The oxidation of the Hb molecule's iron ions to the ferric state ...

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The oxidation of the Hb molecule's iron ions to the ferric state (Fe3+) results in which of the fol-lowing?
 
  1. Form of anemia called sickle cell anemia
  2. Formation of methemoglobin (metHb)
  3. Inability of metHb to bind with O2
  a. 1 and 2 only
  b. 1 and 3 only
  c. 2 and 3 only
  d. 1, 2, and 3

Question 2

Which of the following is true regarding fetal hemoglobin (HbF)?
 
  a. It has a reduced level of 2,3-DPG.
  b. It is replaced in the first month of life.
  c. It delivers more O2 to tissues at low PaO2 than normal Hb.
  d. It has a higher P50 than normal Hb.

[sultana.d]

Answer to Question 1

ANS: C
metHb is an abnormal form of the molecule in which the heme-complex normal ferrous iron ion (Fe2+) loses an electron and is oxidized to its ferric state (Fe3+). In the ferric state, the iron ion cannot combine with O2.

Answer to Question 2

ANS: C
HbF has a greater affinity for O2 than does normal adult Hb, as manifested by a leftward shift of the HbO2 curve. Given the low PO2 values available to the fetus in utero, this leftward shift aids O2 loading at the placenta. Because of the relatively low pH of the fetal environment, O2 un-loading at the cellular level is not greatly affected.