Introduction to Hemoglobin

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Questions and Answers

What is the primary location where most haemoglobin synthesis occurs before the reticulocyte stage?

Bone marrow

Cytoplasm and mitochondria (correct)

Lung tissue

Liver

What type of structure is haemoglobin considered to be?

Prototypical oligomer

Simple dimer

Heterodimeric tetramer (correct)

Monomeric protein

Which chains are essential for haemoglobin synthesis beyond the embryonic stage?

α chains (correct)

γ chains only

δ chains

β chains only

What is the role of ferrochelatase in the synthesis of haem?

It incorporates iron into haem (B) Signup and view all the answers

Where is haem located in relation to globin chains in haemoglobin?

Toward the periphery of the globin chains (B) Signup and view all the answers

What is the significance of different iron states in haem?

They can affect the final function of the haem molecule (A) Signup and view all the answers

Which statement about haem synthesis is false?

Haem is synthesized primarily in the liver (A) Signup and view all the answers

What other component is necessary for the effective incorporation of iron in haem?

Protoporphyrin IX (A) Signup and view all the answers

Which of the following does not represent a stage of haemoglobin maturation?

Mature lymphocyte stage (D) Signup and view all the answers

What aspect of haemoglobin is primarily altered during its maturation?

The conformation of the protein (B) Signup and view all the answers

What is the primary function of red blood cells in relation to haemoglobin?

Carry O2 from lungs to tissues and CO2 back to lungs (D) Signup and view all the answers

Which measurement is NOT included in the principal haemoglobin measurements reported in the Full Blood Count?

Mean Cell Volume (MCV) (D) Signup and view all the answers

What is the basic structural configuration of haemoglobin?

Heterodimeric tetramer (B) Signup and view all the answers

Which of the following is a correct statement about the composition of the haemoglobin molecule?

It is composed of two alpha-like globin chains and two non-alpha globin chains. (B) Signup and view all the answers

During haemoglobin synthesis, which of these compounds is the starting material to form haem?

Glycine + Succinyl CoA (C) Signup and view all the answers

What is the range for Mean Cell Haemoglobin (MCH)?

27 – 32 pg (D) Signup and view all the answers

Which enzyme is responsible for converting protoporphyrinogen IX to protoporphyrin IX during haem synthesis?

Protoporphyrinogen oxidase (C) Signup and view all the answers

What percentage of cytoplasmic protein in red blood cells is haemoglobin?

98% (D) Signup and view all the answers

What is the role of ferrochelatase in haemoglobin synthesis?

Add iron to protoporphyrin (D) Signup and view all the answers

In the process of haemoglobin synthesis, which compound is produced alongside globin chains?

HMB (D) Signup and view all the answers

Study Notes

Introduction to Haemoglobin

Red blood cells carry oxygen from the lungs to tissues and carbon dioxide back to the lungs
About 98% of the cytoplasm's protein is haemoglobin (Hb)
65% of Hb is produced before the cell nucleus is expelled
Haemoglobin is a metalloprotein

Learning Objectives

Describe the formation of the haemoglobin molecule
Describe the basic structure of haemoglobin
Identify the consequences of specific haemoglobin synthesis defects
Identify haemoglobin measurements within a full blood count (FBC)

Haemoglobin Measurements in FBC

Haemoglobin (Hb)
Mean Cell Haemoglobin (MCH): range 27-32 pg
Mean Cell Haemoglobin Concentration (MCHC): range 315-345 g/L

Basic Structure of Haemoglobin

Haemoglobin is a heterodimeric tetramer
It consists of four globin chains (two alpha and two beta)
It also contains a haem group with an iron molecule

Haemoglobin Synthesis

Haem synthesis involves the chemical reaction of glycine and succinyl CoA, catalysed by ALA synthase
ALA synthase generates amino-laevulinic acid that is used in the subsequent synthesis stages of porphyrin and haem
The synthesis is conducted in the cytoplasm and mitochondria
Iron is incorporated into the haem group by ferrochelatase
Haem is located towards the periphery of the globin chains

Porphyrias

Porphyrias are a group of genetic disorders caused by defects in the haem synthesis pathway
Defects can lead to the accumulation of specific porphyrin precursors in erythrocytes and other tissues

Haem

Iron is chelated into protoporphyrin IX to form the final haem molecule
The iron ion can exist in different states while in the haem molecule

Summary

Most haemoglobin synthesis happens before the reticulocyte stage of maturation
Mature haemoglobin needs the alpha and beta globin chains
Haemoglobin synthesis occurs in the cytoplasm (ribosomes) and mitochondria
Ferrochelatase puts iron into haem subunits
Haem parts are located towards the outside of the globin chains

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Description

This quiz covers the basics of hemoglobin, including its structure, formation, and significance in red blood cells. Learn about hemoglobin measurements in blood counts and the consequences of synthesis defects. Test your knowledge of this essential metalloprotein vital for oxygen transport.