Video Transcript
Red blood cells do not contain a
nucleus. What is the advantage of this? (A) There is more space within the
cell for the genetic material. (B) The cell can form a convex
shape to increase its surface area. (C) The cell can divide more
rapidly to make new cells. (D) There is more space within the
cell for hemoglobin. (E) There is more space within the
cell for mitochondria.
Why don’t red blood cells contain a
nucleus? To understand why this is, we must
understand the function of red blood cells and the way they work. Let’s first recap the anatomy of a
red blood cell. This will help us eliminate some of
the answers.
First, a red blood cell has a
distinct shape, a disc with two concavities on the top and bottom. So we can eliminate answer (B),
“The cell can form a convex shape to increase its surface area,” because we know
that red blood cells have a concave shape, not convex.
In addition, red blood cells are
highly specialized, meaning they are very different from other cells in the
body. One difference is that they do not
have organelles or nuclei. Another difference is that mature
red blood cells do not contain DNA or RNA and are therefore unable to replicate. Knowing this, we can eliminate
answer (A), “There is more space in the cell for genetic material,” because red
blood cells do not contain genetic material.
We can also eliminate answer (C),
“The cell can divide more rapidly to make new cells,” because without genetic
material they are unable to divide. Finally, we can eliminate answer
(E), “There is more space within the cell for mitochondria,” because we know that
red blood cells do not have organelles, including mitochondria.
By process of elimination, there is
only one answer left, which must be the correct one. To explain this answer, we need to
understand the main function of red blood cells and how they work.
Red blood cells transport oxygen to
respiring tissues and organs. They do this by binding the oxygen
breathed in by the lungs and then releasing oxygen to the tissues of the body. The molecule that oxygen binds to
is called hemoglobin. Each hemoglobin molecule can bind
up to four oxygen molecules. Because the primary function of red
blood cells is to transport oxygen, it is an advantage to have the maximum possible
number of hemoglobin molecules in each red blood cell.
Therefore, it makes sense that red
blood cells do not contain nuclei so that there is more space within the cell for
hemoglobin. The correct answer is (D). There is more space within the cell
for hemoglobin.
