Red Blood Cell Structure and Function Quiz

Histidine

Purple

Carbon monoxide (CO)

Nitric oxide (NO)

Store of oxygen for aerobic metabolism

Greater than 95%

120 days

Glycated hemoglobin (HbA1c)

Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Regenerating glutathione (GSH)

Increased bilirubin due to hemolysis

Reduces susceptibility

Storing excess iron in the liver

Inhibition of iron absorption in the GI tract

Hb level below 120 mg/L

Heavy menstrual bleeding

18 mg/day

Transporting iron in the blood

Small, pale red blood cells

Depleted iron stores in the liver

The shape of RBCs is important for maximizing surface area, which is essential for their function in oxygen and CO2 exchange.

Hemoglobin consists of 4 polypeptide chains - 2 alpha and 2 beta, and deficiency in histidine globin chains leads to a decrease in hematocrit and a decrease in Hb Histidine, affecting the synthesis and stability of the heme group.

Different forms of hemoglobin include Oxy-Hb (oxygen bound, red color), Deoxy-Hb (no oxygen bound, darker color), Carboxy-Hb (CO bound), and Carbamino-Hb (CO2 bound to globin).

Myoglobin serves as a store of oxygen in muscle to enable aerobic metabolism. It is essential for providing oxygen to muscle tissues during physical activity.

Oxygen saturation levels (SpO2) should be greater than 95%. If levels fall below 90%, it indicates respiratory distress and potential oxygen deficiency.

Glucose metabolism in erythrocytes is essential for energy production. Hyperglycemia can affect this process, leading to glycosylation of Hb and serving as a biomarker of poor glycemic control.

RBCs circulate for approximately 120 days. High levels of glycemia (>76) can indicate poor glycemic control, potentially impacting the lifespan of RBCs.

The heme group is essential for binding and transporting oxygen. It is synthesized separately and consists of a ring structure of 4 pyrrole N with iron in the center.

G6PD generates NADPH, which regenerates GSH, a major antioxidant that protects the cell.

The causes include decreased dietary iron, inhibition of absorption in the GI tract, increased red cell mass (e.g., during pregnancy), and increased losses such as hemolysis, GI bleeding, and heavy menstrual losses.

The sequential changes include depletion of iron stores, changes in iron transport, defective erythropoiesis, and ultimately iron deficiency anemia.

Decreased ferritin levels indicate decreased iron stores in the body, which is a key indicator of iron deficiency.

Heterozygotes with G6PD deficiency are protected against malaria, while individuals with the deficiency are less susceptible to RBC parasite form mosquito.

Ferritin stores iron in the liver as Fe$^{3+}$ and releases it as Fe$^{2+}$ when needed for heme and hemoglobin synthesis.

The primary losses contributing to iron deficiency anemia include GI bleeding, hemolysis, and heavy menstrual losses.

Transferrin is responsible for transporting iron in the blood, binding to Fe$^{3+}$ and delivering it to cells for various functions such as heme and hemoglobin synthesis.

NADPH is needed to regenerate the redox capacity of the cell and to regenerate glutathione (GSH), a major antioxidant that protects the cell. Insulin resistance may affect the equilibrium of glucose in RBCs, impacting the availability of NADPH.

Heme is catabolized into bilirubin, which is then transported to the liver for further processing. This process is related to iron metabolism as the iron released from heme is stored as Fe$^{3+}$ in ferritin for future use in hemoglobin synthesis.

Iron deficiency anemia can lead to the production of small, pale erythrocytes with decreased energy for neurodevelopment in infants and associated behavioral consequences in children.