Oxygen dissociation curve of haemoglobin is

Options

A. sigmoid
B. hyperbolic
C. hypobolic
D. hypobloic

Answer

### Step-by-Step Solution:

1. **Understanding the Oxygen Dissociation Curve**: The oxygen dissociation curve of hemoglobin, also known as the oxyhemoglobin dissociation curve, is a graphical representation that shows how hemoglobin binds to oxygen at different partial pressures of oxygen (pO2).

2. **Axes of the Curve**: The curve is plotted with the proportion of hemoglobin that is saturated with oxygen on the vertical axis (y-axis) and the partial pressure of oxygen (pO2) on the horizontal axis (x-axis).

3. **Shape of the Curve**: The oxygen dissociation curve is characterized by a sigmoidal (S-shaped) curve. This shape indicates that hemoglobin's affinity for oxygen increases as more oxygen molecules bind to it.

4. **Significance of the Sigmoidal Shape**: The sigmoidal shape of the curve reflects cooperative binding, meaning that the binding of one oxygen molecule to hemoglobin increases the likelihood of additional oxygen molecules binding. This is crucial for efficient oxygen uptake in the lungs and release in the tissues.

5. **Conclusion**: Based on the understanding of the oxygen dissociation curve and its characteristics, the correct answer to the question is that the oxygen dissociation curve of hemoglobin is **sigmoid**.

### Final Answer:
The oxygen dissociation curve of hemoglobin is **sigmoid**.

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