This takes place when molecules diffuse across the cell membrane by travelling through specific transport proteins. It occurs down a concentration gradient - molecules move from an area of high to ...

The oxygen diffuses across the partially permeable membrane of the alveoli cells and the capillary wall, into the red blood cells to be carried around the body. Osmosis close osmosisThe movement ...

MERS-CoV and Respiratory Syncytial virus to find all the keys and passwords that give viruses access to the interior of our cells and that allow transport across tissues.