Summary for members don't understand Arabic language
Hemoglobin
1. Characteristics—globular protein of four subunits
■ Each subunit contains a heme moiety, which is iron-containing porphyrin.
■ The iron is in the ferrous state (Fe2+), which binds O2.
■ Each subunit has a polypeptide chain. Two of the subunits have α chains and two of the
subunits have β chains; thus, normal adult hemoglobin is called α2β2.
2. Fetal hemoglobin [hemoglobin F (HbF)]
■ In fetal hemoglobin, the b chains are replaced by g chains; thus, fetal hemoglobin is called
α2γ2.
■ The O2 affinity of fetal hemoglobin is higher than the O2 affinity of adult hemoglobin
(left-shift) because 2,3-diphosphoglycerate (DPG) binds less avidly to the γ chains of fetal hemoglobin than to the β chains of adult hemoglobin.
■ Because the O2 affinity of fetal hemoglobin is higher than the O2 affinity of adult hemo-
globin, O2 movement from mother to fetus is facilitated .
3. Methemoglobin
■ Iron is in the Fe3 +
state.
■ does not bind O2.
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