Bio-Inorganic Chemistry – Chemistry Optional PYQs (2000–2026)

Here are all 44 Bio-Inorganic Chemistry questions asked in UPSC Chemistry Optional Paper I from 2000 to 2026, arranged under the 2 topics of the official syllabus. Within each topic the latest questions come first.

Each question ends with a code such as [2024/15m/3b] – the year, the marks, the word limit (where UPSC set one) and the question number in the paper.

12.1] Metal ions in biological systems

8 questions

1. What is ‘sodium pump’? Explain the role of sodium pump in biological system. [2024/10m/6c(i)]

2. (i) Why are manganese, iron or cobalt used in redox enzymes in preference to zinc, gallium and calcium? (ii) Explain the emergence of $C{a}^{2+}$, $Z{n}^{2+}$ and $C{u}^{2+}$ in the control of protein folding rather than $A{l}^{3+}$ or $C{r}^{3+}$. (iii) State the characteristics of $Z{n}^{2+}$ that make it suitable as the metal ion in many hydrolytic enzymes. (iv) What features of manganese suit it to function as a redox centre in PS-II as opposed to metals such as copper or nickel? [2020/20m/7c]

3. What is active transport across biological membrane? Propose the mechanism of transport of $N{a}^{+}/K^{+}$ across the membrane. [2019/15m/4a]

4. Why is $C{a}^{2+}$ more suitable than $M{g}^{2+}$ for fast signalling process in cells? [2015/5m/5d(i)]

5. Discuss the role of sodium and potassium in biological processes. Both alkali metals belong to the same group; even though their function is opposite to each other. Why? [2011/15m/5b]

6. Localized accumulation of aluminium in the brain is responsible for Alzheimer’s disease. Why? [2011/10m/7b(ii)]

7. Identify one significant role in biological processes for each of the following elements: Fe, Mg, K, Zn, I. [2008/10m/7b(i)]

8. Explain the role of metal ions in biological systems and their role in ion transport across the cell membrane. [2005/10m/4c]

12.2] Oxygen-uptake proteins, cytochromes and ferredoxins

36 questions

1. What is ferredoxin? How is it classified? [2026/5m/5e]

2. Differentiate between T and R conformation of hemoglobin. [2026/10m/8a]

3. Draw the structure of Ferredoxin protein containing [4Fe – 4S] and find the average oxidation number of iron. [2025/5m/5e]

4. Distinguish the ‘T’ (tense) and ‘R’ (relax) conformations of Hemoglobin on reversible binding of oxygen ($O_2$). [2025/15m/7a]

5. What is the basic difference between Cytochrome ‘b’ and Cytochrome ‘c’? Explain the role of Cytochrome ‘c’ oxidase. [2025/5m/7b]

6. What is Bohr effect? Explain the role of Cytochrome P450. [2024/10m/6c(ii)]

7. Explain the structural and other features of rubredoxin. How does it differ from ferredoxins? [2023/10m/6d]

8. Explain the common structural features of two major iron-containing proteins–haemoglobin and cytochrome c present in the human body. Explain the coordination chemistry involved at the central metal atom in case of oxyhaemoglobin and deoxyhaemoglobin. Give the details of the spin states, magnetic moment and oxidation number of central metal ion in both the cases. [2023/10m/7a]

9. What is allosteric effect? Give example of an allosteric protein. Discuss homotropic allosteric modulators with examples. [2022/10m/5c]

10. Draw the active site structure of Hemocyanin (Hc) in deoxyhemocyanin and oxyhemocyanin forms, and write the colour of Hemocyanin in these two forms. Write the functions of Hemocyanin. [2022/10m/8b]

11. Give the mechanism of fatal formation of hematin in the binding of dioxygen by heme. How can it be averted by living systems? [2021/10m/5c]

12. Draw the structures of various iron-sulphur proteins and their corresponding redox states. [2021/10m/7a]

13. (i) Why are manganese, iron or cobalt used in redox enzymes in preference to zinc, gallium and calcium? (ii) Explain the emergence of $C{a}^{2+}$, $Z{n}^{2+}$ and $C{u}^{2+}$ in the control of protein folding rather than $A{l}^{3+}$ or $C{r}^{3+}$. (iii) State the characteristics of $Z{n}^{2+}$ that make it suitable as the metal ion in many hydrolytic enzymes. (iv) What features of manganese suit it to function as a redox centre in PS-II as opposed to metals such as copper or nickel? [2020/20m/7c]

14. Describe the active site ligand environment around the coordination sphere of each iron in hemerythrin in the oxygenated form. [2019/10m/3b]

15. Draw the active site structure of [2Fe-2S] and [4Fe-4S] ferredoxins. Comment on the oxidation state of metal in oxidised and reduced forms of [2Fe-2S]. [2018/10m/7b]

16. Draw the active site (coordination sphere only) of cytochrome C and cytochrome P-450. Discuss their biochemical function. [2018/15m/8c]

17. Define prosthetic group in cytochromes. How do they differ from haemoglobin? What is their main function? [2017/10m/7b]

18. Describe the important structural features of “Ferredoxin molecule”. What is its role in photosynthesis? [2016/15m/7b]

19. Which metal ions are responsible for decomposition of $H_{2}O$ to $O_2$ during photosynthesis by plants, and what is the nature of this ionic cluster and its ionic state? [2015/5m/5d(ii)]

20. (i) What property/properties of lanthanide $\beta$-diketone complexes make(s) them useful as shift reagents in NMR spectroscopy? (ii) What change in the position of iron in haemoglobin occurs in binding to oxygen and why? [2015/10m/8c]

21. How are iron-proteins classified? What are the various functions performed by iron in biological systems? [2014/10m/6b]

22. (i) What is the co-operative effect of haemoglobin during oxygen transport? (ii) Describe the metal site of Cytochrome C and its function. [2013/20m/6c]

23. What are the functions of carbonic anhydrase and carboxypeptides? Explain. [2012/20m/7c]

24. What molecule is responsible for oxygen transport in molluscs? Give its structure. [2012/15m/7d]

25. (i) Complex formation is an acid-base reaction. Explain with suitable example. (ii) Draw the cis and trans structures of complex diamminedichloroplatinum(II). Which form of the complex is used in the treatment of cancer? (iii) Write a note on cytochromes. [2011/20m/6a]

26. (i) What are prosthetic groups of cytochromes and haemoglobin? (ii) Taking into consideration electron transfer and catalytic function, write in brief on ferrodoxins. [2009/20m/7b]

27. How is iron stored and transported in mammals? What is the oxidation state of iron for storage and transfer? [2008/10m/7b(ii)]

28. Discuss the chemistry of photosynthetic process in green plants. [2007/20m/7a]

29. Draw the structures of cytochromes and ferredoxins explaining their functions in biological systems. [2006/15m/4c]

30. Heme acts as carrier of $O_2$ in the system whereas toxic effects of CO can be explained by replacement reaction. Explain. [2005/20m/5c]

31. Discuss the role of photosynthesis in ferrodoxin molecule and describe its structural features. [2005/10m/6c]

32. Describe the photosyntheic process and the role of cytochrome C. [2004/20m/7c]

33. Describe the important structural features of ferrodoxin molecule. What is its role in photo-synthesis? [2003/20m/6c]

34. Explain in vivo and in vitro fixation of nitrogen. [2002/20m/5c]

35. Explain the phosphorescent behaviour of chlorophyll and the significance of cytochromes. [2002/20m/5d]

36. Give the mechanism of electron transfer reactions in Ferredoxin $F{e}_2{S}_2$. [2001/20m/8a]

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Last updated: 30 October 2026