serine

This is not a word you hear every day, but it names something your body uses all the time. It is an amino acid, one of the small units that join together to make proteins. You can think of proteins as long chains built from many different pieces, and this is one of them.

It was first found in silk, which is how it got its name. Scientists study it because it helps with many basic processes in living cells. You probably will not use this word in daily conversation unless you are talking about biology, chemistry, or nutrition, but it refers to a basic part of life.

Serine is an amino acid, one of the small chemical units that living things use to build proteins. Amino acids join together in long chains, and those chains fold into proteins that do much of the work inside cells. Proteins help form body tissues, carry materials, and support chemical reactions that keep organisms alive.

The word comes from the Latin word sericum, meaning "silk," because this amino acid was first isolated from silk. That bit of history is useful because it explains why the name sounds unusual and why silk is often mentioned when people define it.

In biochemistry, serine is often written as *Ser or S*. It is a polar amino acid, which means it mixes well with water and often appears in parts of proteins that interact with watery environments inside or outside the cell. It also plays an important part in enzyme activity and cell signaling, so it matters not just as a building block but also as an active part of how cells work.

Your body can make serine on its own, so it is called a non-essential amino acid in nutrition. Even so, it is still essential in the everyday sense: cells need it to function properly. You may never use the word in casual conversation, but in biology it refers to a common and important amino acid found throughout living systems.