Question

Coordination compounds have great importance in biological systems. In this context, which of the following statements is incorrect? (a) chlorophylls are green pigments in plants and contain calcium (b) haemoglobin is the red pigment of blood and contains iron (c) cyanocobalamin is vitamin \(\mathrm{B}_{12}\) and contains cobalt (d) carboxypeptidase-A is an enzyme and contains zinc

Short answer

Option (a) is incorrect; chlorophyll contains magnesium, not calcium.

Step-by-step solution

Understand the Components of Coordination Compounds

Coordination compounds are a class of complex compounds consisting of a central atom or ion, usually metallic, and a surrounding array of bound molecules or ions, called ligands. These are fundamentals in biological systems, often found in vitamins, pigments, enzymes, and other biomolecules.

Examine the Role of Metals in Each Option

We will examine each statement for the presence and role of a metal ion: (a) Chlorophylls: Known as the green pigments in plants, chlorophylls typically contain a central magnesium ion (\( \text{Mg} \)), not calcium.(b) Haemoglobin: This blood pigment contains iron (\( \text{Fe} \)) as a central component that facilitates oxygen transport.(c) Cyanocobalamin: Known as vitamin \( \text{B}_{12} \), it contains cobalt (\( \text{Co} \)) as part of its structure.(d) Carboxypeptidase-A: This enzyme contains zinc (\( \text{Zn} \)) which plays a crucial role in its enzyme activity.

Identify the Incorrect Statement

Compare each option against known biological knowledge: - Option (a) is incorrect as chlorophyll contains magnesium, not calcium. - Options (b), (c), and (d) are correct, as they all describe the correct metal components in their respective biological roles.

Key concepts

Biological Systems

Biological systems are incredibly intricate networks of interactions that sustain life. They encompass all living organisms and their complex operations. One fundamental element within these systems is coordination compounds. These are molecules consisting of a central metal ion surrounded by ligands, which are atoms or molecules that donate electrons to the metal ion.

In the realm of biology, coordination compounds are crucial. They can influence processes like oxygen transport, photosynthesis, and even the structure of biomolecules. The role of coordination compounds varies greatly, from forming essential enzymes to acting in processes that convert light into chemical energy.

Ligands

Ligands are molecules or ions that attach to a central metal ion in coordination compounds, forming a complex structure. These ligands are vital because their interactions with metal ions can modulate the biological activities of the resulting compounds.

The nature of ligands can significantly affect the properties of a coordination compound, such as its stability and reactivity. For example, in chlorophyll, the ligands help stabilize the magnesium ion in the molecule, enabling it to efficiently capture light for photosynthesis. In contrast, hemoglobin has iron at its center, but the type of ligands binding this iron is crucial for its ability to transport oxygen through the bloodstream.

Metal Ions

Metal ions play a central role in the functionality of coordination compounds in biological systems. These ions, like iron in hemoglobin or magnesium in chlorophyll, are vital because they often serve as the active centers where chemical reactions occur.

The presence of these metal ions can influence the shape, electronic structure, and ultimately the biochemical activity of the coordination compound. For instance, the iron ion in hemoglobin can reversibly bind to oxygen molecules, a mechanism essential for life. Similarly, in vitamin B12, the presence of a cobalt ion is crucial for its role in DNA synthesis and regulation.

Pigments

Pigments are colored substances produced by living organisms that have a wide range of roles in biological systems. These include light absorption, signal reception, and even protection against radiation damage.

Chlorophyll is a well-known pigment that plays a critical role in photosynthesis, capturing sunlight and converting it into chemical energy. This pigment contains a central magnesium ion, which is vital for its function. Another important biological pigment is hemoglobin, the red pigment in blood, which contains an iron ion and is responsible for transporting oxygen throughout the body.

Enzymes

Enzymes are proteins that act as catalysts in biological reactions, speeding up processes that would otherwise occur too slowly to sustain life. Many enzymes are coordination compounds, where a metal ion at the core enhances their catalytic abilities.

An example of such an enzyme is carboxypeptidase-A, which contains a zinc ion. This ion plays a crucial role in the enzyme's ability to break down proteins by stabilizing the transition state during the reaction. The metal-ligand interactions in these enzymes are what make them uniquely suited to catalyze specific biochemical reactions efficiently.