Serine is a polar amino acid with an alcohol-OH function.
This hydroxyl group allows serine to be phosphorylated. It is also possible for this amino acid to be involved in a bond with an oligosaccharide (also commonly called «sugar»)
The bond between the amino acid and this «sugar» involves the oxygen of the -OH function: we then speak of an O-osidic bond. The protein with carbohydrate bonds is called glycoprotein.
Serine is present in mucin, the glycoprotein of mucus, preventing the mucin from being broken down.
The mucus then carries out its various functions: it humidifies the air inhaled, warms it, captures the various particles present (bacteria, viruses, dust), thus preventing them from entering our body. Mucus contains antibodies, enzymes and proteins whose presence ensures the defence of our body.
Serine is present in many proteins. It is also the most abundant amino acid
Serine is an amino acid that makes up mucus. Thus, the latter can ensure its functions of protection, barrier and defence against bacteria and viruses.