Select the one that supports the dissociation of oxyhaemoglobin in tissues .

Options

A. High `pO_2`
B. Low `pO_2`
C. Equal `pO_2`
D. Not dependent on `pO_2`

Answer

To determine which option supports the dissociation of oxyhemoglobin in tissues, we need to analyze the conditions that favor the release of oxygen from hemoglobin. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Understanding Oxyhemoglobin
- Oxyhemoglobin is formed when hemoglobin binds with oxygen molecules. Each hemoglobin molecule can bind up to four oxygen molecules.

### Step 2: Factors Affecting Oxyhemoglobin Dissociation
- The dissociation of oxyhemoglobin (the release of oxygen from hemoglobin) is influenced by several factors, including:
- Partial pressure of oxygen (PO2)
- Partial pressure of carbon dioxide (PCO2)
- Concentration of hydrogen ions (H+)
- Temperature

### Step 3: Conditions Favoring Dissociation
- High levels of PCO2, high levels of H+ ions (low pH), and high temperatures promote the dissociation of oxyhemoglobin. Conversely, low levels of PO2 promote the release of oxygen from hemoglobin.

### Step 4: Analyzing the Options
- A. High PO2: This condition would promote the formation of oxyhemoglobin, not dissociation.
- B. Low PO2: This condition would promote the dissociation of oxyhemoglobin, as tissues with low oxygen levels will encourage hemoglobin to release oxygen.
- C. Equal PO2: This condition would not favor dissociation or association.
- D. Not dependent on PO2: This statement is incorrect, as PO2 is a critical factor in the dissociation of oxyhemoglobin.

### Conclusion
- The option that supports the dissociation of oxyhemoglobin in tissues is **B. Low PO2**.