Above: Image © PhonlamaiPhoto, istockphoto.com

A cell’s nucleus serves as its control centre. You’d think that would mean a cell is nothing without its nucleus. But interestingly, some of your cells don’t even have a nucleus. This includes one of your most important types of cells: your red blood cells (RBCs), also called erythrocytes.

RBCs are always at work, exchanging oxygen and carbon dioxide with the cells that form your tissues and organs. Thanks to this gas exchange, your body works as it should. But wait - how can RBCs do such important work without a control centre?

Here’s the interesting thing: not having nuclei actually makes them better at their job! They have more space and a more efficient shape to work with.

Did you know? RBCs start out with a nucleus. They lose it during the final stage of erythropoiesis, the process by which they mature.

No nucleus, more space

Do you use a backpack to carry your books to school? If so, imagine that you put a big basketball in it. You wouldn’t be able to fit as many books in your backpack, and it would be bigger and rounder because of the basketball taking up all that space. But if you were to take that basketball out, the bag would get smaller and you’d have more space to carry books.

Your backpack does a better job of carrying your books without the basketball inside it. Similarly, your RBCs do a better job of carrying necessities without the nuclei inside. The cell’s cytoplasm becomes more spacious, allowing the RBC to have more hemoglobin molecules. That’s important because hemoglobin carries the oxygen molecules in the blood. An RBC with more hemoglobin can transport more oxygen.

Did you know? A healthy red blood cell has approximately 250 million molecules of hemoglobin!

No nucleus, better shape

That extra cytoplasm space has another advantage, too. It makes it easier for the cells to adopt a biconcave disk shape, where the top and bottom surfaces of the RBC indent inwards like a bowl.

It’s important for the RBC to have this shape, but scientists haven’t yet agreed why. Some scientists believe that the biconcave shape lets the RBC exchange oxygen and carbon dioxide much more quickly. That’s because this shape increases the surface area of an RBC, providing more surfaces where gas exchange can happen. Other scientists believe the biconcave shape allows the RBC to flow through blood vessels more easily.

Did you know? Mammals are the only group of animals with red blood cells that have no nucleus. Fish, reptiles and birds have red blood cells with nuclei.

No nucleus, better workouts

Now let’s put that basketball to use. If your red blood cells had nuclei, do you think you’d be able to play basketball as well? Probably not.

After all, if your cells couldn’t carry as much oxygen, your muscles wouldn’t function at their best. You’d be weaker, and your muscles would tire much faster. In basketball, this lower amount of oxygen would make it much harder for you to shoot and rebound the ball. You’d even have a harder time running up and down the court.

In fact, you’d have a hard time doing anything that took a lot of physical effort. Aren’t you glad your red blood cells lost their nuclei?

Learn more

Shape and Biomechanical Characteristics of Human Red Blood Cells in Health and Disease (2010)
M. Diez-Silva, M. Dao, J. Han, C.-T. Lim & S. Suresh, MRS Bulletin 35

How Red Blood Cells Nuke Their Nuclei (2008)
C. Carr, Whitehead Institute

Red blood cell
The Editors of Encyclopædia Britannica, Encyclopædia Britannica

Tushar Sharma

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