1.

The earliest recognizable erythroid precursor on a Wright-stained smear of the bone marrow is:
(Objective 1)

a. pronormoblast

b. basophilic normoblast

c. CFU-E

d. BFU-E

2. This renal hormone stimulates erythropoiesis in the bone marrow: (Objective 4)

a. IL-1

b. erythropoietin

c. granulopoietin

d. thrombopoietin

3. An increase in 2,3-BPG occurs at high altitude in an effort to: (Objective 9)

a. increase oxygen affinity of hemoglobin

b. decrease oxygen affinity of hemoglobin

c. decrease the concentration of methemoglobin

d. protect the cell from oxidant damage

4. The erythrocyte life span is most directly determined by: (Objective 5)

a. spleen size

b. serum haptoglobin level

c. membrane deformability

d. cell size and shape

5. Which of the following depicts the normal sequence of erythroid maturation? (Objective 1)

a. Pronormoblast S basophilic normoblast S polychromatic normoblast S orthochromic normoblast S

reticulocyte

b. Pronormoblast S polychromatic normoblast S orthochromic normoblast S basophilic normoblast S

reticulocyte

c. Basophilic normoblast S polychromatic normoblast S reticulocyte S orthochromic normoblast

S pronormoblast

d. Orthochromic normoblast S basophilic normoblast S reticulocyte S polychromatic normoblast S

pronormoblast
6. The primary effector (cause) of increased erythrocyte production, or erythropoiesis, is: (Objective 4)

a. supply of iron

b. rate of bilirubin production

c. tissue hypoxia

d. rate of EPO secretion

7. An increase in the reticulocyte count should be accompanied by: (Objective 2)

a. a shift to the left in the Hb@O2 dissociation curve

b. abnormal maturation of normoblasts in the bone marrow

c. an increase in total and direct serum bilirubin

d. polychromasia on the Wright's-stained blood smear

8. What property of the normal erythrocyte membrane allows the 7-mcM cell to squeeze through 3-
mcM fenestrations in the spleen? (Objective 5)

a. Fluidity

b. Elasticity

c. Permeability

d. Deformability

9. An increase of erythrocyte membrane rigidity would be predicted to have what effect? (Objective 5)

a. Increase in erythropoietin production

b. Increase in cell volume

c. Decrease in cell life span

d. Decrease in reticulocytosis

10. Extravascular erythrocyte destruction occurs in: (Objective 7)

a. the bloodstream

b. macrophages in the spleen

c. the lymph nodes

d. bone marrow sinuses

Level II

1. Results of a CBC revealed a MCHC of 40 g/dL. What characteristic of the RBC will this affect?
(Objective 2)

a. Oxygen affinity

b. Cell metabolism

c. Membrane permeability

d. Cell deformability

2. If the erythrocyte cation pump fails because of inadequate generation of ATP, the result is:
(Objective 3)

a. decreased osmotic fragility due to formation of target cell

b. formation of echinocytes due to influx of potassium

c. cell crenation due to efflux of water and sodium

d. cell swelling due to influx of water and cations

3. As a person ascends to high altitudes, the increased activity of the Rapoport-Luebering pathway:
(Objective 4)

a. results in precipitation of hemoglobin as Heinz bodies

b. has no effect on oxygen delivery to tissues

c. results in increased release of oxygen to tissues

d. results in decreased release of oxygen to tissues

4. A newborn has a hemoglobin level of 16.0 g/dL at birth. Two months later, a CBC indicates a
hemoglobin concentration of 11.0 g/dL. The difference in hemoglobin concentration is most likely due
to:(Objective 1)

a. chronic blood loss

b. inherited anemia

c. increased intravascular hemolysis

d. physiologic anemia of the newborn

5. A 50-year-old patient had a splenectomy after a car accident that damaged her spleen. She had a
CBC performed at her 6-week postsurgical checkup. Many target cells were identified on the blood
smear. This finding is most likely: (Objective 2)

a. an indication of liver disease

b. a loss of RBC membrane peripheral proteins

c. an abnormal protein to phospholipid ratio of the RBC membrane

d. an accumulation of cholesterol and phospholipid in the RBC membrane

6. Which of the following is necessary to maintain reduced levels of methemoglobin in the

erythrocyte? (Objective 4)

a. Vitamin B6

b. NADH

c. 2,3-BPG

d. Lactate

7. A patient lost about 1500 mL of blood during surgery but was not given blood transfusions. His
hemoglobin before surgery was in the reference range. The most likely finding 3 days later would be:
(Objective 1, 6)

a. increase in total bilirubin

b. increase in indirect bilirubin

c. increase in erythropoietin

d. increased haptoglobin

8. A patient with kidney disease has a hemoglobin of 8 g/dL. This is most likely associated with:
(Objective 6)

a. decreased EPO production

b. increased intravascular hemolysis

c. abnormal RBC membrane permeability

d. RBC fragility due to accumulation of intracellular calcium

9. A laboratory professional finds evidence of Heinz bodies in the erythrocytes of a 30-year-old male.
This is evidence of: (Objective 4)

a. increased oxidant concentration in the cell

b. decreased hemoglobin-oxygen affinity

c. decreased production of ATP

d. decreased stability of the cell membrane

10. A 65-year-old female presents with an anemia of 3 weeks’ duration. In addition to a decrease in
her hemoglobin and hematocrit, she has a reticulocyte count of 6% and 3+ polychromasia on her
blood smear. Based on these preliminary findings, what serum erythropoietin result is expected?
(Objective 6)

a. Decreased
b. Normal

c. Increased

d. No correlation

MLSHC 305. THE ERYTHROCYTES AND HEMOGLOBIN

1. List and describe the stages of erythrocyte maturation in the marrow from youngest to most
mature cells.

Erythrocyte production begins when stem cells, called hemocytoblasts, begin maturation processes.
Hematopoietic stem cells (HSCs) are localized in the medulla of the bone marrow and have a unique
ability to give rise to all the different mature blood cell types and tissues. They are self-renewing
cells. Some Hematopoietic stem cells will differentiate into common myeloid progenitor cells, which
go on to produce erythrocytes, as well as mast cells, megakaryocytes and myeloblasts.

The process by which common myeloid progenitor cells become fully mature red blood cells involves
several stages. These include:

a. Proerythroblast – the erythroblast develops into a proerythroblast, which is only slightly

smaller than the blast, but has a more basophilic cytoplasm. The earliest morphologically
recognizable erythrocyte precursor is the pronormoblast. Each pronormoblast produces
between 8 and 32 mature erythrocytes (a total of 3–5 cell divisions during the maturation
sequence). This cell is the largest of the normoblast series, from 20 to 25 mcM (mm)
b. Basophil erythroblast – forms when the proerythroblast loses its nucleolus.
c. Polychromatophil erythroblast – these have a darkly stained nucleus with a cytoplasm that
stains a grayish-green color due to the accumulation of hemoglobin.
d. Orthochromic erythroblast / Normoblast – in this stage the nucleus becomes smaller and
darker, and the cytoplasm becomes pinker. Nuclear expulsion occurs at the end of this stage
through an asymmetric division; that is the portion that contains the cytoplasm and
organelles becomes the reticulocyte, while the portion containing the nucleus is destroyed
by macrophages.
e. Reticulocytes – contains cytoplasm, cytoplasmic organelles, and many ribosomes. It is
released from the bone marrow and develops into a mature erythrocyte.
f. Mature Erythrocytes – These mature RBCs are released into the bloodstream, where they
survive between 100 to 120 days.

2. Explain the maturation process of reticulocytes and the cellular changes that take place.

Reticulocytes are immature red blood cells that are released into the bloodstream before they are fully
mature erythrocytes. Reticulocytes play a crucial role in replenishing the body's red blood cell supply.
The maturation process of reticulocytes involves several cellular changes, these include:

a. Erythropoiesis is the process by which RBCs are produced. It occurs primarily in the bone
marrow. During this step, Hematopoietic stem cells will differentiate into proerythroblasts, which
then develops into basophilic erythroblasts.
 b. During the Polychromatophilic erythroblasts stage, the developing cells lose their nuclei and
acquire a blue tinge due to the presence of RNA. These cells are larger than mature RBCs and
have a mesh-like network of ribosomes and RNA, giving them a net-like appearance.
c. Reticulocytes undergo a reduction in their organelle content, especially the mitochondria, to
make room for the hemoglobin this is known as Mitochondrial reduction and hemoglobin
synthesis. Hemoglobin synthesis occurs concurrently, leading to an increase in the cellular
hemoglobin content.
d. Loss of organelles and condensation will then take place. That is, the cell will condense and lose
its reticular appearance, transforming into a biconcave disc shape. This process allows the cell to
become more flexible and efficient for gas exchange.
e. After the cellular changes, reticulocytes are released into the bloodstream. Once in circulation,
reticulocytes gradually mature into fully functional erythrocytes over the course of 1-2 days,
during which time the remaining RNA is degraded.

3. Identify the reference interval for reticulocytes.

- Adult/elderly/child: 0.5 - 2%
- Infant: 0.5 - 3.1%
- Newborn: 2.5 - 6.5%

4. Explain the function of erythropoietin, and include the origin of production, bone marrow
effects, and normal values.

Erythropoietin (EPO) is a hormone primarily produced in the kidneys that plays a vital role in stimulating
the production of red blood cells (erythropoiesis) in the bone marrow. It promotes the differentiation
and maturation of erythroid progenitor cells into mature red blood cells, enhancing their oxygen-
carrying capacity. EPO helps maintain the appropriate balance of red blood cells in the body, ensuring
sufficient oxygen transport to tissues and organs. Its regulation is closely tied to oxygen levels, with
increased production in response to low oxygen levels.

EPO is primarily produced in the kidneys, more specifically in the interstitial fibroblasts in the renal
cortex. A small amount of EPO is also produced in the liver. The production of EPO is regulated in
response to the oxygen levels in the body. When the oxygen levels are low, the kidneys sense the
hypoxia (low oxygen) and produce and release more EPO into the bloodstream.

EPO has a direct effect on the bone marrow, where it stimulates the production of red blood cells by
promoting the differentiation of erythroid progenitor cells and supporting their maturation into
erythrocytes. EPO acts on the erythroid progenitor cells, enabling them to survive and proliferate. It also
helps in the maturation of the progenitor cells into mature red blood cells, enhancing their oxygen-
carrying capacity.

The normal levels of EPO in the blood can vary depending on factors such as age, gender, and altitude.
Generally, normal EPO levels are around 4-24 mU/mL.

5. Describe the function of the erythrocyte membrane.

The erythrocyte membrane is a specialized structure that enables red blood cells to perform their
primary function of transporting oxygen and carbon dioxide while maintaining stability, flexibility,
and selective permeability. The erythrocyte membrane serves several crucial functions such as:

- Gas Exchange: It allows for efficient gas exchange, primarily the transport of oxygen (O2)
from the lungs to body tissues and the removal of carbon dioxide (CO2) from tissues to the
lungs. This is facilitated by the unique biconcave shape of red blood cells and the presence of
hemoglobin.
- Flexibility: The erythrocyte membrane is highly flexible, allowing red blood cells to deform
and squeeze through narrow capillaries and small blood vessels without rupturing.
- Stability: It provides structural stability to the cell, helping it maintain its shape and integrity
in the circulation, even when subjected to mechanical stress.
- Surface Area for Gas Exchange: The membrane's large surface area-to-volume ratio
maximizes the area available for gas diffusion, enhancing the efficiency of oxygen and carbon
dioxide exchange.
- Selective Permeability: It regulates the passage of ions and molecules in and out of the cell,
ensuring that essential ions, like potassium, are maintained at the right levels for normal cell
function.
- Blood Group Antigens: The erythrocyte membrane carries specific blood group antigens
(e.g., ABO and Rh antigens), which determine a person's blood type and compatibility for
blood transfusions.
- Immunological Functions: The membrane can interact with components of the immune
system, playing a role in immune responses and antigen recognition.

6. Name the energy substrate of the erythrocyte.

Glucose

7. Define and differentiate intravascular and extravascular red cell destruction.

Intravascular and extravascular red cell destruction are two processes that describe how red blood
cells (erythrocytes) are broken down and removed from circulation in the body.

Intravascular red cell destruction refers to the breakdown of red blood cells that occurs within the
bloodstream itself. The process typically involves the rupture or lysis of red blood cells directly in the
bloodstream. It can occur for various reasons, such as mechanical trauma, complement-mediated
destruction (complement is part of the immune system), or other factors that damage the red blood
cell membrane. That is, when red blood cells lyse within blood vessels, their contents, including
hemoglobin, are released into the plasma. This can lead to complications like hemolysis, where
hemoglobin is released and can cause hemoglobin-related problems, such as kidney damage.

Whereas Extravascular red cell destruction refers to the removal of red blood cells from circulation
by processes occurring outside the bloodstream, primarily within the spleen and liver. In
extravascular destruction, aged or abnormal red blood cells are recognized and phagocytosed
(engulfed and digested) by macrophages, which are immune cells found primarily in the spleen and
liver. Macrophages identify red blood cells that are no longer functioning properly or have
abnormalities, such as damaged membranes or reduced flexibility. The breakdown of red blood cells
 by macrophages in the spleen and liver is a controlled process that helps remove old or damaged
cells from circulation and allows for the recycling of components like iron from hemoglobin. This
process is more efficient and less likely to lead to hemolysis compared to intravascular destruction.

8. State the average dimensions and life span of the normal erythrocyte.

The average erythrocyte is approximately 7-8 um, with a thickness of 2.5um. The typical lifespan of
red blood cells is 120 days.

9. Describe the function of 2,3-BPG and its relationship to the erythrocyte.

2,3-Bisphosphoglycerate is a small molecule that can be found in erythrocytes. Its primary function is to
regulate the binding of oxygen (O2) to hemoglobin, the protein responsible for carrying oxygen in the
blood. It also has a relationship to erythrocytes such as:

a. Oxygen Release: 2,3-BPG binds to hemoglobin in erythrocytes and reduces its affinity for oxygen.
This means that in the presence of 2,3-BPG, hemoglobin is more likely to release oxygen
molecules to the surrounding tissues. This is essential for efficient oxygen delivery to cells
throughout the body.
b. Bohr Effect: 2,3-BPG plays a crucial role in the Bohr effect, which is a phenomenon that helps
deliver oxygen where it’s needed most. When erythrocytes reach tissues with high metabolic
rates (like muscles), they encounter an environment with lower pH (more acidic) and higher
carbon dioxide (CO2) levels. In this acidic and CO2-rich environment, hemoglobin’s affinity for
oxygen decreases even further due to the presence of 2,3-BPG. This encourages the release of
oxygen at the tissues, where it’s needed for cellular respiration.
c. Production and Regulation: Erythrocytes produce 2,3-BPG as a result of glycolysis, a metabolic
pathway that generates energy in the absence of oxygen. The levels of 2,3-BPG are regulated in
response to factors like altitude, exercise, and certain medical conditions. For example, at high
altitudes where oxygen levels are lower, the body can increase 2,3-BPG production to help
enhance oxygen release from hemoglobin.

10. Summarize the mechanisms involved in the regulation of erythrocyte production.

The regulation of erythrocyte (red blood cell) production, a process known as erythropoiesis, is carefully
controlled to maintain the body's oxygen-carrying capacity. Key mechanisms involved in its regulation
include:

a. Hypoxia Detection: One of the primary triggers for erythropoiesis is the detection of low oxygen
levels in the body, a condition known as hypoxia. Specialized cells in the kidneys, called
peritubular interstitial cells, sense reduced oxygen levels in the blood. When oxygen levels drop,
these cells release a hormone called erythropoietin (EPO) into the bloodstream.
b. Erythropoietin (EPO) Production: EPO is the central regulator of erythropoiesis. It is primarily
produced by the kidneys, although a small amount may also come from the liver. EPO stimulates
the proliferation and differentiation of hematopoietic stem cells in the bone marrow, specifically
directing them toward becoming mature erythrocytes.
c. Hematopoietic Stem Cell Differentiation: Under the influence of EPO, hematopoietic stem cells in
the bone marrow differentiate into erythrocyte precursor cells, known as proerythroblasts.
 These precursor cells undergo a series of maturation steps, including the synthesis of
hemoglobin, the red pigment that binds to oxygen.
d. Iron Availability: Adequate iron supply is critical for erythropoiesis since iron is a key component
of hemoglobin. The body regulates iron absorption in the intestines and recycling from old red
blood cells to ensure a steady supply of iron for erythrocyte production.
e. Negative Feedback: As the oxygen-carrying capacity of the blood is restored, the oxygen-
sensitive cells in the kidneys sense higher oxygen levels and reduce EPO production. This
negative feedback loop helps prevent excessive erythrocyte production when it's not needed,
maintaining a balance.
f. Nutritional Factors: Other nutritional factors, such as vitamin B12 and folic acid, are also
essential for erythropoiesis. These vitamins play roles in DNA synthesis and maturation of
erythrocyte precursor cells.
g. Hormonal Regulation: Hormones like testosterone can stimulate erythropoiesis, and their levels
can influence red blood cell production. In contrast, conditions like chronic inflammation can
suppress erythropoiesis.

11. Describe the structure of the erythrocyte membrane, including general dimensions and
features; assess the function of the major membrane components.

The erythrocyte membrane is a specialized structure that allows for the cell's crucial function of
transporting oxygen to various tissues and removing carbon dioxide from the body. It is a selectively
permeable lipid bilayer embedded with various proteins.

The erythrocyte membrane has a biconcave disc shape with an average diameter of approximately 7-8
micrometers and a thickness of 2 micrometers. This unique structure increases the surface area-to-
volume ratio, allowing for efficient gas exchange.

The erythrocyte membrane primarily consists of a lipid bilayer composed of phospholipids, cholesterol,
and glycolipids. These lipids provide structural integrity and fluidity to the membrane. Integral proteins,
such as transmembrane proteins, are embedded within the lipid bilayer. They include band 3 protein,
which functions as an anion exchanger, and glycophorins, which carry blood group antigens and act as
receptors for pathogens. On the inner and outer surfaces are peripheral proteins such as spectrin, actin,
and other cytoskeletal proteins, which provide structural support and maintain the biconcave shape of
the RBC. Glycoproteins and Glycolipids can also be found on the external surface of the membrane. They
are involved in cell recognition, adhesion, and interaction with other cells and molecules in the
bloodstream.

The major functions of the membrane components include:

- Lipid Bilayer: Provides structural integrity and allows the passage of certain molecules in and
out of the cell.
- Integral Proteins: Facilitate ion transport and cell adhesion.
- Peripheral Proteins: Maintain the shape and stability of the cell membrane.
- Glycoproteins and Glycolipids: Contribute to cell recognition, interaction, and immune
response.
 12. Explain the mechanisms used by the erythrocyte to regulate permeability to cations, anions,
glucose, and water.

Erythrocytes, or red blood cells, utilize various mechanisms to regulate the permeability of cations,
anions, glucose, and water. These mechanisms are essential for maintaining the cell's shape, volume, and
overall function. Here's a brief explanation of the regulatory processes:

- Cation Permeability Regulation: The major cation involved in erythrocyte regulation is

potassium (K+). The cell maintains a relatively high intracellular potassium concentration and
a low extracellular concentration. This gradient is maintained by the action of the Na+/K+
ATPase pump, which actively transports potassium into the cell while extruding sodium.
- Anion Permeability Regulation: The major anion regulated by erythrocytes is chloride (Cl-).
Chloride transport is primarily regulated by the band 3 protein, which acts as an anion
exchanger. This protein allows for the exchange of chloride and bicarbonate ions across the
erythrocyte membrane, helping to maintain cellular homeostasis and pH balance.
- Glucose Permeability Regulation: Glucose enters erythrocytes through facilitated diffusion
facilitated by glucose transporters, such as GLUT1. This process is crucial for providing
energy to the cell. Glucose transport into the cell is regulated by the concentration gradient
of glucose across the membrane and the activity of the glucose transporters.
- Water Permeability Regulation: Water permeability is mainly regulated by aquaporins, which
are water channel proteins that facilitate the rapid movement of water across the
membrane in response to osmotic gradients. Aquaporin-1 (AQP1) is the predominant
aquaporin in erythrocytes, enabling efficient water transport across the membrane to
maintain the cell's osmotic balance and prevent excessive swelling or shrinking.

13. Compare and contrast three pathways of erythrocyte metabolism and identify key
intermediates as well as the relationship of each to erythrocyte survival and longevity.

Three main pathways of erythrocyte metabolism include glycolysis, the pentose phosphate pathway, and
the methemoglobin reductase pathway.

Glycolysis is the primary energy-generating pathway in erythrocytes. It involves the breakdown of

glucose to pyruvate, with the concomitant production of ATP. It provides ATP for maintaining erythrocyte
shape, ion transport, and other essential cellular functions. The end products of glycolysis are ATP,
pyruvate, and NADH. The lack of mitochondria in erythrocytes prevents further oxidation of pyruvate in
the citric acid cycle. Glycolysis is crucial for maintaining the high energy demands of the erythrocyte, as
they rely solely on glycolysis for ATP production.

Key Intermediates of glycolysis are Glucose-6-phosphate, fructose-6-phosphate, glyceraldehyde-3-

phosphate, 1,3-bisphosphoglycerate, and pyruvate.

The pentose phosphate pathway on the other hand runs parallel to glycolysis and serves as an alternate
route for glucose metabolism. It generates NADPH, which is critical for protecting erythrocytes from
oxidative stress and maintaining the cell's reduced state. The pathway generates NADPH and ribose-5-
phosphate, which is necessary for nucleotide synthesis. This pathway is essential for protecting
erythrocytes from oxidative damage caused by reactive oxygen species and maintaining the redox
balance within the cell.
Key Intermediates include Glucose-6-phosphate, ribulose-5-phosphate, and NADPH.

And thirdly, The methemoglobin reductase pathway is involved in maintaining the iron within
hemoglobin in the reduced ferrous state (Fe2+), which is crucial for oxygen binding and transport. It
prevents the accumulation of non-functional methemoglobin, which cannot bind oxygen, ensuring
efficient oxygen delivery to tissues. The primary product is the reduction of methemoglobin back to
functional hemoglobin. This pathway is vital for maintaining the oxygen-carrying capacity of
erythrocytes, ensuring effective oxygen transport and preventing conditions such as
methemoglobinemia.

Key Intermediates are Methemoglobin and reduced hemoglobin

14. Generalize the metabolic and catabolic changes within the erythrocyte over time that “label”
the erythrocyte for removal by the spleen.

As erythrocytes age, they undergo various metabolic and catabolic changes that eventually "label" them
for removal by the spleen. The process of senescence (aging) leads to alterations in the structure and
composition of the erythrocyte, which triggers recognition and elimination by macrophages in the
spleen.

a. Loss of Membrane Flexibility: Over time, the lipid bilayer of the erythrocyte membrane becomes
less flexible, resulting in a decrease in deformability. This loss of deformability makes it difficult
for older erythrocytes to traverse the narrow splenic sinusoids.
b. Accumulation of Oxidative Damage: Erythrocytes are constantly exposed to oxidative stress
during their lifespan. As they age, the accumulation of oxidative damage to proteins, lipids, and
other cellular components increases. This oxidative damage can lead to the formation of toxic
products, rendering the erythrocytes more susceptible to removal by the spleen.
c. Decrease in Enzyme Activity: With age, there is a decline in the activity of various enzymes
within the erythrocyte, including those involved in antioxidant defense mechanisms. This
decrease in enzyme activity impairs the cell's ability to counteract oxidative stress and maintain
cellular homeostasis.
d. Loss of Membrane Proteins and Lipids: Aged erythrocytes experience a gradual loss of
membrane proteins and lipids, leading to changes in membrane composition and reduced cell
surface markers. These changes can result in altered recognition by macrophages in the spleen.
e. Alterations in Surface Antigens: During the aging process, erythrocytes may undergo changes in
surface antigens, leading to the exposure of certain markers that are recognized by macrophages
as signals for phagocytosis and removal.

15. Predict the effects of increased and decreased erythropoietin levels in the blood.

Alterations in EPO levels can significantly impact the body's red blood cell production and overall oxygen-
carrying capacity.

Increased Erythropoietin Levels:

- Erythrocytosis: Elevated EPO levels stimulate an increase in red blood cell production,
leading to a condition called erythrocytosis or polycythemia. This can result in an increase in
 the total blood volume and viscosity, potentially leading to complications such as increased
blood pressure, reduced blood flow, and an increased risk of blood clots.
- Improved Oxygen Delivery: Higher EPO levels can enhance the oxygen-carrying capacity of
the blood, improving tissue oxygenation, especially in situations of hypoxia, such as at high
altitudes or in individuals with certain respiratory or cardiovascular conditions.

Decreased Erythropoietin Levels:

- Anemia: Reduced EPO levels can lead to decreased red blood cell production, resulting in
various types of anemia, including those caused by chronic kidney disease, bone marrow
disorders, or nutritional deficiencies. Anemia can lead to symptoms such as fatigue,
weakness, shortness of breath, and pale skin.
- Impaired Oxygen Delivery: Lower EPO levels can result in a decreased ability to generate an
adequate number of red blood cells, leading to reduced oxygen-carrying capacity. This can
adversely affect various organs and tissues, leading to hypoxia and related complications.

16. Diagram the quaternary structure of a hemoglobin molecule, identifying the heme ring, globin
chains, and iron

17. Assemble fetal and adult hemoglobin molecules with appropriate globin chains.
18. Explain how pH, temperature, 2,3-BPG, and PO2 affect the oxygen dissociation curve (ODC).

The oxygen dissociation curve (ODC) represents the relationship between the partial pressure of oxygen
(PO2) and the saturation of hemoglobin with oxygen. Several factors, including pH, temperature, 2,3-
bisphosphoglycerate (2,3-BPG), and PO2, can significantly influence the ODC.

- pH (Bohr Effect): Changes in pH influence the affinity of hemoglobin for oxygen. An increase
in acidity (decrease in pH) results in a rightward shift of the ODC, indicating a decreased
affinity of hemoglobin for oxygen. This shift is known as the Bohr effect. This is particularly
crucial in tissues with high metabolic rates, where increased carbon dioxide production leads
to a decrease in pH, promoting the release of oxygen from hemoglobin for efficient oxygen
delivery.
 - Temperature: Increased temperature leads to a rightward shift in the ODC, indicating a
decreased affinity of hemoglobin for oxygen. This shift is beneficial in tissues with higher
metabolic rates, as they require more oxygen for energy production. Conversely, decreased
temperature promotes a leftward shift, indicating an increased affinity for oxygen, which is
beneficial in the lungs where oxygen uptake is necessary.
- 2,3-BPG (2,3-Bisphosphoglycerate): 2,3-BPG is a byproduct of glycolysis found in
erythrocytes. Increased levels of 2,3-BPG lead to a rightward shift of the ODC, reducing the
affinity of hemoglobin for oxygen. This shift is particularly important in situations of chronic
hypoxia, where it facilitates the release of oxygen from hemoglobin to meet the oxygen
demands of the tissues.
- PO2: PO2 directly affects the saturation of hemoglobin with oxygen. As PO2 increases, the
ODC shows an increase in the saturation of hemoglobin until it reaches a plateau, indicating
the saturation of all available hemoglobin binding sites with oxygen. Higher PO2 levels
promote greater oxygen saturation of hemoglobin, facilitating efficient oxygen transport in
the lungs and oxygen release in the tissues

19. List the types of hemoglobin normally found in adults and newborns and give their
approximate concentration.

In adults and newborns, different types of hemoglobin play essential roles in oxygen transport. Here are
the types of hemoglobin normally found in adults and newborns, along with their approximate
concentrations:

- Adult Hemoglobin (HbA): This is the predominant type of hemoglobin found in adults,
accounting for approximately 95-98% of the total hemoglobin. Adult hemoglobin consists of
two alpha (α) chains and two beta (β) chains (α2β2). It is responsible for the efficient
transport of oxygen throughout the body.
- Fetal Hemoglobin (HbF): Fetal hemoglobin is the main type of hemoglobin found in
newborns. It is present in small amounts in adults, usually less than 1% of the total
hemoglobin. Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin, which
facilitates the transfer of oxygen from the maternal circulation to the fetal circulation
through the placenta.

20. Summarize hemoglobin’s function in gaseous transport

Hemoglobin is a crucial protein found in red blood cells that plays a central role in the transportation of
gases, primarily oxygen and carbon dioxide, throughout the body.

Hemoglobin binds to oxygen in the lungs, where the partial pressure of oxygen is high, forming
oxyhemoglobin. This oxygen-loaded hemoglobin then travels through the bloodstream to deliver oxygen
to tissues and organs throughout the body. The affinity of hemoglobin for oxygen is influenced by factors
such as pH, temperature, 2,3-BPG levels, and the partial pressure of oxygen, ensuring efficient oxygen
release where it is needed most.

Hemoglobin also aids in the transportation of carbon dioxide. Some carbon dioxide is transported
directly by binding to the globin part of hemoglobin, forming carbaminohemoglobin. Additionally,
carbon dioxide is converted to bicarbonate ions in the red blood cells, contributing to the maintenance
of the blood's acid-base balance. The bicarbonate ions are then transported from the tissues back to the
lungs for elimination.

21. Construct a diagram to show the synthesis of a hemoglobin molecule.

22. Describe the ontogeny of hemoglobin types; contrast differences in oxygen affinity of HbF and
HbA and relate them to the structure of the molecule.

The ontogeny of hemoglobin types refers to the developmental changes in the types of hemoglobin
present during different stages of life. In humans, the main types of hemoglobin are fetal hemoglobin
(HbF) and adult hemoglobin (HbA). During embryonic and fetal development, different types of
hemoglobin are sequentially produced, each with specific structural and functional characteristics.

Embryonic Hemoglobin (HbE) is the first type of hemoglobin produced during the embryonic stage,
primarily present during the earliest weeks of gestation.

Fetal hemoglobin is the predominant hemoglobin type during fetal development. It is produced starting
from the embryonic stage and persists throughout gestation until shortly after birth. HbF has a higher
oxygen affinity compared to adult hemoglobin, which is advantageous for facilitating the transfer of
oxygen from the maternal circulation to the fetal circulation through the placenta.

Adult hemoglobin becomes the predominant type after birth, gradually replacing fetal hemoglobin. HbA
consists of two alpha (α) chains and two beta (β) chains. It has a slightly lower affinity for oxygen
compared to HbF, which is beneficial for efficient oxygen unloading in the tissues.

The differences in oxygen affinity between HbF and HbA can be attributed to structural variations in the
globin chains. HbF has gamma (γ) chains instead of beta (β) chains found in HbA. The gamma chains have
a higher affinity for oxygen due to their altered tertiary structure, which results in a stronger binding of
oxygen to the heme groups. This higher affinity allows fetal hemoglobin to extract oxygen from the
maternal circulation more effectively, despite the lower oxygen pressure in the fetal environment. As a
result, HbF aids in ensuring adequate oxygen supply to the developing fetus during gestation.

23. Explain the molecular control of heme synthesis.

The molecular control of heme synthesis involves a complex regulatory network that ensures the
balanced and efficient production of heme in the body. These intricate molecular control mechanisms
ensure that heme synthesis is regulated in response to the body's requirements and environmental
conditions. Understanding the molecular control of heme synthesis is essential for identifying and
managing disorders associated with heme metabolism, such as porphyrias and other related conditions.
Maintaining the delicate balance in the control of heme synthesis is vital for the overall homeostasis and
proper functioning of the body.

- Regulation of Enzyme Activity: The rate-limiting enzyme in heme synthesis, delta-

aminolevulinic acid synthase (ALAS), is tightly regulated. The activity of ALAS is inhibited by
heme itself, preventing excessive heme production. Additionally, factors such as hormonal
and environmental signals can modulate ALAS activity.
- Transcriptional Regulation: Transcription factors, including the heme-regulated eIF2α kinase
(HRI), GATA-1, and nuclear receptors, regulate the expression of genes encoding heme
synthesis enzymes in response to cellular heme levels and external stimuli.
- Post-Transcriptional Regulation: Regulatory RNA-binding proteins and microRNAs modulate
the stability and translation of mRNAs encoding heme synthesis enzymes, further fine-tuning
the overall rate of heme production.
- Feedback Regulation: Heme synthesis is subject to feedback regulation, where the end
product, heme, exerts negative feedback on its own synthesis. Excess heme inhibits the
activity of ALAS and other enzymes in the heme biosynthetic pathway, maintaining heme
production at appropriate levels.
-
24. Given information on pH, 2,3-BPG, CO2, temperature, and HbF concentration; interpret the
ODC, and translate it into the physiologic effect on oxygen delivery.

- Low pH (Acidic Conditions): A decrease in pH (e.g., in metabolically active tissues) shifts the
ODC to the right, indicating a decreased affinity of hemoglobin for oxygen. This promotes
oxygen unloading in the tissues where oxygen is needed, ensuring efficient oxygen delivery
during periods of high metabolic demand (Bohr effect).
- 2,3-BPG: Increased 2,3-BPG Concentration: Elevated 2,3-BPG levels, as seen in conditions like
anemia or chronic hypoxia, shift the ODC to the right. This reduces the affinity of hemoglobin
for oxygen, promoting the release of oxygen in tissues where oxygen levels are low,
improving oxygen delivery.
- CO2: High levels of CO2, which occur in metabolically active tissues, also shift the ODC to the
right. This facilitates oxygen release in these tissues, promoting efficient oxygen delivery.
- Temperature: Increased Temperature: A rise in temperature shifts the ODC to the right,
promoting oxygen release in tissues experiencing increased metabolic activity. This supports
enhanced oxygen delivery to meet the higher demand.
- HbF Concentration: Higher HbF Concentration (in newborns): Fetal hemoglobin (HbF) has a
higher oxygen affinity compared to adult hemoglobin (HbA). A greater concentration of HbF
can shift the ODC to the left, increasing the affinity for oxygen. This allows for efficient
oxygen uptake in the developing fetus and effective oxygen transfer from the maternal
circulation through the placenta.