Engineering Chemistry S Datta

ROLE OF METALS IN BIOLOGY 569
Highlights:
• Calcium is mainly concentrated in bones and teeth along with phosphate. Calcium
also plays an important role in all animal cells as intracellular regulator
or messenger.
It helps to regulate the activity of skeletal muscle, heart and many other tissues.
• Magnesium plays an important role in the action of the enzymes of glycolytic
pathway and also in ATP-dependent reactions.
• Copper is essential in the diet since it is involved in the proper utilization of iron,
development of connective tissues and blood vessels.
• Iron is required for the synthesis of haemoglobin, cytochromes etc.
• Zinc is essential for every adult in his diet and acts as the prosthetic group of
about 80 enzymes.
• Nickel, vanadium, chromium and silicon are needed for the proper growth of
bone and connective tissue.
• Selenium is an essential component of glutathione peroxidase.
• Molybdenum is the part of the prosthetic group of xanthine oxidase.
• Some plants have shown requirements for boron and aluminium.
(Cu).
SHORT QUESTIONS AND ANSWERS
Q. 1. What are metalloproteins?
Ans. Proteins which contain metal ions like Fe, Co, Zn, Cu, Mg etc., e.g., ceruloplasmin
Q. 2. What is the difference between metal-activated enzymes and metalloenzymes?
Ans. In metal-activated enzymes the metal is not tightly held by the enzyme and can be
easily exchanged with other cations, e.g., ATPase (Mg 2+ and Ca 2+ ).
In metalloenzymes the metal is held tightly by the enzyme and cannot be readily
exchanged, e.g., xanthine oxidase (Mo).
Q. 3. Which are the principal elements of the body?
Ans. The seven principal elements constitute 60-80% of the body’s inorganic material.
They are Ca 2+ , Mg 2+ , P, Na + , K + , Cl – , S.
Q. 4. What are the factors promoting Ca absorption?
Ans. Vitamin D (calcitrol), parathyroid hormone, low pH (acidic), lactose and amino
acids like lysine and arginine promote Ca absorption.
Q. 5. What is the significance of Ca:P ratio?
Ans. The Ca:P ratio is important for calcification of bones. The product of Ca × P (in
mg/dl) should be around 50 for adults.
Q. 6. What are the biochemical functions of Mg?
Ans. Mg is required for the formation of teeth, it serves as the cofactor for different
enzymes like different kinases and adenylate cyclase. Mg is also required for neuromuscular
functions.