Question 15

Red blood cells lack a nucleus.

Red blood cells, also known as erythrocytes, are unique among human cells in that they do not contain a nucleus. This adaptation allows them to carry more hemoglobin and, consequently, more oxygen throughout the body.

A) platelet

Platelets are small cell fragments involved in blood clotting, and while they do not have a nucleus, they are not classified as complete cells. They derive from megakaryocytes and are crucial to hemostasis, but they are not the answer to this question regarding cell types lacking a nucleus.

B) red blood cell

Red blood cells are indeed the correct answer, as they are the only cell type listed that completely lacks a nucleus. During their maturation in the bone marrow, they expel their nucleus to maximize space for hemoglobin, which is essential for their primary function of oxygen transport.

C) white blood cell

White blood cells, or leukocytes, are vital components of the immune system and contain a nucleus. They play roles in defense against pathogens and are classified into several types, all of which retain their nucleus, making this option incorrect.

D) phagocyte

Phagocytes are a subset of white blood cells that engulf and digest pathogens and debris. They possess a nucleus and are essential for the immune response. Therefore, this option does not meet the criteria of lacking a nucleus.

Conclusion

Red blood cells are the only cell type listed that entirely lacks a nucleus, which is a significant adaptation for their function in oxygen transport. In contrast, platelets, white blood cells, and phagocytes all possess a nucleus, making them incorrect choices for this question. Thus, option B is definitively the right answer.