OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is a major characteristic of red blood cells?

1. They have a nucleus

2. They are flexible and biconcave

3. They store glucose

4. They are the largest blood cells

The correct answer is: They are flexible and biconcave

Red blood cells, also known as erythrocytes, exhibit a distinctive biconcave shape that enhances their ability to transport oxygen efficiently throughout the body. This unique structure increases the surface area to volume ratio, allowing for optimal gas exchange. The flexibility of red blood cells enables them to squeeze through the narrowest capillaries without rupturing, ensuring that they can reach all tissues of the body effectively. In contrast, red blood cells do not contain a nucleus, which allows for more space to accommodate the protein hemoglobin that binds to oxygen. They also do not play a role in glucose storage, as glucose is primarily stored in the liver as glycogen. Furthermore, red blood cells are not the largest blood cells; that title belongs to white blood cells. Thus, their biconcave shape and flexibility stand out as key characteristics that facilitate their primary function of oxygen transport.