And these protein complexes are responsible for creating those different types of processes and reactions. So, for instance, when we study DNA replication, we'll see that a single protein is not actually involved in DNA replication. We have many, many different types of proteins that have to work together and form these protein complexes to actually carry out the process of synthesizing, replicating DNA molecules and DNA strands. So another example is the transport proteins found inside our cell membrane. So cell membranes consist of phospholipids. And so these transport proteins have to actually interact with these phospholipids to be able to actually transport those molecules and ions across the cell membrane.