What is the difference between active and passive transport? Which methods of crossing the membrane are considered active and which methods are considered passive?
The main difference between active and passive transport is that active transport requires energy input in the form of ATP, while passive transport does not require energy input.
In passive transport, substances move across the cell membrane from an area of higher concentration to an area of lower concentration, following the concentration gradient. This process includes simple diffusion, facilitated diffusion, and osmosis.
On the other hand, in active transport, substances move against the concentration gradient, from an area of lower concentration to an area of higher concentration. This requires the use of energy to pump the substances across the membrane. Active transport includes processes such as primary active transport (using ATP directly) and secondary active transport (using the energy from ion gradients created by primary active transport).
In summary, methods of crossing the membrane that are considered passive include simple diffusion, facilitated diffusion, and osmosis. Methods of crossing the membrane that are considered active include primary active transport and secondary active transport.