Haematology Lecture 3: Haemoglobin

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Questions and Answers

What is the primary function of the iron atom in each haem group of haemoglobin?

To bind oxygen molecules (correct)

To provide structural support to the polypeptide chains

To catalyze the breakdown of haemoglobin

To bind with electrons for energy transfer

Which of the following statements correctly describes a characteristic of haemoglobin?

It consists of three polypeptide chains and a haem group

It binds to carbon dioxide instead of oxygen

It lacks any iron components

It exhibits co-operative binding (correct)

How many total binding sites are available on the iron atom in each haem group of haemoglobin?

4 binding sites

5 binding sites

6 binding sites (correct)

7 binding sites

Which type of haemoglobin is most commonly discussed in the context of normal physiology?

Adult haemoglobin Signup and view all the answers

What aspect of haemoglobin is primarily affected in anaemia?

The amount of iron available for binding Signup and view all the answers

What defines anaemia in men according to the World Health Organization?

Less than 7.7 mmol/l (13 g/dl) Signup and view all the answers

Which type of haemoglobinopathy involves chains produced in decreased amounts?

Beta thalassemia Signup and view all the answers

What is a consequence of sickle cell disease?

Intense pain due to obstruction Signup and view all the answers

Which haemoglobin variant is characterized by a single amino acid substitution?

Haemoglobin S Signup and view all the answers

What was the RBC count in the provided case study?

3.71 x 10^12/L Signup and view all the answers

What is the significance of the sickle cell trait in individuals?

Provides resistance against malaria Signup and view all the answers

What is the MCV value indicative of microcytic anaemia in the case study?

56.2 fL Signup and view all the answers

What might pale skin in a patient indicate?

Potential anaemia Signup and view all the answers

What is the primary function of haemoglobin in the blood?

To carry oxygen from the lungs to tissues Signup and view all the answers

Which type of haemoglobin makes up the majority of adult haemoglobin?

Haemoglobin A Signup and view all the answers

How much oxygen can 1 gram of haemoglobin carry?

1.34 ml Signup and view all the answers

What is the significance of cooperative binding in haemoglobin?

It enables the binding of a greater number of O2 molecules due to conformational changes. Signup and view all the answers

Which type of haemoglobin has the highest affinity for oxygen?

Foetal haemoglobin Signup and view all the answers

At what oxygen saturation level are the haem groups in haemoglobin fully occupied by oxygen?

100% Signup and view all the answers

What is the role of the Gower-1 and Gower-2 embryonic haemoglobins?

To transport oxygen in fetuses Signup and view all the answers

Which statement best describes deoxyhaemoglobin?

It occurs after oxyhaemoglobin releases O2. Signup and view all the answers

Study Notes

Haematology Lecture 3: Haemoglobin

Haemoglobin (Hb) structure comprises four polypeptide chains, each bound to a haem group. An iron (Fe²⁺) atom is centrally located in each haem group.
Hb's function is oxygen transport. Haemoglobin's structure is adapted to loading and unloading oxygen.
Different types of haemoglobin exist, including HbA (the predominant type in adults), HbA2, and foetal haemoglobin (HbF). HbF has a higher affinity for oxygen than HbA, aiding oxygen transfer from the mother to the foetus.
Embryonic haemoglobin types (Gower 1 and Gower 2, Portland 1 and Portland 2) are present during foetal development, switching to HbF and then HbA.
Normal haemoglobin levels vary between men (7.7 mmol/L or 13 g/dL) and women (7.4 mmol/L or 12 g/dL).
Haemoglobin abnormalities, including haemoglobinopathies, can lead to conditions like anaemia and reduced oxygen-carrying capacity. An example of a significant haemoglobin abnormality is HbS.
HbS results from a single amino acid substitution (valine for glutamic acid) in the β-globin chain.
This substitution causes HbS to form long fibrous structures under low oxygen conditions, causing red blood cell sickling.
Sickle cell trait provides a degree of protection against malaria.

Co-operative Binding

Binding of one oxygen molecule to haemoglobin increases the affinity of subsequent oxygen molecules for binding.
This "co-operative binding" maximizes oxygen uptake in the lungs and facilitates oxygen release in tissues.

Haemoglobin Breakdown

Old or damaged red blood cells (RBCs) are destroyed by macrophages in the spleen.
Haemoglobin is broken down into its components – globin (amino acids) and haeme.
Iron from haeme is recycled for new haemoglobin synthesis.
Biliverdin and then bilirubin (a yellow pigment) are formed from haeme and transported to the liver for processing and excretion in bile.
Bilirubin build-up can result in jaundice.

Abnormal Haemoglobin Production: Haemoglobinopathies

Approximately 5% of the global population carries globin variants.
Inherited disorders often lead to abnormal haemoglobin production (e.g. thalassemias, HbC, HbE).
Thalassemia is characterized by reduced or absent production of either α- or β-globin chains.
Other abnormal polypeptide chains like HbC, E, I, J, S are also present.

Case Study (Example)

A 75-year-old female presented with shortness of breath and fatigue.
Physical examination revealed pale skin.
Complete blood count (CBC) results: RBC 3.71 x 10¹²/L, HGB 5.9 g/dL, HCT 20.9%, MCV 56.2 fL, MCH 15.9 pg, MCHC 28.3 g/dL, WBC 5.9 x 10⁹/L, Neutrophils 82%, Lymphocytes 13%, Monocytes 1%, Eosinophils 4%, Basophils 0%, and Platelets 383 x 10⁹/L.
Iron profile showed low ferritin (<10 ng/mL), serum iron (24 µg/dL), Total Iron Binding Capacity (TIBC) 729 µg/dL, and low transferrin saturation (3%).

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Description

Explore the intricate structure and function of haemoglobin (Hb) in this quiz based on Lecture 3 of Haematology. Understand the different types of Hb, their developmental transitions, and the implications of various haemoglobinopathies. Assess your knowledge of Hb's role in oxygen transport and its importance in human health.