A substance makes capillary walls thicker without changing the concentration difference between blood and surrounding cells. What is the most likely effect on oxygen transfer?
It increases because the exchange surface becomes wider.
It increases because oxygen travels a shorter distance.
It decreases because the oxygen concentration difference disappears.
It decreases because oxygen travels a longer distance.
42 exam-style questions on Edexcel GCSE Biology 8.2 Blood and circulation, covering 8.2.1 Structure and function of the blood, 8.2.2 Structure of blood vessels, 8.2.3 Structure of the heart and circulatory system, and 8.2.4 Cardiac output. Each one has a worked solution and a mark scheme showing where the marks go.