What would have happend ? If.........
RBCs had mitochondria.
RBC's are a type of cells which are found in blood. Their function is to carry oxygen to different cells and tissues of the body. They do not contain mitochondria for two purposes:
firstly, it saves the space in the red blood cells and so more of oxygen can bind to it
secondly, it prevents the use of oxygen which is bounded to RBC's.
If mitochondria would have been present in RBC's, the oxygen which is carried by them will be used up by the RBC's. Thus, there will be less or no oxygen left which can be transported to the cells and tissues.