BIOINORGANIC CHEMISTRY

CSIR NET/JRF Questions

C.PERUMAL, II-M.Sc CHEMISTRY,

SOC-MKU.

1.The ligand system present in vitamin B 12 is

A.porphyrin B.corrinC.phthalocyamine D.crown ether.

• ANSWER:• B.corrin• Explanation• vitamin B12 is a collection of cobalt and corrin

ring molecule which are defined by their particular vitamin function in the body.

• corrin ring similar to porphyrin ring.FOUR of the SIX coordinating sites are provided by corrin ring and a FIFTH by a dimethyl benzimidazole group.the SIX site ,the center of reactivity,is variable.

• porphyrin ring

• corrin ring

2.The red colour of oxyhaemoglobin is mainly due to theA. d-d transitionB. MLCTC. LMCTD. interligand ᴨ-ᴨ*

• ANSWER:• D. interligand ᴨ-ᴨ*

• deoxyhaemoglobin is bluish-purple• Oxyhaemoglobin is red• carboxyhaemoglobin is a cherry red

• The porphyrin around the iron molecule in heme there is a conjugated π-system which could account for the colour.

• The wavelength of light absorbed by hemoglobin exactly corresponds to the the differences in energy

• between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the heme π-system, and are what gives hemoglobin its color.

• To understand the color change, it is important to think about the geometry of the molecule

• O2 does bind, the Fe and O2 orbitals ,bond and their energies change.

• In particular, the O2 π* orbitals interact with the Fe xz and z2 orbitals. A side effect of the π* accepting properties of all three of these ligands .

• Fe is "given up" one of its electrons to the ligand via the ligand's π* orbitals. As a side effect of losing one of its outer electrons, the iron atom is now small enough to align perfectly with heme plane.

3.Superoxide dismutase contains are metal ions1. Zn (II) & Ni (II)2. Cu (II) & Zn (II)3. Ni (II) & Co (III)4. Cu (II) & Fe (III)

• ANSWER:• 2. Cu (II) & Zn (II)• Superoxide dismutase

is an enzyme that alternately catalyzes the dismutation of the superoxide (O2−) radical into either ordinary molecular oxygen (O2) or hydrogen peroxide (H2O2).

4.Carboxypeptidase contains

A. Zn(II) & hydrolysis of CO₂ B. Mg(II) & hydrolyses of CO₂ C. Zn(II) & hydrolyses peptide bonds D. Mg(II) & hrdrolyses peptide bonds

• ANSEWR:• C. Zn(II) & hydrolyses

peptide bonds• EXPLANATION:A carboxypeptidase is a protease enzyme that hydrolyzes (cleaves) a peptide bond at the carboxy-terminal (C-terminal) end of a protein or peptide. (Contrast with an aminopeptidase, which cleaves peptide bonds at the other end of the protein.)

Carboxypeptidase

5.The number of histidine amino acids nitrogen atoms coordinated to bimetallic active sites of oxyhemocyanin & oxyhemerythrine, respectively are

A. 2,3 & 3,3 B. 3,3 & 2,3 C. 3,3 & 2,2 D. 2,4 & 3,2

• ANSWER:• B. 3,3 & 2,3• EXPLANATION:• These two are oxygen

transportor in Antropods.

Oxyhemerythrin

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