Erythrocyte & Reticulocyte Quiz

What does EPO do?

Stimulates BFU-E and CFU-E to differentiate and proliferate into erythrocytes

What is the composition of the red cell membrane?

52% protein

10% lipids

8% carbohydrates

What is the function of integral proteins?

Serve as the backbone of active and passive transport

What are the examples of integral proteins listed in the lesson?

Glycophorins A, B, and C

Band 3 Protein

What is the function of peripheral proteins?

Give the cell its shape, stability, and deformability

What are the examples of peripheral proteins listed in the lesson?

Spectrin

Actin

Ankyrin (band 2.1)

Bands 4.1 and 4.2

Adducin

Dematin

Tropomyosin

What is the function of sialic acid in the red cell membrane?

It is attached to glycophorins A, B, and C; it carries a negative charge that causes the RBCs to repel one another

What is the function of spectrin in the red cell membrane?

It is the predominant skeletal protein; gives the cell its shape and provides structural support

What is the main lipid content of the red cell membrane?

95% of the membrane is either phospholipids or cholesterol

List the functions of red cell metabolism

Maintains the cation pump

Keeps hemoglobin in the reduced form

Maintains high levels of glutathione

Maintains cell flexibility, stability, and deformability

What is the other term for the glycolytic pathway?

The Embden-Meyerhof Pathway (EMP)

What is the purpose of the glycolytic pathway?

Helps the cell maintain its flexibility, stability, and deformity

What is the key enzyme of the glycolytic pathway?

Pyruvate Kinase - Creates ATP by transferring a phosphate group (Pi) from PEP to ADP,

What is the function of the hexose monophosphate shunt?

Keeps hemoglobin in the reduced form (protects from oxidative damage)

What is the key enzyme of the hexose monophosphate shunt?

Glucose-6-phosphate dehydrogenase (G6PD) - Creates NADPH by oxidizing G6P and giving the electrons to NADP+

What are the two products produced by the hexose monophosphate shunt?

NADPH and glutathione

What is the function of the methemoglobin reductase pathway?

Keeps the heme iron in the reduced state (2+)

What is the key enzyme of the methemoglobin reductase pathway?

Methemoglobin reductase - Reduces methemoglobin (3+) into hemoglobin (2+)

What is the function of the Rapaport-Luebering Shunt?

Facilitates the delivery of oxygen and release to the tissues

How does the Rapoport-Luebering shunt facilitates the release of oxygen to the tissues?

It converts 1,3-DPG to 2,3-DPG

Binding of hemoglobin to 2,3-DPG allows release of O2

What happens if there is a deficiency in the HMP?

Buildup of hydrogen peroxide oxidizes hemoglobin, causing it to denature and form Heinz bodies in the RBC.

What happens if there is a deficiency in the methemoglobin reductase pathway?

Methemoglobin builds up, impairing the ability of the RBCs to deliver oxygen

What happens if there is a deficiency in the Rapaport-Luebering shunt?

The RBCs can’t deliver oxygen effectively to the tissues (hypoxia)

What is secondary erythrocytosis and what are causative agents?

A high RBC count that is due to elevated production of EPO.

Caused by:

Anemia

Altitude

Smoking

Heart/lung conditions

Hypoxia

(AASHH)

What is relative erythrocytosis and what can cause it?

An increase in hematocrit without an increase in red cell mass.

Caused by diarrhea, dehydration, and burns

Where does extravascular hemolysis occur?

In the spleen, bone marrow, and liver

During hemolysis, what is hemoglobin broken into?

Globin, iron, and heme

What happens to globin produced during hemolysis?

It is returned to the AA storage pool

What happens to iron produced during hemolysis?

It can become ferritin (for storage) or transferritin (to go to the bone marrow and be incorporated into new RBCs)

What happens to the heme produced during extravascular hemolysis?

It is broken down into biliverdin and CO

The CO goes to the lungs for exhalation

The biliverdin is reduced to bilirubin, combined with albumin, and taken to the liver

What happens to bilirubin once it reaches the liver?

It is conjugated with glucoronic acid (bilirubin diglucoronide) and secreted into the intestines

What happens to conjugated bilirubin once it reaches the intestines?

Intestinal flora change it into urobilinogen or urobilin that is excreted in the feces or reabsorbed and then excreted in the urine

What happens to hemoglobin that is broken down during intravascular hemolysis?

The alpha-beta dimers bind to plasma haptoglobin, which takes the dimer to the liver

What happens if the binding capacity of haptoglobin is exceeded during intravascular hemolysis?

Extra dimers are filtered by the kidneys and excreted in the urine (hemoglobinuria or hemosiderinuria)

What does hemopexin do?

It binds to excess free hemoglobin in the blood (that hasn’t bound to haptoglobin or been excreted) for clearance by the liver

What happens if the binding capacity of hemopexin has been exceeded?

Heme binds with albumin to form methemalbumin for clearance by the liver

Hemoglobinemia

The presence of free hemoglobin in the plasma, usually resulting from intravascular hemolysis

Hemoglobinuria

The presence of free hemoglobin in the urine. Occurs when plasma free hemoglobin exceeds the binding capacity of haptoglobin.

What is the order of heme clearance in intravascular hemolysis?

Haptoglobin → Kidney excretion → Hemopexin → Methemalbumin

What lab results are decreased in both intravascular and extravascular hemolysis?

HGB, HCT, RBCs, and haptoglobin

What lab results are increased in both intravascular and extravascular hemolysis?

Bilirubin, reticulocytes, and LDH

What are two medical findings associated with extravascular hemolysis?

Hepatosplenomegaly

Elevated urobilinogen

What are medical findings associated with intravascular hemolysis?

Hemoglobinemia

Hemoglobinuria

Hemosiderinuria

Methemalbumin

What is the lifespan of a reticulocyte?

It spends 2-3 days in the bone marrow and then 1 day in the periphery before maturing

Why is the reticulocyte count medically relevant?

It helps to determine erythropoietic activity in the bone marrow

Useful for monitoring anemia and responses to therapy

How is RPI calculated?

(Pt HCT/45%) x (Retic %/Retic Maturation Time)

What is the purpose of the RPI?

Looks at if the bone marrow is producing enough RBCs to appropriately compensate for the patient’s degree of anemia.

What is the term for the presence of increased reticulocytes on a Wright-stained PBS when the reticulocyte count is increased?

Polychromasia