Question #7a1a6
1 Answer
Movement of particles such as water or solutes without the input of ATP across a plasma membrane.
Explanation:
Passive transport is the movement of particles without the input of ATP (note: passive transport is not movement without energy). Passive transport will occur across a plasma membrane if the particle is able to pass through the plasma membrane with or without assistance from plasma proteins, but no ATP is required.
Passive transport can be observed if there is a concentration gradient created across a membrane. For example with water, if one side has a greater water potential than the other, water will move by osmosis (a form of passive transport for water) from the area/side of high water potential to the area/side of lower water potential. This occurs until equilibrium is achieved and there is no more net movement of water (note: the water does not stop moving across the membrane, the movement of both sides are the same, thus there is no observable change).
Passive transport can also occur with the assistance of plasma proteins, this is known as facilitated transport. There is no input of ATP as the particles (such as glucose) are moving down the concentration gradient from the area of high concentration to the area of low concentration. Plasma proteins are sometimes needed if the particle is too big to fit through the membrane by itself, or if it is charged.
Active transport across a plasma membrane will occur when particles must be transported against the concentration gradient (from area of low concentration to area of high concentration). In this case the input of ATP is needed to pump the particles, using plasma proteins, against the concentration gradient.
