Chapter 22: Blood

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22.10:

Structure and Function of Erythrocytes

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Anatomy and Physiology

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Structure and Function of Erythrocytes

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22.9: Factors Affecting Erythropoiesis

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22.11: Hemoglobin

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There are 4.2 to 6 million erythrocytes, or red blood cells, per microliter of blood. These small cells are flattened biconcave discs with depressed centers. The erythrocyte plasma membrane is associated with proteins such as spectrin, forming a flexible cytoplasmic meshwork. This protein net enables erythrocytes to twist, turn, become cup-shaped, and regain their biconcave shape while passing through narrow capillaries. Additionally, erythrocytes can form stacks like dinner plates, allowing smooth passage through narrow capillaries without obstructing the blood flow. Mature erythrocytes lack nuclei and cell organelles, creating internal space for protein molecules. The available space is mainly occupied by oxygen-carrying hemoglobin molecules, constituting about 97% of the cytosolic proteins. Erythrocytes also lack mitochondria and generate their ATP by anaerobic processes. So, erythrocytes do not use the oxygen attached to hemoglobin, making them efficient oxygen carriers. Their flat and biconcave shape provides 30% more surface area relative to volume compared to other spherical cells. As a result, the cytoplasmic hemoglobin is close to the surface, facilitating swift exchange of gasses.

22.10:

Structure and Function of Erythrocytes

There are between 4.2 and 6 million erythrocytes, also known as red blood cells, in every microliter of blood. These cells are small, flattened biconcave discs with centers that are depressed.

The erythrocyte plasma membrane is associated with proteins such as spectrin, which forms a flexible cytoplasmic meshwork. This meshwork allows erythrocytes to twist, turn, become cup-shaped, and regain their biconcave shape as they pass through narrow capillaries. Additionally, erythrocytes can form stacks similar to dinner plates, enabling them to move smoothly through narrow capillaries without obstructing blood flow.

Mature erythrocytes lack nuclei and cell organelles, providing space for cell protein molecules. This space is primarily occupied by hemoglobin molecules, which carry oxygen and constitute about 97% of the cytosolic proteins.

Erythrocytes do not contain mitochondria and generate their ATP through anaerobic processes. As a result, they do not consume the oxygen bound to hemoglobin, making them highly efficient oxygen carriers.

Their flat and biconcave shape provides 30% more surface area relative to volume than spherical cells, positioning the cytoplasmic hemoglobin close to the surface to facilitate a swift exchange of gases.