To What Does The Term “Ligand” Refer In Cell Biology?

A ligand is any chemical or atom that binds irreversibly to a protein in biology. A ligand may be a single atom or ion. It can also be a bigger, more complicated molecule composed of several atoms. A ligand may be a natural organic or inorganic molecule.

Additionally, ligands can be synthesized in the laboratory. It is because the essential qualities are included within its chemical structure. If this structure can be replicated in the laboratory, the synthetic ligand will interact similarly to a natural ligand.

How Does A Ligand Works In Biology?

To What Does The Term Ligand Refer In Cell Biology

The ligand moves through the watery fluids of an organism, including the blood, tissues, and cells themselves. The ligand moves at random, but it will ultimately contact a protein if the concentration is high enough.

Proteins that receive ligands might be receptors, channels, or perhaps the beginning of a complex chain of interconnected proteins.

When a ligand attaches to a protein, the protein experiences a conformational shift. It indicates that while no chemical connections have been made or broken, the physical action of the ligand fitting into the protein has altered the overall shape of the molecule.

It can initiate many activities. In most instances, the mobility of the protein itself activates another chemical route or causes the release of another messenger ligand to relay the message to other receptors.

The reversibility of the link between ligand and protein is essential to all forms of life. If ligands bonded irrevocably, they could not act as messengers, and most biological processes would collapse.

If ligands were altered in how an enzyme modifies a substrate, the ligand would become something different after the contact and could not be recycled as readily as a messenger. Because of their structure, biologically active proteins are active.

This shape interacts with the ligand to form a stable link between the two molecules, which will ultimately reverse, leaving both molecules unchanged. In a substrate-enzyme reaction, the substrate is irreversibly altered.

This capacity of the ligand to temporarily activate a protein and then be recycled enables the biological regulation of several interactions.

The amount of time a ligand remains bound to its receptor or particular protein depends on the affinity between the ligand and the protein.

If there is a strong affinity, the ligand will stick to the protein and alter its activity for a longer period. If the ligand has a poor affinity for the protein, it will be less likely to bind and leave the receptor more quickly.

Example Of A Ligand


Oxygen is a ligand that is frequently overlooked. Oxygen must reach all mitochondria in the body’s circulation and tissues for the organism to live. However, it is not simple to deliver oxygen everywhere.

If oxygen were allowed to permeate the tissue to the cells, it could only flow through a few cell layers.

Therefore, all creatures of a certain size must have a circulatory system. It isn’t easy to transport the oxygen ligand to the required location. Many species utilize specific proteins for this purpose.

Hemoglobin is the primary blood protein responsible for oxygen delivery in humans and other animals. The hemoglobin protein initially binds to a ligand termed heme, which contains an iron atom and can assist bind oxygen. Therefore, hemoglobin absorbs oxygen in the lungs.

As blood goes to the body, its carbon dioxide concentration increases. As a result, the pH decreases, and the structure of hemoglobin alters. It causes the release of the ligand, oxygen, which may then be absorbed by cells that require it.

Carbon monoxide is an important competitor of oxygen. It is because carbon monoxide has a greater affinity for hemoglobin than oxygen. In other words, once carbon monoxide is bonded to hemoglobin, it cannot be released.

It means that a person exposed to high levels of carbon monoxide will quickly have all of their hemoglobin saturated with the incorrect ligand.

Their body will be unable to transport oxygen to the brain and tissues. Even after receiving oxygen, the individual may still suffocate due to their incapacity to transfer oxygen.

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