Problem 33 - Chemistry in 30 days

Question

Co-ordination compounds have great importance in biological systems, in this conick which of the following statements is incorrect? (a) Chlorophyll is a green pigment in plants and contains calcium (b) Haemoglobin is the red pigment of blood and contains iron (c) Cyanocobalamin is \(\mathrm{B}_{12}\) and contains cobalt (d) Carboxypeptidase \(\mathrm{A}\) is an enzyme and contains zinc

Step-by-Step Solution

Answer

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

Step 1: Analyze the Options

First, we need to evaluate each statement provided to determine which one contains incorrect information about coordination compounds in biological systems. Let's review each option one by one:

Step 2: Evaluate Option (a)

Option (a) states that chlorophyll is a green pigment in plants and contains calcium. Actually, chlorophyll contains magnesium at its core, not calcium. Thus, option (a) is likely incorrect.

Step 3: Evaluate Option (b)

Option (b) states that hemoglobin is the red pigment of blood and contains iron. This is true; hemoglobin is responsible for carrying oxygen in the blood and contains iron in its heme groups.

Step 4: Evaluate Option (c)

Option (c) states that cyanocobalamin is vitamin B12 and contains cobalt. This is correct, as vitamin B12, known as cyanocobalamin, contains a cobalt ion.

Step 5: Evaluate Option (d)

Option (d) states that carboxypeptidase A is an enzyme and contains zinc. This statement is accurate; carboxypeptidase A is a metalloenzyme that requires zinc as a cofactor for its enzymatic activity.

Step 6: Conclusion on Incorrect Statement

After evaluating each statement, we find that option (a) is incorrect because chlorophyll contains magnesium, not calcium.

Key Concepts

Chlorophyll

Chlorophyll is the vibrant green pigment essential for photosynthesis in plants. It is responsible for capturing light energy from the sun, which is converted into chemical energy within plant cells. The heart of chlorophyll's structure is a porphyrin ring with a magnesium ion at its core, not calcium as sometimes mistakenly assumed.
- This magnesium ion plays a key role in stabilizing the chlorophyll molecule and is crucial for its function in photosynthesis. - Photosynthesis cannot occur without chlorophyll; it is vital for producing oxygen and organic compounds that are the foundation of life on Earth.
Plants primarily contain chlorophyll "a" and "b" with slightly different roles but working together to absorb light efficiently. The presence of chlorophyll not only gives plants their green color but sustains the life cycle by facilitating the production of glucose from carbon dioxide and water.

Haemoglobin

Haemoglobin is a complex protein found in red blood cells, essential for transporting oxygen from the lungs to all body tissues while bringing carbon dioxide back to the lungs for exhalation. Comprised of four protein subunits, each containing an iron-bound heme group, haemoglobin is red due to the iron within these heme groups.
- The iron ion at the center of the heme plays a pivotal role in oxygen binding. - Each haemoglobin molecule can carry up to four oxygen molecules at once.
Haemoglobin not only functions as an oxygen transporter but also helps maintain the pH balance in blood, acting as a buffer that regulates the acid-base balance during metabolism.

Cyanocobalamin Vitamin B12

Cyanocobalamin, widely recognized as Vitamin B12, is a water-soluble vitamin that plays vital roles in the body, primarily in nerve function and the production of DNA and red blood cells. The unique feature of Vitamin B12 is its cobalt-containing corrin ring.
- This cobalt ion is critical for B12's biological activity, as it facilitates the transfer of methyl and other groups within cell chemical reactions. - B12 deficiency can lead to serious health problems such as anemia and neurological issues.
Vitamin B12 is not synthesized by plants or animals, but by certain bacteria that live in the soil and the guts of animals, making it an essential nutrient that humans must obtain through dietary sources such as meat, dairy, or fortified foods.

Carboxypeptidase A

Carboxypeptidase A is a type of enzyme known as a metalloenzyme, which suggests that it relies on a metal ion to function effectively. In this case, zinc serves as the critical cofactor for the enzyme's activity.
- This enzyme is primarily involved in protein digestion, breaking down peptide bonds at the end of protein chains to release the individual amino acids. - The zinc ion plays a crucial role in the catalytic mechanism, assisting in the proper positioning of substrate molecules for efficient catalysis.
Carboxypeptidase A is a key player in the complex process of protein digestion and assimilation in the human digestive system, highlighting the importance of metal ions in biological functions.