Structure of proteins
Proteins consist of long, unbranched and complicatedly folded amino acid chains. Depending on how the amino acids are strung together and structured, completely different proteins with unique functions are formed. Small amino acid compounds are called peptides and proteins are referred to as having an amino acid chain length of over 100.
The chemical reactions that hold amino acids together are very complex but have been completely researched. It is known that there are forces of attraction between the individual amino acids and between several proteins. These are based on interactions between different chemical substances such as hydrogen (hydrogen bonds) and sulfur (disulfide bonds).
Electrical charges of the individual molecules can also have a magnetic effect, so to speak (Van der Waals forces, ion relationships, hydrophobic bonds).If the amino acids are arranged in the way the genetic material specifies, they follow a fixed sequence until a protein is formed. How the amino acids are arranged in sequence is called amino acid sequence or primary structure. This can be compared like pearls on a chain.
Next, they take on a spatial form, the secondary structure. The chain either winds like a spiral staircase (called alpha helix) or folds like strict chiffon fabric folds (beta fold). The next higher form of organization is the tertiary structure and describes the three-dimensional arrangement of the “spiral staircases” and “chiffon leaves” together.
These complex folds are created by which individual components have the same chemical property of being water-repellent. These then like to lie against each other. When several proteins join together to form a protein complex, this is called the quaternary structure.
However, such a protein complex is not rigid for the rest of its life: changes in the subunits result in changes in function. It can react with other substances in the body. A protein can have up to several thousand subunits, such as hemoglobin, which is located in the red blood cells and transports oxygen.
All articles in this series:
