes contain iron as part of the heme group. (b) Carboxypeptidase contains zinc, haemoglobin contains iron in its heme group. (c) Haemocyanin uses copper, nitrogenase contains iron. (d) Haemoglobin contains iron in its heme group, cytochromes also contain iron in their heme group.

Step 3: Identifying the Correct Pair

Both nitrogenase and cytochromes are iron-containing, making option (a) a correct pair. Haemoglobin and cytochromes also both contain iron, making option (d) a correct pair.

Step 4: Selecting the Correct Answer

Since option (d) is a pair where both species have iron (haemoglobin and cytochromes both contain iron), option (d) is the correct answer.

Key Concepts

Nitrogenase

Nitrogenase is an essential enzyme in the world of biology, playing a vital role in the process of nitrogen fixation. This means it helps convert atmospheric nitrogen () into ammonia (). This transformation is crucial for living organisms, as ammonia is a necessary building block for making proteins and other important biomolecules.
A key component of nitrogenase is its iron-sulfur clusters, which are responsible for the enzyme's ability to bind and reduce nitrogen. These clusters consist of iron atoms that work together with sulfur atoms to carry out this important chemical reaction.
Because of this, nitrogenase is an iron-containing biomolecule, vital for the biosphere's nitrogen cycle. It is found in certain bacteria that live in the soil or in symbiotic relationships with plants, like legumes. This relationship enhances soil fertility by naturally providing nitrogen compounds that plants can use.

Cytochromes

Cytochromes are a group of proteins found in many living organisms, and they play a critical role in the electron transport chain, which is part of cellular respiration. This process is what cells use to extract energy from nutrients.
Cytochromes contain a heme group, which is a complex molecule that includes an iron atom at its center. This iron atom can easily switch between different oxidation states, allowing it to effectively transfer electrons between molecules during the electron transport process.
Through these electron transfers, cytochromes contribute to the creation of a proton gradient across the inner mitochondrial membrane. This gradient is then used by the enzyme ATP synthase to produce ATP, the energy currency of the cell. Therefore, cytochromes are crucial for energy production in living cells.

• Part of cellular respiration
• Contain heme group with iron
• Essential for electron transfer

Haemoglobin

Haemoglobin is a fascinating protein found in red blood cells, and it is key to transporting oxygen throughout our bodies. This protein gives blood its red color, thanks to the iron-containing heme group at the center of each haemoglobin molecule.
Haemoglobin functions by binding to oxygen in the lungs, where oxygen concentration is high, and then releasing it in tissues where it's needed most. This process is facilitated by the iron atom in the heme group, which temporarily binds to oxygen molecules.
Besides oxygen transport, haemoglobin also plays a role in transporting carbon dioxide, a waste product, from tissues back to the lungs for exhalation. This dual functionality makes it a critical component for maintaining the health and efficiency of our respiratory system.

• Oxygen transport in blood
• Contains iron in heme group
• Releases and binds oxygen efficiently