Intermediate Topic 703 of 1102 Inorganic Chemistry
Hemoglobin
An iron-containing protein transporting oxygen in blood.
In-depth explanation of Hemoglobin
Haemoglobin is a tetrameric protein in red blood cells, made of four globin chains that each contain a haem group with an Fe2+ ion held in a porphyrin ring. Oxygen binds reversibly to the iron, which is low spin when oxygenated and high spin when deoxygenated. The four subunits cooperate, so the oxygen binding curve is sigmoidal, which allows efficient loading in the lungs and release in the tissues. Carbon monoxide binds the haem iron about 200 times more strongly than O2, blocking oxygen transport. Cyanide also binds the iron and is highly toxic.
Going deeper: Hemoglobin
Key ideas: Tetramer of four globin chains, each with heme where Fe2+ binds O2 reversibly in a porphyrin ring. Cooperative binding gives a sigmoidal curve with Hill coefficient near 2.8; the oxygenated state is low spin and pulls Fe into the ring plane, moving helices and raising affinity of other sites. The Bohr effect: lower pH and high CO2 release O2 in tissue. CO binds about 200 times tighter than O2; oxidation to Fe3+ gives methemoglobin which cannot carry O2.
Common mistakes and connections: Students think iron is oxidized when binding O2; it stays Fe(II) formally, oxygenation not oxidation. Myoglobin has a hyperbolic curve and higher affinity, storing O2. Sickle cell anemia arises from a single amino acid change (Glu to Val). Links to equilibrium, cooperative binding, crystal field spin states and CO toxicity.
Visualization of Hemoglobin
Octahedral d-orbital splitting of the iron centre in haem: the energy gap between t2g and eg changes with the bound ligand and sets its spin state. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Healthy arterial blood is about 97 percent saturated with oxygen, so most of its haemoglobin carries O2.
Frequently asked questions about Hemoglobin
What is Hemoglobin?
An iron-containing protein transporting oxygen in blood.
Is Hemoglobin a beginner, intermediate or advanced topic?
Hemoglobin is a intermediate topic in Inorganic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Hemoglobin?
Study these earlier topics in Inorganic Chemistry first: Zeigler-Natta Catalysts, Wilkinson's Catalyst, Bioinorganic Chemistry.
What comes after Hemoglobin?
The next topics in Inorganic Chemistry are Chlorophyll and Cisplatin.
Can I practise Hemoglobin with quizzes?
Yes. The interactive lesson includes a self-check question on Hemoglobin, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Hemoglobin fits in Inorganic Chemistry
Hemoglobin is topic 88 of 113 in Inorganic Chemistry.