Erythrocyte Biochemistry (Schalm 21)

Question 1

What are clinical signs of inherited deficiency of Band 3 in cattle?

Answer 1

Marked spherocytosis with membrane instability and anemia

Question 2

Name three species and two erythroid stages with high Na+/K+ pump activity

Answer 2

Horse, pig, some ruminants
Nucleated RBC’s and reticulocytes in cats and dogs
(All are high potassium due to pump activity)

Question 3

What dog breeds have high potassium erythrocytes?

Answer 3

Akitas, Jindos, and other East Asian dog breeds (substantial Na/K pump activity)

Question 4

Erythrocytes high in potassium and glutathione concentrations promote replication of what parasite?

Answer 4

Babesia gibsonii

Question 5

What is a suspected role of Stomatin?

Answer 5

This membrane-bound scaffolding protein may modulate other transport proteins

Question 6

Glucose is the major substrate for energy metabolism in erythrocytes of all species except…

Answer 6

The pig (pigs lack functional glucose transporters). Inosine appears to be the major substrate of energy for pig erythrocytes.

Question 7

What enzyme phosphorylates glucose to glucose - 6 - phosphate after entering the cell?

Answer 7

Hexokinase

Question 8

Name the two pathways of glucose metabolism in the mature erythrocyte

Answer 8

Embden-Meyerhof pathway and pentose phosphate pathway

Question 9

What are the major products of the Embden-Meyerhof pathway?

Answer 9

ATP x 2 and lactate x 2

Question 10

What mineral is required for glycolysis through the Embden-Meyerhof pathway?

Answer 10

Phosphate (severe hypophosphatemia can lead to hemolytic anemia)

Question 11

What are the three rate-limiting enzymes in glycolysis in the mature erythrocyte?

Answer 11

Hexokinase
Phosphofructokinase
Pyruvate kinase

Question 12

What are two potential uses for 1,3-diphosphoglycerate in the erythrocyte (produced by the glyceraldehyde phosphate dehydrogenase reaction)

Answer 12

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

Question 13

Name three species with high 2,3DPG concentrations and two species with low concentrations

Answer 13

High: dogs, horses, pigs (man)
Low: cats, ruminants

Question 14

How do 2,3 DPG concentrations affect oxygen affinity?

Answer 14

2,3DPG decreases hemoglobin oxygen affinity

Question 15

How do PFK and PK deficiencies affect 2,3DPG?

Answer 15

PFK deficiencies decrease 2,3DPG (prior step in E-M pathway)
PK deficiencies increase 2,3DPG (later step in E-M pathway)

Question 16

What is the major product of the Pentose Phosphate Pathway?

Answer 16

NADPH

Question 17

Glutathione is importance in protection against…

Answer 17

Oxidative injury

Question 18

Reduced glutathione (GSH) has a highly reactive sulfhydryl group that acts as a …

Answer 18

Nonenzymatic free-radical acceptor to counteract oxidant damage

Question 19

Glutathione reductase reaction is dependent on what two compounds?

Answer 19

FAD (flavin adenine dinucleotide)
NADPH

Question 20

Horses with FAD deficiency display:

Answer 20

Prominent eccentrocytosis
(Reduced GSH concentrations)

Question 21

What enzyme reduces methemoglobin?

Answer 21

Methemoglobin reductase

Question 22

What effect does methylene blue have on methemoglobinemia?

Answer 22

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.

Question 23

FAD is an important cofactor in what two enzyme pathways?

Answer 23

Methemoglobin Reductase (cytochrome B5 reductase)
Glutathione Reductase

Question 24

In the oxygen-hemoglobin dissociation curve, what is represented on the x-axis and y-axis?

Answer 24

X-axis - PO2 (mmHg)
Y-axis - % saturation

Question 25

In the oxygen-hemoglobin dissociation curve, what change in affinity is demonstrated in a shift of the curve to the right?

Answer 25

Decreased oxygen affinity is represented by a rightward shift of the curve

Question 26

Name four factors that decrease hemoglobin oxygen affinity

Answer 26

Increased 2,3DPG Increased CO2 Decreased pH Increased temperature

Question 27

What change in oxygen affinity is represented by a leftward shift in the oxygen-hemoglobin dissociation curve?

Answer 27

An increase in oxygen affinity

Question 28

Name four factors that increase the oxygen affinity of hemoglobin

Answer 28

Decreased 2,3 DPG Decreased CO2 Increased pH Decreased temperature

Question 29

How does 2,3 DPG decrease the oxygen affinity of hemoglobin?

Answer 29

2,3 DPG binds between the two beta-globin chains in hemoglobin, stabilizing the molecule and decreasing the oxygen affinity