Adult human RBCs are enucleate. Which of the following statements are MOST APPROPRIATE explanation for this feature. The statement All their internal space is available for oxygen transport is WRONG Heamoglobin is the oxygen carrying molecule in the RBC. It comprises only about ONE-THIRD of the cell volume. The cell also produces various enzymes and substrates and also certain gas. Hence the option " All their internal space is available for oxygen transport" is NOT APPROPRIATE.