Internal respiration (cellular) is?

Internal respiration (cellular) is?

• A. Oxygen diffuses into carbon dioxide and diffuses out
• B. Carbon dioxide diffuses from tissues into blood
• C. Oxygen diffuses into blood from tissues
• D. Oxygen diffuses into tissues; Carbon dioxide diffuses from tissues into blood

Answer: (D)

Internal respiration is the diffusion of gases between the blood in systemic capillaries and body tissues. Oxygen moves from blood into tissues because arterial blood arriving at tissues has a high partial pressure of O2 while metabolically active tissues use up O2, creating a lower tissue PO2. Carbon dioxide, a waste product of cellular metabolism, accumulates in tissues and diffuses into the blood where its partial pressure is lower, so it can be carried back to the lungs. Therefore the best description is that oxygen diffuses into tissues and carbon dioxide diffuses from tissues into blood.

Internal respiration is the diffusion of gases between the blood in systemic capillaries and body tissues. Oxygen moves from blood into tissues because arterial blood arriving at tissues has a high partial pressure of O2 while metabolically active tissues use up O2, creating a lower tissue PO2. Carbon dioxide, a waste product of cellular metabolism, accumulates in tissues and diffuses into the blood where its partial pressure is lower, so it can be carried back to the lungs. Therefore the best description is that oxygen diffuses into tissues and carbon dioxide diffuses from tissues into blood.