RBC Deficiencies of Carbohydrate Metabolism

Question 1

What is the treatment for metehemoglobinuria?

Answer 1

Methylene blue, vitamin C (ascorbic acid)

Question 2

Most ATP generated by RBCs is used for what purpose?

Answer 2

To power the Na/K pump for ion and H2O transport across the membrane

Question 3

Pyruvate kinase deficiency is an autosomal condition that causes a decrease in ATP production. However, the production of 2,3-BPG is increased. Why is this?

Answer 3

Deficiency of the pyruvate causes a buildup of PEP. This pushes glycolysis backward, ultimately causing a buildup of 1,3-BGP, which is converted to 2,3-BPG.

Question 4

Hexokinase deficiency leads to decreased ATP and NADH production and is rarely seen in clinical practice. Why is the disorder so rare?

Answer 4

Since there is decreased production of ATP and NADH, hexokinase deficiency is generally embryonically fatal as cells cannot live without energy.

Question 5

What are the most common symptoms associated with anemia?

Answer 5

Fatigue, jaundice, paleness, weakness

Question 6

ROS causes the oxidation of hemoglobin to methemoglobin. Why is this so problematic?

Answer 6

In methemoglobin, iron exists in the Fe3+ (ferric state) and the molecule cannot bind O2

Question 7

What enzymatic products are required by RBCs to neutralize ROS?

Answer 7

Glutathione (to reduce methemoglobin) and NADPH (to regenerate glutathione)

Question 8

This enzyme catalyzes the first step of glycolysis.

Answer 8

Hexokinase (glucose –> glucose-6-phosphate)

Question 9

What enzymes are especially important in RBCs to protect against ROS?

Answer 9

Superoxide mutase, catalase, glutathione peroxidase, glutathione reductase

Question 10

What natural agents are known oxidative stressors that should be avoided in patients with G6PD?

Answer 10

Henna, Fava Beans

Question 11

What glycolytic enzyme deficiencies are responsible for causing hemolytic anemia?

Answer 11

Glucose-6-phosphate, pyruvate kinase, hexokinase

Question 12

True/False. G6PD is a severe condition requiring continuous treatment.

Answer 12

False. G6PD is generally asymptomatic, expect during times of oxidative stress.

Question 13

What histological findings are characteristic of G6PD?

Answer 13

Heinz bodies (insoluble masses of proteins) and bite cells (RBCs with Heinz bodies removed by macrophages)

Question 14

What are the consequences of pyruvate deficiency on O2 delivery to tissues?

Answer 14

O2 delivery is actually increased due to increased synthesis of 2,3-BPG

Question 15

G6PD is an X-linked recessive disease that causes hemolytic anemia. What is the pathophysiology?

Answer 15

G6PD is an ezyme of the PPP responsible for producing NADPH. NADPH plays a role in RBC protection against ROS via the glutathione reductase