Figure 5: Representation of a tight junction in the BBB
Proteins are a group of highly diverse molecules. When comparing our cells to small factories, proteins would constitute all the components and tools such as as the machines, tubes and manual workers that altogether make the cell perform their necessary function.
Proteins, like Lego constructions, are build up from different smaller units called amino acids. The primary structure of proteins is determined by the number and order of these building blocks. Using chemical interactions between the amino acids within the same chain or other chains, proteins can form unique structures enabling them to specifically fulfil their biological functions. These functions are as diverse as the proteins themselves ranging from simple features like tubes that make the structures of our cells, up to the highly complex and specialized functions of enzymes, hormones, antibodies and many more.