Thanks to membrane barriers and transport proteins, the cell can accumulate nutrients in higher concentrations than exist in the environment and, conversely, dispose of waste products (Figure 3).

Like the exterior walls of a house, the plasma membrane is semi ... of carbon dioxide (Figure 3). The particular energy pathway that a cell employs depends in large part on whether that cell ...

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 ...