Introduction to Biology

The alveoli are the tiny air sacs within the lungs where the exchange of gases takes place. They are the final branching of the respiratory tree and act as the primary site for the exchange of oxygen and carbon dioxide between the lungs and the bloodstream. To answer the question of which substance is not transferred by the alveoli, we must first understand what is typically exchanged during the respiratory process. The primary function of the alveoli involves the transfer of: 1. **Oxygen (O_2)**: Oxygen is inhaled into the lungs and diffuses through the walls of the alveoli into the capillaries, where it binds to hemoglobin in red blood cells and is transported to the tissues of the body. 2. **Carbon Dioxide (CO_2)**: Carbon dioxide is a waste product of cellular metabolism and is transported in the blood back to the lungs, where it diffuses from the capillaries into the alveoli to be exhaled. Given these two primary gases exchanged in the alveoli, we can consider other substances that might be mentioned in a list: - Nitrogen (N_2): Although nitrogen is the most abundant gas in the atmosphere, it is not significantly transferred across the alveolar membrane because it is not very soluble in blood and is not involved in the process of cellular respiration. - Water vapor (H_2O): Some water vapor is normally exhaled with the carbon dioxide, but the primary purpose of the alveoli is not to transfer water vapor. - Nutrients (e.g., glucose, amino acids): Nutrients are not gases and are not exchanged in the alveoli. They are absorbed through the digestive system and transported to cells via the bloodstream. - Blood cells: Blood cells, including red and white blood cells, do not pass through the alveolar wall. They are contained within the blood vessels and are involved in transporting gases and immune responses, respectively. Based on the above information, the substance that is not transferred by the alveoli in the human respiratory system is likely to be nutrients or blood cells, as these are not involved in the gaseous exchange process. If the question provided a list of options, the correct answer would be the one that is not a gas typically involved in respiration, such as nutrients or blood cells.

Question

Which of the following is not transferred by alveoli in the human respiratory system?

Solution

PrepMate

Ask a tutor

If you have any additional questions, you can ask one of our experts.