It's not the presence of protein that determines blood type, but rather the specific structure of carbohydrate molecules attached to proteins and lipids on the surface of red blood cells. These carbohydrates act as antigens, which trigger an immune response if they are foreign to the body.

Here's a breakdown:

* ABO blood group system: This system is based on the presence or absence of two antigens, A and B, on the surface of red blood cells.

* Type A blood has the A antigen.

* Type B blood has the B antigen.

* Type AB blood has both A and B antigens.

* Type O blood has neither A nor B antigens.

* Rh blood group system: This system focuses on the presence or absence of the RhD antigen.

* Rh-positive blood has the RhD antigen.

* Rh-negative blood lacks the RhD antigen.

The role of proteins:

While proteins are involved in the structure of the red blood cell membrane, they are not directly responsible for the specific antigens that determine blood type. The carbohydrates attached to these proteins are the key factors.

To summarize:

It's not the protein itself but the specific carbohydrates attached to proteins and lipids on the surface of red blood cells that determine blood type. These carbohydrate structures act as antigens, triggering immune responses if they are foreign to the body.