CBSE Class 10 Answered

The RBCs have nuclei during early phases of their formation, but extrude them during development as they mature in order to provide more space for hemoglobin. In mammals, erythrocytes also lose all other cellular organelles such as their mitochondria, golgi apparatus and endoplasmic reticulum. As a result of not containing mitochondria, these cells use none of the oxygen they transport; instead they produce the energy carrier ATP by lactic acid fermentation of glucose. Because of the lack of nuclei and organelles, mature red blood cells do not contain DNA and cannot synthesize any RNA, and consequently cannot divide and have limited repair capabilities.

After maturation, these cells live in blood circulation for about 100 to 120 days. This short lifespan is due to lack of nucleus and other cell organelles.