Which of the following substances are transported by hemoglobin in erythrocytes?

• A. Glucose
• B. Cholesterol
• C. Amino acids
• D. Oxygen

Answer: (D)

Verified step by step guidance

1. Understand the role of hemoglobin: Hemoglobin is a protein found in erythrocytes (red blood cells) that primarily functions to transport oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs.
2. Identify the substances hemoglobin can transport: Hemoglobin is specifically designed to bind and transport gases like oxygen (O₂) and carbon dioxide (CO₂) due to its structure and affinity for these molecules.
3. Evaluate the options given: Glucose, cholesterol, and amino acids are not transported by hemoglobin. These substances are typically transported in the blood plasma or through other mechanisms such as lipoproteins for cholesterol.
4. Focus on oxygen transport: Hemoglobin binds oxygen in the lungs where the oxygen concentration is high, forming oxyhemoglobin. It then releases oxygen in the tissues where the concentration is lower, facilitating cellular respiration.
5. Conclude with the correct answer: Based on the function of hemoglobin, the correct answer is oxygen, as it is the primary substance transported by hemoglobin in erythrocytes.