Erythrocytes

Question 1

What are 5 general characteristics of RBCs?

Answer 1

• Function to transport oxygen and CO2
• Containers of hemoglobin
• Membrane provides strength and flexibility
• Metabolic apparatus provides energy and protection from environmental insults
• Shape provides deformability

Question 2

Why do men have higher levels affiliated with RBCs than women?

Answer 2

Testosterone increases erythrocyte development

Question 3

What are normal hematocrit levels in men and women?

Answer 3

Men = 39-49%
Women = 33-43%

Question 4

What are normal hemoglobin levels in men and women?

Answer 4

Men = 13.6-17.2
Women = 12.0-15.0

Question 5

What are the main membrane proteins involved in anchoring the RBC cytoskeleton?

Answer 5

Spectrin anchors the actin filaments within the RBC

Ankyrin binds to spectrin and binds to the membrane via band 3

Question 6

How might cells appear if they have problems with their cytoskeletal proteins?

Answer 6

If there is a problem with dimerization, the cells will appear as an elliptocyte; if there is a problem with the proteins themselves, they will appear as spherocytes without biconvacity

Question 7

What three nutritional factors are necessary for maintained red blood cell populations?

Answer 7

Iron
Folate
Vitamin B12

Question 8

Where is iron absorbed and by what proteins?

Answer 8

In the duodenum; hepcidin allows iron to get into enterocytes

Question 9

What compound carries iron in the blood? How do cells acquire iron from it?

Answer 9

Ferritin; it is endocytosed, cleaved from its iron and then excreted back into the blood stream

Question 10

How is iron recycled after red blood cells die?

Answer 10

Macrophages consume red blood cells and cleave iron from hemoglobin

Question 11

Where is iron stored? How would deficiency be diagnosed?

Answer 11

The liver; low serum Fe, high transferrin levels, or low ferritin will indicate anemia

Question 12

Why are Vitamin B12 and folate necessary? How would deficiencies appear?

Answer 12

They are involved in DNA synthesis and methionine resynthesis; erythrocyte precursors divide rapidly and absorb them quickly. A deficiency would present as a patient with macrocytic anemia and hypersegmented neutrophils

Question 13

What are the components that make up hemoglobin?

Answer 13

Globin groups, protoporphyrin, and iron. Iron and protoporphyrin combine to make heme

Question 14

What are the steps involved in the production of protoporphyrin?

Answer 14

succinyl CoA and delta-ALA are transformed in the cytosol to porphobilinogen–>uroporphytinogen–>coproporphyrinogen-
–>proporphyrin (in mitochondria)

Question 15

What are the two most common forms of hemoglobin in adults and their components? What is the most common form in a fetus and its components?

Answer 15

Hemoglobin A (2 alpha and 2 beta) and A2 (2 alpha and 2 delta)
-Hemoglobin F (2 alpha and 2 gamma)

Question 16

What are the two main types of hemoglobin abnormalities? What are their etiologies?

Answer 16

1) Structural variants
2) Thalassemias
- -Most are genetic point mutations, of which there are over 400

Question 17

What is the mechanism of a hemoglobin structural variant?

Answer 17

Alter globin polypeptide without affecting its rate of

synthesis

Question 18

What is the mechanism of a thalassemia?

Answer 18

Decreased synthesis of one or more of the globin chains
Resulting in imbalance in relative amounts of the α & β chains

As a result, the normal chain propagates in excess and precipitates in the cell, ultimately lysing the cell

Question 19

What are the genetic bases of alpha and beta thalassemias?

Answer 19

Alpha tend to be gene deletions

Beta tend to be missense deletions or spice mutations and often manifest as more severe anemias

Question 20

How will most genetic mutations in glycolysis affect red blood cells and why?

Answer 20

Since RBCs do not have any alternate machinery to generate energy, mutations in glycolysis enzymes or in the hexose shunt (which regenerates glutathione) will typically manifest as hemolytic anemia

Question 21

What is the purpose of the Methemoglobin reductase pathway?

Answer 21

It uses NADH to regenerate ferrous iron from ferric iron (Fe++ from Fe+++)

Question 22

What is the purpose of the Luebering-Rappaport pathway?

Answer 22

It draws 1,3 BPG from the glycolysis pathway and transforms it into 2,3 BPG, which is needed for oxygen offloading

Question 23

What is the fate of porphyrin after red blood cell lysis?

Answer 23

It is converted to bilirubin and carbon monoxide and conjugated in the liver to make bile (unconjugated bilirubin is a signal of RBC lysis)

Question 24

What are the N-terminal sugars that determine the ABO antigens?

Answer 24

A- (N-acetylgalactosamine)
B-(D‐galactose)
O-(fucose alone)

Question 25

Why are people incompatible from birth to A or B (or both) antigens?

Answer 25

IgM antibodies to the incompatible blood types are made readily without exposure to blood as those sugars exist as antigens on bacterial and viral substances

Question 26

What are the antigens of the Rhesus factor?

Answer 26

D <—this is the predominant one
Cc,
Ee

Question 27

What are the clinical implications of a Rh incompatibility?

Answer 27

After an Rh negative person is exposed to an Rh+ blood supply, they will readily produce IgG antibodies to it. This can affect transfusions. More commonly presents as hemolytic disease of the newborn where an Rh negative mother is carrying an Rh positive fetus