Hemoglobin assists transport of gases by a. combining with oxygen. b. combining with \(\mathrm{CO}_{2}\) c. combining with \(\mathrm{H}^{+}\) d. being present in red blood cells. e. All of these are correct.

Hemoglobin is a protein found in red blood cells that is responsible for transporting oxygen from the lungs to other parts of the body and carrying carbon dioxide back to the lungs for excretion. Additionally, hemoglobin also plays a role in maintaining the pH of blood.

Now, let's assess each statement provided in the exercise to determine whether or not they accurately describe hemoglobin's role in gas transport. a. Hemoglobin combines with oxygen: This statement is true. Hemoglobin binds to oxygen in the lungs, forming oxyhemoglobin, which is then transported throughout the body. b. Hemoglobin combines with \(\mathrm{CO}_{2}\): This statement is also true. Carbon dioxide is produced in the body as a waste product of cellular respiration, and hemoglobin transports it back to the lungs, where it can be expelled. Hemoglobin binds to carbon dioxide, forming carbaminohemoglobin. c. Hemoglobin combines with \(\mathrm{H}^{+}\): This statement is true. When there is an excess of \(\mathrm{H}^{+}\) ions, hemoglobin acts as a buffer, binding to the \(\mathrm{H}^{+}\) ions and preventing a decrease in blood pH. This is essential for maintaining the acidity of the blood within a narrow range that is compatible with the correct functioning of enzymes and metabolic processes. d. Hemoglobin is present in red blood cells: This statement is true. Hemoglobin is found in red blood cells, also known as erythrocytes. These cells make up roughly 40-45% of the blood's volume and are crucial for the transport of gases in the body. Given that all four statements (a, b, c, and d) are accurate descriptions of hemoglobin's role in gas transport, we can conclude that:

The correct answer is e. All of these statements are correct. Hemoglobin plays a crucial role in the transport of gases in the body, including binding to oxygen, carbon dioxide, and hydrogen ions and being present within red blood cells.