Erythrocyte Biochemistry (Schalm 21) Flashcards
What are clinical signs of inherited deficiency of Band 3 in cattle?
Marked spherocytosis with membrane instability and anemia
Name three species and two erythroid stages with high Na+/K+ pump activity
Horse, pig, some ruminants
Nucleated RBC’s and reticulocytes in cats and dogs
(All are high potassium due to pump activity)
What dog breeds have high potassium erythrocytes?
Akitas, Jindos, and other East Asian dog breeds (substantial Na/K pump activity)
Erythrocytes high in potassium and glutathione concentrations promote replication of what parasite?
Babesia gibsonii
What is a suspected role of Stomatin?
This membrane-bound scaffolding protein may modulate other transport proteins
Glucose is the major substrate for energy metabolism in erythrocytes of all species except…
The pig (pigs lack functional glucose transporters). Inosine appears to be the major substrate of energy for pig erythrocytes.
What enzyme phosphorylates glucose to glucose - 6 - phosphate after entering the cell?
Hexokinase
Name the two pathways of glucose metabolism in the mature erythrocyte
Embden-Meyerhof pathway and pentose phosphate pathway
What are the major products of the Embden-Meyerhof pathway?
ATP x 2 and lactate x 2
What mineral is required for glycolysis through the Embden-Meyerhof pathway?
Phosphate (severe hypophosphatemia can lead to hemolytic anemia)
What are the three rate-limiting enzymes in glycolysis in the mature erythrocyte?
Hexokinase
Phosphofructokinase
Pyruvate kinase
What are two potential uses for 1,3-diphosphoglycerate in the erythrocyte (produced by the glyceraldehyde phosphate dehydrogenase reaction)
1) Utilization by the phosphoglycerate kinase reaction to make ATP in the E-M pathway
2) Conversion to 2,3 DPG by the diphosphoglycerate mutase reaction
Name three species with high 2,3DPG concentrations and two species with low concentrations
High: dogs, horses, pigs (man)
Low: cats, ruminants
How do 2,3 DPG concentrations affect oxygen affinity?
2,3DPG decreases hemoglobin oxygen affinity
How do PFK and PK deficiencies affect 2,3DPG?
PFK deficiencies decrease 2,3DPG (prior step in E-M pathway)
PK deficiencies increase 2,3DPG (later step in E-M pathway)
What is the major product of the Pentose Phosphate Pathway?
NADPH
Glutathione is importance in protection against…
Oxidative injury
Reduced glutathione (GSH) has a highly reactive sulfhydryl group that acts as a …
Nonenzymatic free-radical acceptor to counteract oxidant damage
Glutathione reductase reaction is dependent on what two compounds?
FAD (flavin adenine dinucleotide)
NADPH
Horses with FAD deficiency display:
Prominent eccentrocytosis
(Reduced GSH concentrations)
What enzyme reduces methemoglobin?
Methemoglobin reductase
What effect does methylene blue have on methemoglobinemia?
Methylene blue is reduced to leucomethylene blue by NADPH-dependent diaphorase activity. This leucomethylene blue reacts spontaneously with methemoglobin, reducing it to Hgb and regenerating methylene blue.
FAD is an important cofactor in what two enzyme pathways?
Methemoglobin Reductase (cytochrome B5 reductase)
Glutathione Reductase
In the oxygen-hemoglobin dissociation curve, what is represented on the x-axis and y-axis?
X-axis - PO2 (mmHg)
Y-axis - % saturation
In the oxygen-hemoglobin dissociation curve, what change in affinity is demonstrated in a shift of the curve to the right?
Decreased oxygen affinity is represented by a rightward shift of the curve
Name four factors that decrease hemoglobin oxygen affinity
Increased 2,3DPG
Increased CO2
Decreased pH
Increased temperature
What change in oxygen affinity is represented by a leftward shift in the oxygen-hemoglobin dissociation curve?
An increase in oxygen affinity
Name four factors that increase the oxygen affinity of hemoglobin
Decreased 2,3 DPG
Decreased CO2
Increased pH
Decreased temperature
How does 2,3 DPG decrease the oxygen affinity of hemoglobin?
2,3 DPG binds between the two beta-globin chains in hemoglobin, stabilizing the molecule and decreasing the oxygen affinity
