hemo 6

Flashcards covering hemoglobin structure and function, synthesis, normal adult Hb types and percentages, oxygen dissociation curve shifts, and extravascular vs intravascular hemolysis as described in the notes.

What are the components of hemoglobin?

A tetramer consisting of 4 globin chains (2 alpha and 2 non-alpha) and 4 heme groups, each containing iron capable of binding oxygen.

What are the globin chains and their expression patterns?

Alpha chains are expressed throughout life; beta chains after birth; gamma chains during fetal development; delta chains are a minor adult chain.

Where are globin chains synthesized?

In the ribosomes of erythroid precursors (cytoplasm of developing red blood cells).

Where are the globin gene loci located?

Alpha-globin genes on chromosome 16; beta-globin gene on chromosome 11.

What is the function of hemoglobin?

Oxygen transport, carbon dioxide transport, and buffering to regulate blood pH.

What factors affect oxygen binding to hemoglobin?

Cooperative binding; affected by pH, CO2, temperature, and 2,3-bisphosphoglycerate (2,3-BPG).

Where does extravascular hemolysis occur and why?

Primarily in the spleen, with possible involvement of the liver and bone marrow, due to macrophage clearance of damaged RBCs.

What is the mechanism of extravascular hemolysis?

Macrophages phagocytose damaged or abnormal red blood cells.

What are the typical lab findings in extravascular hemolysis?

Increased indirect bilirubin, increased LDH, decreased haptoglobin; spherocytes on smear; no free hemoglobin in plasma or urine.

Which conditions are commonly associated with extravascular hemolysis?

Hereditary spherocytosis, autoimmune hemolytic anemia, and certain hemoglobinopathies.

Where does intravascular hemolysis occur and which organs are affected?

Within blood vessels; affects the circulatory system and kidneys.

What is the mechanism of intravascular hemolysis?

RBCs rupture and free hemoglobin is released into plasma (hemoglobinemia).

What are the typical lab findings in intravascular hemolysis?

Decreased haptoglobin, increased free plasma hemoglobin, hemoglobinemia and hemoglobinuria, increased LDH; schistocytes on smear.

Which conditions can cause intravascular hemolysis?

G6PD deficiency, DIC, TTP, HUS, paroxysmal nocturnal hemoglobinuria, and mechanical (prosthetic valve) damage.

Where does hemoglobin synthesis begin in erythroid precursors?

Protoporphyrin synthesis occurs in mitochondria; iron (Fe2+) is incorporated to form heme in mitochondria.

Where is globin chain synthesis carried out?

In the cytoplasm of developing erythroid precursors.

How are hemoglobin molecules finally formed?

Heme combines with globin chains to form functional hemoglobin.

What are the normal adult hemoglobins and their roles?

HbA (main adult, α2β2); HbA2 (minor adult, α2δ2); HbF (fetal, α2γ2).

What are the typical percentages of HbA, HbA2, and HbF in adults?

HbA ~95–98%; HbA2 ~2–3%; HbF ~0.2–1% (HbF predominates in fetal life and at birth).

What factors cause a right shift in the oxygen-hemoglobin dissociation curve?

Increased CO2 (Bohr effect), increased temperature, increased 2,3-BPG, exercise, and anemia.

What factors cause a left shift in the oxygen-hemoglobin dissociation curve?

Decreased CO2, decreased temperature, presence of HbF, and carbon monoxide poisoning increases Hb affinity (left shift).

What bone marrow change occurs during hemolysis?

Increased erythropoiesis (erythroid hyperplasia).

What smear findings indicate extravascular hemolysis?

Polychromasia and spherocytes.

What smear findings indicate intravascular hemolysis?

Schistocytes.

What plasma changes accompany hemolysis?

Hemoglobinemia and hemoglobinuria; decreased haptoglobin; free hemoglobin in plasma.