hematologic - hemoglobin disorders Flashcards
Hemoglobin makeup
large molecule
made up of proteins and iron
4 folded chains of globin
an individual erythrocyte may contain about
300 million hemoglobin molecules
Normal hemoglobin beta chain made up of which amino acids
the first 6 amino acids
valine, histidine, leucine, thre, proline, glutamic acid
which amino acid is substituted in sickle cell hemoglobin beta chain
glutamic acid
synthesis of hemoglobin begins in the
proerythroblast and continues through the reticulocyte stage
2 succinyl CoA + 2 glycine yields
pyrrole molecule
4 pyrrole molcules combine to form
protoporphyrin which combines with iron to make heme
hemoglobin A has which subunits?
2 alpha and 2 beta subunits
the type of hemoglobin chain in the hemoglobin molecule determines
the binding affinity for oxygen
the oxygen combining capacity is directly related to
hemoglobin concentration and not on the number of RBCs
in the lungs hemoglobin picks up oxygen which binds to the iron forming
oxyhemoglobin
when oxygen molecules are released at the tissues oxygenated hemoglobin becomes
deoxyhemoglobin
oxygen release depends on
the need for oxygen in the surrounding tissues
shape of the oxy-hemoglobin dissociation curve is ___ and why
sigmoidal due to cooperative binding of oxygen to hemoglobin
RBC lifespan
120 days
how is hemoglobin destroyed?
liver kupffer cell phagocytose the hemoglobin and iron is released back into the blood and carried by transferrin to the bone marrow for production of new RBCs or to the liver to be stored
the porphyrin portion (pyrrole rings) of hemoglobin is converted to
biliverdin and then unconjugated bilirubin is conjugated by hepatocytes and secreted in bile
hemoglobin disorder that has altered affinity
methemoglobin
hemoglobin disorder that is a quantitative disorder of the globin chain
thalaseemia
hemoglobin disorder that is a qualitativev disorder of globin sturctures
sickle cell
methemoglobin is formed when the iron in hemoglobin is
oxidized from the ferrous (Fe2+) to the ferric (Fe3+) state
can methemoglobin bind oxygen?
no so oxygen cannot be carried to tissues
the NADH-dependent enzyme, methemoglobin reductase, is responsible for
converting MHgb back to Hgb
methemoglobin reductase pathway
uses nicotinamide adenine dinucleotide (NADH)-cytochrome b5 reductase in the erythrocyte from anaerobic glycolysis to maintain heme iron in its ferrous state
how does methemoglobin move the oxy-hgb dissociation curve?
moves the curve markedly to the left and therefore delivers little oxygen to the tissues (Left Loves)
symptoms of oxygen deprivation
muscle weakness, nausea, tachycardia