Earth Science: Chemistry – Organic and Biochemistry – Amino Acids
Hair and fingernails are external and visible structures made of proteins, which play an important role in almost all biological processes that take place in the human body.
As early as 1836, the Swedish chemist Jons Jacob Berzelius (1779-1848) coined the term proteins (from the Greek proteios, meaning “primary”). Proteins are the most important components of all living cells. They consist of individual building blocks, the amino acids, which are arranged in long chains. Amino acids, in turn, are carbonic acids, which have an amino group at the first carbon atom next to the carbonic acid.
Also located at the first carbon atom is a side chain that is specific for each amino acid. These side chains are straight, circular, or branched hydrocarbons. The human body requires 20 different amino acids, but the body itself can only produce some of these; the remainder will need to come from food, meaning a balanced diet is very important.
The composition of individual amino acids to proteins (protein biosynthesis) takes place along the ribosomes. The sequence of individual amino acids relative to each other is determined by the sequence of DNA. During protein biosynthesis, amino acids are linked via peptide bonds.
Structural features
These large proteins consist of many thousands of amino acids that are bonded to each other, as in a chain of pearls. Such a long chain forms spatial structures. The primary structure refers to the sequence of individual amino acids. Its side chains are distributed irregularly in space, or they are aligned in a regular pattern; this arrangement is the
secondary structure.
This includes a spiral, the ar-helix, and an almost parallel arrangement, the /3-sheet (also/J-pleated sheet), where certain segments of the chain run parallel to each other. Some proteins are rolled up like a ball of wool. In such an arrangement, it can happen that, for instance, the first amino acid of the chain (primary structure) is located in close proximity to an amino acid that is actually in position 800.
The spatial relationship of amino acids, which are in part within the primary structure but located far apart, is referred to as the tertiary structure. Hemoglobin is a protein in red blood cells, which transports oxygen. This protein consists of four individual proteins: the subunits. How these subunits are spatially oriented in relation to each other is, in turn, described by the quaternary structure.
In some subunits, proteins are linked by a covalent bond via two sulfur atoms that form a so-called disulfide bridge. Proteins take over various functions in the human body: they transport oxygen (hemoglobin) and other substances, they move muscles (myosin), serve as mechanical support (collagens), and attack foreign substances (antibodies). As hormones, proteins transmit signals, bond hormones (receptors), and accelerate reactions (enzymes).
BASICS
THE HUMAN BODY can produce only part of the amino acids it requires. Those that have to be taken in with food are referred to as “essential” (required for survival) amino acids.
“Conditionally essential” amino acids are amino acids that are sometimes essential: for example, for people with a specific disease or nutritional need.