Hemoglobin

Inside your red blood cells is something special.

It is a part of your blood that uses iron. This part helps carry air to your body.

It takes air from your lungs. Then it moves that air to your muscles. This helps your body stay strong. Most animals have this in their blood. Even some plants have a version of it! It is a very busy helper in your body.

Inside your red blood cells is a special protein. We call this hemoglobin.

It contains iron to help move oxygen through your body.

Hemoglobin works like a tiny delivery truck. It picks up oxygen from your lungs or gills. Then, it carries that oxygen to your tissues. This oxygen gives your body the power to work.

One hemoglobin molecule can carry up to four oxygen molecules at once. It also moves other gases, like carbon dioxide. This helps your body get rid of waste.

Most animals have hemoglobin. Even some plants have a version of it!

In some cold places, certain fish have lost their hemoglobin. This is a way they adapt to the ice. Other animals, like mice and birds, have special hemoglobin. It helps them live in thin air high up in the mountains.

Scientists like Max Perutz studied how hemoglobin is shaped.

He won a Nobel Prize for his work. He showed how the tiny parts fit together to do their job.

Hemoglobin is a special protein that helps living things breathe. It is found inside red blood cells and contains iron. This protein is very important because it carries oxygen through the body.

Almost all animals with backbones have it. The only exception is a family of fish called Channichthyidae. Hemoglobin picks up oxygen from lungs or gills. It then carries that oxygen to other tissues. This allows animals to use oxygen for their metabolism.

How does this tiny protein work? A single hemoglobin molecule can bind to four oxygen molecules at once. It acts like a delivery system for gases. It carries oxygen to where it is needed. It also carries away some carbon dioxide from the body. This gas is called carbaminohemoglobin when it binds to the protein.

It even carries a molecule called nitric oxide. This helps the body regulate itself. Hemoglobin makes blood much better at carrying oxygen than plasma alone.

Many people have studied this protein over a long time. In 1825, Johann Friedrich Engelhart found something amazing. He saw that the ratio of iron to protein was the same in many species. He even calculated the mass of the protein for the first time. Later, in 1959, Max Perutz found the exact molecular structure.

He won a Nobel Prize in 1962 for this great work. His work helped us see how the protein is built. This was a huge step for science.

There are many interesting facts about hemoglobin numbers. A healthy human has 12 to 20 grams of it in every 100mL of blood. In mammals, it makes up about 96% of a red blood cell's dry weight.

Different genes make the different parts of the protein. In humans, the HBA1, HBA2, and HBB genes are responsible. Some changes in these genes can cause diseases like sickle-cell disease. These are called hemoglobinopathies. They can lead to a condition called anemia.

Hemoglobin is also a great example of how life adapts. Some animals have special versions to live in tough places. For example, Andean hummingbirds have hemoglobin that works in thin air.

High-altitude mice also have genes that help them use oxygen better. Even plants have a version called leghemoglobin. It protects certain plants from oxygen poisoning. This shows how important this protein is for life on Earth.

Hemoglobin is a vital protein that facilitates the transportation of oxygen throughout the bodies of most living things. It is a metalloprotein, meaning it contains metal, and a chromoprotein, which means it has color. This protein is found inside red blood cells and is essential for aerobic respiration. Aerobic respiration is the process that powers an animal's metabolism. Without hemoglobin, most vertebrates could not move oxygen from their respiratory organs, such as lungs or gills, to their tissues.

Almost all vertebrates contain this protein, with the single exception of the fish family Channichthyidae.

The structure of a hemoglobin molecule is quite complex. It is composed of subunits called globin molecules, which are polypeptides. Polypeptides are long, folded chains of specific amino acids. Each globin subunit contains an embedded heme group. A heme group is a structure that contains one iron atom. This iron atom can bind to one oxygen molecule through ion-induced dipole forces. In the most common type of mammalian hemoglobin, there are four such subunits working together.

This four-part structure allows the molecule to bind and transport up to four oxygen molecules at once.

Beyond just oxygen, hemoglobin acts as a multi-purpose carrier for other gases. It carries about 20% to 25% of the body's respiratory carbon dioxide. When carbon dioxide binds to the heme protein, it forms a substance called carbaminohemoglobin. The molecule also transports nitric oxide, which is an important regulatory molecule. It carries nitric oxide by binding it to a thiol group within the globin protein. This allows the molecule to release nitric oxide at the same time it releases oxygen.

Scientists have spent centuries uncovering the secrets of this molecule. In 1825, Johann Friedrich Engelhart discovered that the ratio of iron to protein was identical across several different species. He used the atomic mass of iron to calculate the molecular mass of hemoglobin. This was the first time anyone had determined the mass of a protein. While some colleagues ridiculed his "hasty conclusion," Gilbert Smithson Adair confirmed his results in 1925. Later, in 1959, Max Perutz determined the actual molecular structure of hemoglobin using X-ray crystallography.

Perutz shared the 1962 Nobel Prize in Chemistry for this discovery.

The numbers associated with hemoglobin show how much it impacts our biology. A healthy human has between 12 and 20 grams of hemoglobin in every 100mL of blood. In mammals, hemoglobin makes up about 96% of a red blood cell's dry weight. It also accounts for about 35% of the total weight of the cell when water is included. The oxygen-binding capacity of hemoglobin is 1.34mL of O2 per gram. This capacity increases the total oxygen capacity of blood seventy-fold compared to what plasma could carry alone.

Genetics play a massive role in how hemoglobin is built. The amino acid sequence of the globin chains is translated from segments of DNA called genes. In humans, hemoglobin A is the main form found in adults. It is coded by three specific genes: HBA1, HBA2, and HBB. The HBA1 and HBA2 genes are located on chromosome 16, while the HBB gene is on chromosome 11. Mutations in these genes can lead to hemoglobinopathies. These are hereditary diseases like sickle-cell disease or thalassemias, which often result in anemia.

Evolution has shaped hemoglobin to help animals survive in extreme environments. For example, Andean hummingbirds have mutations that allow them to thrive in thin air at high altitudes. Their hemoglobin has a lower affinity for inositol hexaphosphate, which helps them bind oxygen more easily in low-pressure environments. Similarly, deer mice have genetic differences that allow highland populations to use oxygen more efficiently. Even plants use a related version called leghemoglobin. This version helps protect anaerobic systems from oxygen poisoning.