For instance, let's take hemoglobin. It generally has 146 amino acids, but not all them are essential for the protein to be functional. So, if we a ask a question as to how many different amino acids are necessary for the protein to be known as the  hemoglobin  protein, then the answer depends on many things. Whenever changes in amino acid affects the physical structure of protein molecule, the affected protein becomes inactive.
A reference point in physics is a point in space, regardless of the  type of geometry that you are using, that stays still and does not  move. From this point, the behavior â¦ of an object moving through  that space can be determined.
Freebase(4.54 / 22 votes)Rate this definition: Reference is a relation between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to refer to the second object. The second object â the one to which the first object refers â is called the referent of the first object. The term reference is used in many spheres of human knowledge, adopting shades of meaning particular to the contexts in which it is used.