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

What is the main purpose of haemoglobin in red blood cells?

1. To store nutrients

2. To combat infections

3. To transport oxygen

4. To support cell structure

The correct answer is: To transport oxygen

Haemoglobin plays a crucial role in the efficient transport of oxygen throughout the body. It is a protein found in red blood cells that binds to oxygen in the lungs, where oxygen concentration is high. Once haemoglobin picks up oxygen, it carries it through the bloodstream to various tissues and organs that need it for cellular respiration. This process is vital, as oxygen is necessary for the production of energy in cells. The ability of haemoglobin to release oxygen in response to lower concentrations of oxygen in the tissues further enhances its role as a transport molecule. The oxygenation and deoxygenation process that haemoglobin undergoes is also influenced by factors such as pH and carbon dioxide concentration, allowing for efficient oxygen delivery where it is most needed. In contrast, haemoglobin does not function to store nutrients, combat infections, or support cell structure. These functions are managed by other proteins and systems in the body. For example, antibodies combat infections, while structural proteins like collagen provide support to cells and tissues. Thus, the primary and most important function of haemoglobin is indeed to transport oxygen.