Active and Passive Transport

The main difference between active and passive transport is that active transport requires [blank_start]ATP[blank_end] and passive transport uses [blank_start]kinetic[blank_end] [blank_start]energy[blank_end].

Which of the following substances cross the plasma membrane by passive transport? Check all that apply.

Diffusion is a form of [blank_start]passive[blank_end] transport, requiring no [blank_start]ATP[blank_end]. It involves the movement of molecules from an area of [blank_start]high[blank_end] concentration, across a [blank_start]partially permeable[blank_end] membrane, to an area of [blank_start]low[blank_end] concentration. In other words, [blank_start]down[blank_end] the [blank_start]concentration gradient[blank_end]. The rate of diffusion depends on factors such as [blank_start]size[blank_end] of molecule, [blank_start]steepness[blank_end] of concentration gradient, [blank_start]temperature[blank_end], surface area, and diffusion [blank_start]distance[blank_end].

When transport requires no ATP, involves movement down a concentration gradient, and requires the aid of a transmembrane protein which changes conformation, this is a form of passive transport.

Osmosis is another word for diffusion.

Instead of talking about "water concentration", we normally refer to "[blank_start]water[blank_end] [blank_start]potential[blank_end]", which is the [blank_start]tendency[blank_end] of water molecules to [blank_start]diffuse[blank_end] from one [blank_start]region[blank_end] to another. Pure water has a water potential of (in digits) [blank_start]0[blank_end].

Water moves in and out of cells by [blank_start]osmosis[blank_end]. A plant cell with lots of water in it is [blank_start]turgid[blank_end], while [blank_start]cytolysis[blank_end] can be caused by too much water inside an animal cell. [blank_start]Plasmolysis[blank_end] occurs in plant cells when there is a [blank_start]low[blank_end] water potential in the cell and the cell membrane is [blank_start]drawn inwards[blank_end]. [blank_start]Crenation[blank_end] describes the shrinking of an animal cell with [blank_start]low[blank_end] internal water potential.

Which of the following statements are TRUE about active transport? Check all that apply.

Which of the following molecules are transport by bulk transport?

Phagocytosis describes a process where a cell [blank_start]ingests[blank_end] a foreign particle, usually one that is quite [blank_start]large[blank_end]. First, the cell changes shape and [blank_start]engulfs[blank_end] the foreign particle. Then, parts of the cell surface membrane at the extremes [blank_start]fuse together[blank_end] and form a [blank_start]vesicle[blank_end] around the foreign particle. Cells capable of this process are [blank_start]phagocytic[blank_end]. This is [blank_start]an active[blank_end] process.

Why is ATP needed for active transport and bulk transport? Check all that apply.