In the gills of a fish, water flows over the lamellae in the opposite direction to the flow of blood inside them. How does this increase the rate at which oxygen diffuses into the blood?
It increases the surface area of the lamellae that is in contact with the water.
It keeps a concentration gradient for oxygen along the whole length of a lamella.
It reduces the thickness of a lamella wall, so oxygen has a shorter path to travel.
It increases the temperature of the blood, so the oxygen particles move more quickly.
58 exam-style questions on AQA GCSE Biology 1.3 Transport in cells, covering 1.3.1 Diffusion, 1.3.2 Osmosis, and 1.3.3 Active transport. Each one has a worked solution and a mark scheme showing where the marks go.