Concerted vs Sequential Model

Notes:

The concerted model of allostery is a theory that states a protein is initially either in the T-state or R-state. The binding of a substrate just shifts this. For example, the enzyme is in the T-state until bound, then all subunits move to the R state. Translating this to hemoglobin, this model suggests that once the first O2 binds, all of the other subunits transition to the R state and make O2 binding at those sites easier. 

The sequential model is a theory that a protein contains subunits that are all in the T-state until a molecule binds to one. This results in a conformational change that affects the closest subunits and causes them to become something between the T and R state where they are a bit more likely to bind. This continues as more molecules bind, each gaining more and more affinity for the substrate. This is exemplified through the squares missing corners!