Question

Which of the following biomolecules contain nontransition metal ion? (a) vitamin \(\mathrm{B}_{12}\) (b) chlorophyll (c) haemoglobin (d) insulin

Short answer

Chlorophyll contains a nontransition metal ion (magnesium).

Step-by-step solution

Understanding the Question

We need to identify which of the given biomolecules contains a nontransition metal ion. This involves checking each option to see which metal ion is present.

Analyzing Option (a): Vitamin B12

Vitamin B12 contains a cobalt ion at its core. Since cobalt is a transition metal, it does not fit the criteria of containing a nontransition metal ion.

Analyzing Option (b): Chlorophyll

Chlorophyll contains a magnesium ion. Magnesium is an alkaline earth metal and is not a transition metal.

Analyzing Option (c): Haemoglobin

Haemoglobin contains iron in the form of heme. Iron is a transition metal, so this option does not meet the criteria for a nontransition metal ion.

Analyzing Option (d): Insulin

Insulin is a protein hormone that primarily consists of amino acids and does not contain a metal ion as a key component.

Conclusion

Based on the analysis, chlorophyll is the only biomolecule among the options that contains a nontransition metal ion (magnesium).

Key concepts

Transition Metals

Transition metals are elements found in the center of the periodic table, specifically in groups 3 through 12. These metals are characterized by their ability to form multiple oxidation states, which means they can lose different numbers of electrons. This gives them a unique ability to participate in various chemical reactions. Transition metals are also known for their ability to form colorful compounds due to electron transitions within their d orbitals.
Common examples of transition metals include iron (Fe), cobalt (Co), and nickel (Ni).

• They often serve as catalysts in chemical reactions.
• Have high melting and boiling points.
• Exhibit magnetic properties.

In the context of biomolecules, transition metals play critical roles in the structure and function of molecules such as vitamin B12 and haemoglobin.

Vitamin B12

Vitamin B12, also known as cobalamin, is an essential vitamin involved in multiple bodily functions. It's crucial for DNA synthesis, red blood cell formation, and neurological function. What makes vitamin B12 unique among vitamins is its metal ion center containing cobalt, a transition metal.
The cobalt ion in vitamin B12 can exist in different oxidation states, which is significant for its biological functions. This transition metal allows vitamin B12 to participate in enzymatic processes crucial for energy production and synthesis of critical biomolecules.

• Sources include meat, eggs, and dairy products.
• Deficiency can lead to anemia and neurological issues.
• Often found in supplements for vegans as plant-based diets may lack it.

Understanding the transition metal nature of vitamin B12 can help students appreciate its biochemical versatility.

Chlorophyll

Chlorophyll is the green pigment found in plants and algae that enables them to photosynthesize. It is responsible for capturing light energy and converting it into chemical energy, which supports plant growth and food production.
Magnesium, an alkaline earth metal, is at the heart of the chlorophyll molecule. Unlike transition metals, magnesium forms more stable compounds with fewer variations in oxidation states, making it ideal for the stable interactions needed in photosynthesis.
The structure of chlorophyll includes a porphyrin ring similar to haemoglobin, but instead of iron, it contains magnesium. Some key points about chlorophyll are:

• Essential for photosynthesis—turning light energy into chemical energy.
• Gives plants their green color.
• Exists in several forms, most commonly chlorophyll a and b.

This makes chlorophyll distinct because it contains a nontransition metal at its core, unlike the other biomolecules within the exercise.

Haemoglobin

Haemoglobin is a protein found in red blood cells, vital for transporting oxygen from the lungs to the body's tissues. It consists of four subunits, each with an iron-containing heme group at its center. Iron, a transition metal, plays a critical role in haemoglobin's ability to bind oxygen.
The iron within the heme group can oscillate between oxidation states, allowing binding and release of oxygen as it travels through the bloodstream. This ability to bind and release oxygen efficiently showcases the importance of transition metals in biological systems.

• Essential for oxygen transport in vertebrates.
• Each haemoglobin molecule can bind up to four oxygen molecules.
• Abnormal haemoglobin can lead to disorders like sickle cell anemia.

Understanding haemoglobin's structure and function highlights the intricate role of transition metals in biological mechanisms.

Insulin

Insulin is a hormone crucial for regulating blood glucose levels. Produced by the beta cells in the pancreas, it allows cells to absorb glucose from the bloodstream for energy or storage. Unlike the other biomolecules discussed, insulin does not contain a metal ion.
Insulin is a protein made up of amino acids, forming two chains (A and B) connected by disulfide bonds. Its function is purely based on its protein structure, without the need for metal ions.
Key points about insulin include:

• Essential for glucose metabolism and energy utilization.
• Deficiency or insulin resistance can lead to diabetes mellitus.
• Can be purified and synthesized for therapeutic use.

Insulin's role exemplifies the diversity of biomolecules in biological systems, functioning without the involvement of metal ions.