What is the Difference Between Ferritin and Hemoglobin

The key difference between ferritin and hemoglobin is that ferritin is an intracellular storage metalloprotein that stores the iron and releases it in a controlled manner, while hemoglobin is a transport metalloprotein in red blood cells that transports oxygen through the body.

Ferritin and hemoglobin are two important metalloproteins. Metalloproteins are proteins that have a metal ion cofactor. These metallic elements can be iron, copper, cobalt, manganese, etc. A large proportion of proteins belong to this group. For example, there are around 3000 zinc metalloproteins in humans. Therefore, metaproteins have many functions in the cells, including storage, transport, enzymes, signal transduction proteins and defence proteins against infections.

CONTENTS

1. Overview and Key Difference
2. What is Ferritin 
3. What is Hemoglobin
4. Similarities – Ferritin and Hemoglobin
5. Ferritin vs Hemoglobin in Tabular Form
6. Summary – Ferritin vs Hemoglobin

What is Ferritin?

Ferritin is a universal intracellular storage metalloprotein that stores iron and releases it.  This protein is present in almost all living organisms, including archaea, bacteria, algae, higher plants, and animals. Therefore, it is the primary iron storage protein in prokaryotes and eukaryotes. Structurally, ferritin is a globular protein that contains 24 protein subunits. The ferritin that is not combined with iron is known as apoferritin. The molecular mass of this protein is 474 kDa. The genes encoding for this protein in humans are FTL and FTH.

Ferritin can keep the iron in soluble and non-toxic form. It is a very important buffer against iron deficiency and iron overload in humans. Ferritin is a cytosolic protein in many tissues. However, a small amount is secreted into the serum, so it can act as an iron carrier. Doctors take serum ferritin as an indirect marker of the total amount of iron stored in the body. Hence, serum ferritin testing is used as a diagnostic test for iron deficiency anemia. The normal ferritin level in the blood for men is 18-270 ng/mL, while for women, it is 30-160 ng/mL. Moreover, ferritin has many useful functions such as iron storage, iron carrier, ferroxidase activity, role in immune and stress responses, participation in oxidation and reduction reactions, etc.

What is Hemoglobin?

Haemoglobin is a transport metalloprotein in red blood cells that transports oxygen through the body. It contains irons and presents in almost all vertebrates as well as some invertebrates. The hemoglobin carries oxygen from the lungs or gills to the rest of the body. Then it releases oxygen for aerobic respiration in order to produce energy for the functions of organisms. Normally, a healthy individual has 20-30 grams of hemoglobin in every 100 mL of blood. Mammalian hemoglobin can carry up to four oxygen molecules.  Hemoglobin has an oxygen-binding capacity of 1.34 mL O₂ per gram. Furthermore, hemoglobin is also involved in the transport of other gases such as CO₂. It also carries nitrogen oxides.

Cells that carry hemoglobin in addition to red blood cells include A9 dopaminergic neurons, macrophages, alveolar cells, retinal pigment epithelium, hepatocytes, kidney mesangial cells and endometrial cells. In these cells, hemoglobin works as an antioxidant and regulates iron metabolism. Hemoglobinemia is a medical condition where an excess of hemoglobin is found in the blood plasma due to the effects of intravascular hemolysis.

What are the Similarities Between Ferritin and Hemoglobin?

• Ferritin and hemoglobin are two important metalloproteins.
• They are proteins made up of amino acids.
• Both are large globular proteins.
• These have subunits.
• Both are present in the blood.
• They are both connected to anemia.
• They have the function of carrying elements.

What is the Difference Between Ferritin and Hemoglobin?

Ferritin is an intracellular storage metalloprotein that stores the iron and releases it in a controlled manner, while haemoglobin is a transport metalloprotein in red blood cells that transports oxygen through the body. Thus, this is the key difference between ferritin and hemoglobin. Furthermore, ferritin has 24 subunits, while hemoglobin has 4 subunits.

The following infographic lists the differences between ferritin and hemoglobin in tabular form for side by side comparison.

Summary – Ferritin vs Hemoglobin

Metalloproteins are proteins that are bound by at least one metallic element such as iron, copper, cobalt, and manganese. Ferritin and hemoglobin are two important metalloproteins. Ferritin is an intracellular storage metalloprotein that stores the iron and releases it in a controlled manner, while haemoglobin is a transport metalloprotein in red blood cells that transports oxygen through the body. Thus, this summarizes the difference between ferritin and hemoglobin.

Reference:

1. “Ferritin Test.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 28 Nov. 2019.
2. “Low Hemoglobin: Causes & Symptoms.” Cleveland Clinic.

Image Courtesy:

1. “Ferritin 3foldchannel” By Acms116 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Haemoglobin representation” By Shriya Pai – Own work (CC BY-SA 4.0) via Commons Wikimedia