A Level Biology Practice Exam

Which factor primarily influences the affinity of haemoglobin for oxygen?

1. Temperature of the blood

2. pH levels in the blood

3. Carbon dioxide concentration

4. All of the above

The correct answer is: All of the above

Haemoglobin's affinity for oxygen is influenced by a combination of factors, which include temperature, pH levels, and carbon dioxide concentration. These elements are interrelated and part of what is known as the Bohr effect, which describes how increased levels of carbon dioxide and a decrease in pH (more acidic conditions) lead to a lower affinity of haemoglobin for oxygen. This process is crucial for facilitating the efficient release of oxygen to tissues that are metabolically active and producing more carbon dioxide. Additionally, temperature plays a significant role; as temperature increases, the affinity of haemoglobin for oxygen decreases. This means that in tissues that are generating heat through metabolic activity, haemoglobin will release oxygen more readily. Considering that each of these factors contributes to how haemoglobin binds and releases oxygen, the correct answer is that all these factors combined primarily influence the affinity of haemoglobin for oxygen. Understanding the interplay of these variables is essential for comprehending how our body regulates oxygen transport and delivery under varying physiological conditions.