Hemoglobin Overview and Functions

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Questions and Answers

What is the primary function of hemoglobin in red blood cells?

Regulate blood pressure

Provide structural support to the cell

Carry carbon dioxide to the lungs

Carry oxygen to the tissues (correct)

What stimulates hemoglobin production in the body?

Tissue hypoxia (correct)

Increased oxygen levels in blood

High iron levels

Decreased red blood cell count

Which of the following components are synthesized in the mitochondria of red blood cell precursors?

Carbon dioxide

Oxygen

Globin chains

Heme groups (correct)

What percentage of hemoglobin is synthesized during the reticulocyte stage of red blood cell development?

35% Signup and view all the answers

What are the two main components of hemoglobin?

Heme and globin Signup and view all the answers

In adults, what is the reference range of hemoglobin for males in grams per deciliter?

14-17.4 g/dL Signup and view all the answers

What is the role of transferrin in hemoglobin synthesis?

It delivers iron to reticulocytes Signup and view all the answers

What is the molecular weight of hemoglobin approximately?

64,000 Signup and view all the answers

What is the correct chain designation for the beta globin gene?

β Signup and view all the answers

Which statement accurately describes the embryonic hemoglobin Gower 1?

It is composed of two zeta and two epsilon globin chains. Signup and view all the answers

How does the rate of globin synthesis relate to porphyrin synthesis?

Globin synthesis is proportional to porphyrin synthesis. Signup and view all the answers

What happens to the iron in methemoglobin?

It is in the ferric (Fe3) state. Signup and view all the answers

Which type of hemoglobin is formed when oxygen molecules are replaced by carbon monoxide?

Carboxyhemoglobin Signup and view all the answers

What distinguishes sulfhemoglobin from other types of hemoglobin?

It contains sulfur. Signup and view all the answers

What is the primary component of adult hemoglobin A?

alpha(2), beta(2) Signup and view all the answers

At what percentage does hemoglobin A typically occur in adults?

~95% Signup and view all the answers

Study Notes

Hemoglobin Definition

Hemoglobin is a specialized conjugated protein.
It has a molecular weight (M.W) of 64,000.
It is the oxygen-carrying protein in red blood cells (RBCs).
Each RBC contains approximately 640 million hemoglobin molecules.
These molecules make up about 60% of the dry weight of a red blood cell.

Hemoglobin Structure

Hemoglobin consists of four polypeptide subunits.
Each subunit includes a heme group.
The heme group has a porphyrin ring and ferrous iron.
Hemoglobin has two alpha chains and two beta chains.

Hemoglobin Function

Hemoglobin carries oxygen from the lungs to the body tissues.
It removes carbon dioxide (CO2) from the tissues.
Hemoglobin helps maintain blood pH by acting as a buffer. This is because it changes from oxyhemoglobin (carrying oxygen) to deoxyhemoglobin (without oxygen).

Hemoglobin Synthesis

Hemoglobin synthesis occurs in the mitochondria of developing red blood cells as they mature in the bone marrow.
Adequate iron supply and delivery is crucial for normal synthesis.
Adequate synthesis of protoporphyrins is important.
Adequate globin synthesis is essential for normal function.
65% of hemoglobin is synthesized in erythroblasts, with 35% produced in reticulocytes.
Hemoglobin synthesis occurs primarily in the mitochondria, while globin production occurs in the polyribosomes.
The rates of haem and globin synthesis are precisely coordinated for optimal hemoglobin assembly.
Iron delivery and supply is required. Iron is delivered to reticulocytes via transferrin.
Protoporphyrins are synthesized in the mitochondria of red blood cell precursors, a process that requires EPO (erythropoietin), vitamin B6.
Protoporphyrin + iron = heme.
Globin synthesis depends on genes and the precise amino acid order in the globin chains.
The synthesis of globins is genetically controlled.
Humans have two clusters of globin-gene clusters in chromosome 11 (beta-like) and chromosome 16 (alpha-like).

Hemoglobin Reference Ranges

Adult males have hemoglobin levels between 14 and 17.4 g/dL.
Adult females have hemoglobin levels between 12 and 16 g/dL.
Newborn babies have hemoglobin levels between 13.5 and 20.0 g/mL.
Children aged 6-12 have hemoglobin levels between 11.5 and 15.5 g/mL.

Normal Hemoglobins

Embryonic hemoglobins include Gower 1 (zeta 2, epsilon 2), Gower 2 (alpha 2, epsilon 2), and Portland (zeta 2, gamma 2).
Fetal hemoglobin (HbF) is alpha 2, gamma 2.
Adult hemoglobin (HbA) is alpha 2, beta 2.

Oxygen Transport

The amount of oxygen bound to hemoglobin and released to tissues depends on the partial pressures of oxygen (PO2) and carbon dioxide (PCO2).
Oxyhemoglobin is hemoglobin with oxygen.
Deoxyhemoglobin is hemoglobin without oxygen.
Oxygen affinity is the ease with which hemoglobin binds and releases oxygen.

Oxygen Affinity

Oxygen affinity affects the proportion of oxygen released to tissues at a given oxygen pressure.
Increased oxygen affinity means hemoglobin has a stronger attraction to oxygen, binding more.
Decreased oxygen affinity causes oxygen to be released more easily

Oxygen Dissociation Curve

A right-shift in the oxygen dissociation curve shows hemoglobin with less attraction to oxygen, and is more readily released to tissues.
Factors that shift the curve to the right include anemia and acidosis.
A left-shift shows greater attraction between hemoglobin and oxygen and is less readily released to the tissue.
Examples that shift the curve to the left include abnormal hemoglobins and alkalosis,

Carbon Dioxide Transport

Three mechanisms are involved in CO2 transport: dissolution in plasma, formation of carbonic acid, and binding to carbaminohemoglobin.

Nonfunctional Hemoglobins

Nonfunctional hemoglobins include carboxyhemoglobin, methemoglobin, and sulfhemoglobin.
In carboxyhemoglobin case, oxygen molecules are replaced by carbon monoxide.
In methemoglobin, iron in hemoglobin is in the ferric state instead of the ferrous state, which prevents oxygen binding.
Sulfhemoglobin has sulfur in the hemoglobin molecule and cannot revert to oxyhemoglobin.

Normal Red Blood Cell Breakdown

Aged or damaged red blood cells are broken down.
Hemoglobin is broken down into heme and globin components.
Heme is further broken down to iron, protoporphyrin, and CO.
Globin is broken down into amino acids.
Iron is recycled and reused.
Bilirubin is produced from protoporphyrin and processed by the liver.
Excess bilirubin is excreted in the feces (stercobilin) and urine (urobilinogen).

What Happens to Aged Red Blood Cells

Aged red blood cells are broken down by macrophages.
The globin part of hemoglobin is broken down into amino acids, reused for protein synthesis.
The iron part is released and stored in transferrin
The heme portion is broken down into biliverdin, then bilirubin, which is processed by the liver and eventually eliminated in bile.

Hemoglobin Abnormalities

There are primarily two types of hemoglobin abnormalities:
Quantitative abnormalities (e.g. thalassemia). These involve reduced production of specific globin types.
Qualitative abnormalities (e.g. sickle cell anemia). These cause abnormal hemoglobin.

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Explore the structure, function, and synthesis of hemoglobin in this informative quiz. Understand how this crucial protein facilitates oxygen transport and maintains blood pH levels. Delve into the specifics of its molecular composition and biological significance.