The pectoralis major muscle can be divided into groups of fibers superior, or and inferior, or

The pectoralis major muscle can be divided into groups of fibers superior, or claviclular, and inferior, or sternocostal.

Pectoralis is a major muscle fundamentally responsible for shoulder joint movements.  It is divided into four actions and two groups of fibers, anatomically the superior side and interior side.  These movements are often used in everyday lives like throwing and flapping the arms.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products