If the membrane is highly permeable to solute as well as to water, no water flow will occur and, therefore, the externally applied pressure required to stop osmosis is zero.
Subsequently, question is, does filtration require energy? Filtration is the movement of water and solute molecules down the concentration gradient, e.g. in the kidneys, and osmosis is the diffusion of water molecules across a selectively permeable membrane. None of these processes require energy.
Furthermore, why does diffusion not require any energy?
It occurs down a concentration gradient - molecules move from an area of high to lower concentration. This does not require a supply of energy because diffusion is a spontaneous process.
Is Pinocytosis active or passive?
Pinocytosis is the act of grabbing some liquid. The whole cell works during the process. It is not just some membrane proteins taking in a couple of molecules as in active transport. Phagocytosis is a cell taking in a large object that it will eventually digest.
