Which is true?

Options

A. `H^(+)` ions released from carbonic acid combine with haemoglobin to form haemoglobinic acid
B. oxyhaemoglobin of erythrocytes is alkaline
C. more than 70% of carbon diodxide is trnsferred form tissue to lungs as carbamino compounds
D. in healthy person haemglobin cont ent is more thant `25g / 100` ml

Answer

To determine which statement is true among the given options, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Analyze the First Statement:**
- The statement claims that hydrogen ions released from carbonic acid combine with hemoglobin to form hemoglobinic acid.
- **Explanation:** Carbonic acid (H2CO3) dissociates into bicarbonate (HCO3-) and hydrogen ions (H+). The H+ ions can bind to hemoglobin, forming hemoglobinic acid (HbH). This statement is **correct**.

2. **Analyze the Second Statement:**
- The statement claims that oxyhemoglobin of erythrocytes is alkaline.
- **Explanation:** Oxyhemoglobin (HbO2) is formed when oxygen binds to hemoglobin. It is known to be **acidic** in nature, not alkaline. Therefore, this statement is **incorrect**.

3. **Analyze the Third Statement:**
- The statement claims that more than 70% of carbon dioxide is transferred from tissue to lungs as carbamino compounds.
- **Explanation:** While carbon dioxide does form carbamino compounds with hemoglobin, only about **30%** of carbon dioxide is transported this way. The majority (over 70%) is transported as bicarbonate ions (HCO3-). Thus, this statement is **incorrect**.

4. **Analyze the Fourth Statement:**
- The statement claims that in a healthy person, hemoglobin content is more than 25 grams per 100 ml.
- **Explanation:** In healthy individuals, hemoglobin levels typically range from **12 to 20 grams per 100 ml** of blood. Therefore, this statement is also **incorrect**.

### Conclusion:
- The only correct statement among the options provided is the **first statement** about hydrogen ions combining with hemoglobin to form hemoglobinic acid.

### Final Answer:
- **The true statement is:** Hydrogen ions released from carbonic acid combine with hemoglobin to form hemoglobinic acid.

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