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Biochemistry

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Vitamins, Harmones and Hemoglobin

Question
66 out of 82
 

False statement about haemoglobin structure



A Hb has 2 polypeptide

B Iron is present in ferrous state

C Hb structurally similar to myoglobin

D Ferrous ions are in porphyrin rings

Ans. A Hb has 2 polypeptide

Structure of the Hb: Total no of Amino acid = 574 (Each chain = 146)

a. Tetramer, (4-polypeptides chain 2α and 2 β subunits) mol. Wt = 6.4450, contains heme as prosthetic group.

b. 4 gm of iron per mole of Hb in Fe state (ferrous)

c. Porphyrins- tetra pyrrole structure - Linked with methylene bridges or methylidyne bridges

d. Iron in ferrous state (Fe is bound to the nitrogen atom of the pyrrole rings.

e. Iron is also linked internally (linkage) to the nitrogen of the imidazole ring of the histidine of the

polypeptide.

f. The propionic acid at 6th and 7th position of heme of III and IV pyrroles.

g. Vinyl is attached to I and II rings.

h. Hb molecule and its subunits contain mostly Hydrophobic amino acids internally and Hydrophilic amino acid on their surface so they form “Heme pockets”

i. In heme pocket, α-subunits are of size necessary for entry of O2 molecules but the entry of O2 molecule in β-subunits is blocked by valine residues.

Myoglobin contains Heme (cyclic tetrapyrrole as prosthetic group, single polypeptide, of mol. Wt — 17,000, rich in α-helix, surface is polar and interior is non polar. Iron in ferrous state, binds O2 Histidine F8 and F7 perform unique role in O2 binding.

Vitamins, Harmones and Hemoglobin Flashcard List

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