Substances get in and out of cells through Diffusion, Osmosis and Active Transport.
Diffusion and Osmosis involve substances moving from an area of high concentration, to low concentration. BUT, a cell may need to take a substance AGAINST a concentration gradient- this is called ACTIVE TRANSPORT.
Active transport uses energy from respiration to carry substances over a cell membrane using a protein.
Active transport is found in:
-Glucose moving from kidney to blood
- Mineral Ions in soil moving into plants.
EXCHANGE OF GASES IN THE LUNGS
The lungs exchange oxygen (needed for AEROBIC respiration), and carbon dioxide (a product of respiration).
Oxygen + Glucose > Carbon Dioxide + Water + Energy
The lungs have millions of tiny air sacs named ALVEOLI, which increase the surface area of the lungs greatly.
They also have a rich blood supply, a steep concentration gradient with movement of gases, they are moist to aid diffusion, and the cells around the alveoli are very thin, so gases do not have to travel far.