Hemoglobin Function & Principles of Hemolysis

which state must iron be in, in order to bind to oxygen?

ferrous state (Fe²⁺)

what is the structure of the heme portion of hemoglobin?

four iron atoms surrounded by a porphyrin ring

what is the structure of the globin portion of hemoglobin?

amino acids linked together to form a polypeptide chain

what are the most predominant chains for adult hemoglobin?

alpha and beta

what is the structure of a hemoglobin molecule?

four heme molecules with iron at the center and two pairs of globin chains

at which stage of RBC development does hemoglobin synthesis begin?

polychromatic normoblast

chromosome 11 contains the genes for production of which chains?

epsilon, beta, gamma G and A, and delta

chromosome 16 contains the genes for production of which chains?

alpha and zeta

embryonic hemoglobin gower one contains which chains?

two zeta chains and two epsilon chains

embryonic hemoglobin gower two contains which chains?

two alpha chains and two epsilon chains

embryonic hemoglobin portland contains which chains?

two zeta chains and two gamma chains

fetal hemoglobin F contains which two chains?

two alpha chains and two gamma chains

when is fetal hemoglobin first produced?

3 months of fetal life

when is adult hemoglobin first produced?

3-6 months after delivery

hemoglobin A contains which chains?

two alpha chains and two beta chains

hemoglobin A₂ contains which chains?

two alpha chains and two delta chains

hemoglobin F contains which chains?

two alpha chains and two gamma chains

which percentage of adult hemoglobin is hemoglobin A?

95% to 98%

which percentage of adult hemoglobin is hemoglobin A₂?

3% to 5%

which percentage of adult hemoglobin is hemoglobin F?

less than 2%

when the oxygen dissociation curve is shifted to the left, hemoglobin has a ________ attraction to oxygen and is ________ willing to release it to tissues

higher; less

when the oxygen dissociation curve is shifted to the left, hemoglobin has a ________ attraction to oxygen and is ________ willing to release it to tissues

lesser; more

what is the PO₂ in the lungs?

100 mmHg

what is the percent saturation of hemoglobin in the lungs?

97%

what is the PO₂ in the circulation?

40 mmHg

what is the percent saturation of hemoglobin in the circulation?

75%

in a right-shifted OD curve at 40 mmHg, hemoglobin is ________% more saturated but willing to give up ________% of oxygen to tissue if needed

50; 50

what factors cause a rightward shift of the OD curve?

• anemia

• decreased pH

• increased 2,3-DPG

• elevated body temperature

in a left-shifted OD curve at 40 mmHG, hemoglobin is ________% more saturated but willing to release only ________% to the tissues

75; 12

what factors cause a leftward shift of the OD curve?

• presence of abnormal hemoglobins

• increased pH

• decreased 2,3-DGP

• reduced body temperature

• multiple transfusions of stored blood (lacking 2-3-DGP)

what is methemoglobin?

hemoglobin containing iron which is in the ferric state (Fe³⁺), which is unable to bind to oxygen

what percentage of methemoglobin can cause cyanosis?

10%

what can induce methemoglobin?

aniline drugs or hemoglobin M

what is carboxyhemoglobin?

hemoglobin which has bound to carbon monoxide, which binds to hemoglobin much stronger than oxygen

what is sulfhemoglobin?

hemoglobin with a lower affinity for oxygen which is formed by exposure to sulfonamides or sulfa-containing drugs

what percentage of hemolysis is extravascular?

90%

where does extravascular hemolysis occur?

reticuloendothelial system

what happens to heme and globin contents during extravascular hemolysis?

amino acids of globin chain are recycled into the amino acid pool, and the products of heme are taken through different pathways

how does intravascular hemolysis occur?

RBC’s are lysed directly the blood vessels

what happens to hemoglobin during intravascular hemolysis?

alpha and beta dimers of hemoglobin protein released immediately into the plasma, free hemoglobin binds to haptoglobin

what lab results correspond with extravascular hemolysis?

• decreased Hgb

• decreased Hct

• decreased RBC

• polychromasia in peripheral smear

• increased serum bilirubin

• decreased haptoglobin

• increased LDH

• spherocytes

what lab results correspond with intravascular hemoglobin?

• decreased Hgb

• decreased Hct

• decreased RBC

• increased bilirubin

• decreased haptoglobin

• hemoglobinemia (free hemoglobin)

• hemoglobinuria

• increased reticulocytes

• increased LDH

• schistocytes

which intrinsic blood cell defects can lead to hemolysis?

• structural and synthesis hemoglobinopathies

• RBC membrane defects

• RBC enzyme defects

• stem cell defects

which extrinsic blood cell defects can lead to hemolysis?

• autoimmune hemolytic anemia

• parasite infection

• microangiopathic hemolytic anemia

• environmental agents, including venoms and chemical agents

alpha chains have how many amino acids?

141

beta chains have how many amino acids?

146

which hemoglobin is fetal hemoglobin?

Hgb F

which chemical affects the loading and unloading of oxygen in hemoglobin?

2,3-DPG