Problem 114 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statements is correct? (a) the metal ion present in vitamin \(\mathrm{B}_{12}\) is \(\mathrm{Zn}^{2+}\) (b) in photosynthesis \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\) are converted into carbohydrates in presence of sunlight (c) in haemoglobin the oxidation state of \(\mathrm{Fe}\) is \(+6\). (d) methyl salicylate is known as aspirin

Step-by-Step Solution

Answer

Statement (b) is correct.

Step 1: Analyze Statement (a)

Statement (a) claims that the metal ion present in vitamin B12 is \( \mathrm{Zn}^{2+} \). However, vitamin B12 contains a cobalt ion \( \mathrm{Co}^{3+} \) within its structure. Therefore, statement (a) is incorrect.

Step 2: Evaluate Statement (b)

Statement (b) states that in photosynthesis, \( \mathrm{CO}_{2} \) and \( \mathrm{H}_{2} \mathrm{O} \) are converted into carbohydrates in the presence of sunlight. This is the fundamental process of photosynthesis where plants convert carbon dioxide and water into glucose and oxygen, using sunlight. This statement is correct.

Step 3: Inspect Statement (c)

Statement (c) mentions that the oxidation state of \( \mathrm{Fe} \) in hemoglobin is \(+6\). Normally, iron in hemoglobin exists in the \(+2\) oxidation state as \( \mathrm{Fe}^{2+} \) to bind oxygen. Hence, this statement is incorrect.

Step 4: Examine Statement (d)

Statement (d) claims that methyl salicylate is known as aspirin. In reality, aspirin is acetylsalicylic acid, while methyl salicylate is a different compound, commonly known as oil of wintergreen. Therefore, statement (d) is incorrect.

Key Concepts

Vitamin B12

Vitamin B12, also known as cobalamin, is a crucial vitamin needed for nerve tissue health, brain function, and red blood cell production. Unlike many vitamins, Vitamin B12 contains a metal ion at its core, making it a unique molecule. The metal ion present in this vitamin is cobalt, specifically in the form of a cobalt ion (\( \mathrm{Co}^{3+} \)).
This cobalt ion is central to the structure of Vitamin B12 and plays a vital role in its function. The cobalt is bonded to a corrin ring, which is similar to the more well-known heme ring found in hemoglobin, but with a different ring structure. Vitamin B12 is also necessary for DNA synthesis and regulation, which highlights its importance in cell formation.

• It is obtained through dietary sources like meat, eggs, and dairy products.
• Deficiency in Vitamin B12 can lead to symptoms such as fatigue, weakness, and neurological impairments.

Thus, ensuring an adequate intake of Vitamin B12 in your diet is essential for maintaining good health.

Photosynthesis

Photosynthesis is one of the most important biological processes on Earth, allowing plants, algae, and some bacteria to convert light energy into chemical energy. This process utilizes carbon dioxide (\( \mathrm{CO}_{2} \)) and water (\( \mathrm{H}_{2} \mathrm{O} \)), transforming them into glucose and oxygen as products.
Sunlight is the primary energy source that drives photosynthesis. It is absorbed by chlorophyll, the green pigment in plant leaves. Here is an overview of the photosynthesis process:

• Light-dependent reactions: The energy from sunlight splits water molecules, releasing oxygen and generating energy-rich molecules, ATP and NADPH.
• Light-independent reactions (Calvin Cycle): ATP and NADPH convert carbon dioxide into glucose, which serves as an energy source for plants and, indirectly, for animals that consume these plants.

This natural process not only provides oxygen for us to breathe but also forms the base of the food chain, making it a vital process for life on Earth.

Hemoglobin

Hemoglobin is a protein found in red blood cells responsible for carrying oxygen from the lungs to the rest of the body and returning carbon dioxide from the tissues back to the lungs. The key component of hemoglobin that allows it to perform this function is an iron ion.
The iron in hemoglobin is in the \( +2 \) oxidation state, known as ferrous iron (\( \mathrm{Fe}^{2+} \)), which is capable of binding oxygen molecules. This binding is reversible, allowing hemoglobin to pick up and release oxygen where needed. Here are some key points about hemoglobin:

• Hemoglobin is made up of four subunits, each containing one iron atom.
• The iron ion is embedded in a heme group, which is a small, ring-like structure.
• This iron-centered heme is what allows hemoglobin to bind to oxygen efficiently.

Interruption in the function or structure of hemoglobin can lead to various health issues like anemia, making its role in the body critical.

Aspirin Chemistry

Aspirin, scientifically known as acetylsalicylic acid, is a widely used medication known for its pain-relieving, anti-inflammatory, and antipyretic properties. It works by inhibiting certain enzymes in the body that lead to inflammation and pain.
Despite popular misconceptions, aspirin is not the same as methyl salicylate. Methyl salicylate, often referred to as "oil of wintergreen," is chemically distinct, though it shares some similar properties. Here’s a closer look at aspirin chemistry:

• Aspirin works by blocking cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis, which diminishes pain and swelling.
• It was originally derived from willow bark, which contains salicin, a compound related to salicylic acid.
• Aspirin is also used for its anticoagulant properties, preventing blood clots and reducing the risk of heart attacks and strokes.

Despite its benefits, overuse of aspirin can lead to side effects, including gastrointestinal issues, demonstrating the importance of using medications responsibly.