What maintains the steep concentration gradients needed for successful gas exchange in the lungs? 1 Air flow in the alveoli is in the opposite direction to blood flow in the capillaries. 2 Blood arrives in the lungs with a lower oxygen concentration and a higher carbon dioxide concentration than the air in the alveoli. 3 Blood is constantly flowing through and out of the lungs, bringing a fresh supply of red blood cells.

Which statement helps to explain why there is no cartilage in the walls of the bronchioles?

Scientists have shown that the oxygen dissociation curves for haemoglobin of smaller mammals are to the right of thos…

What is an effect of an increased concentration of carbon dioxide in the blood?

Which statement is a correct comparison between saturated triglyceride molecules and unsaturated triglyceride molecul…

Which row correctly shows levels of protein structure that can be held together by each type of interaction?

Which statement describes an example of an extracellular enzyme?