Page 74 - Demo 1

Figure 34. Channel proteins and carrier proteins help substances diffuse across a cell
membrane. In this diagram, the channel and carrier proteins are helping
substances move into the cell (from the extracellular space to the
intracellular space).
Source:
https://dr282zn36sxxg.cloudfront.net/datastreams/f-d%3A0a1885b40dacc874eeaedfc4909079bd094866efa013774
ee6da168a%2BIMAGE_TINY%2BIMAGE_TINY.1

Osmosis
Diffusion permits the passage of molecules like oxygen, carbon dioxide,
and non-polar lipids through the cell membrane. Osmosis is a special type of
diffusion. It is the diffusion of water molecules across a selecvely permeable
membrane. Like other molecules, water moves from an area of higher
concentraon to an area of lower concentraon. Water moves in or out of a cell
unl its concentraon is the same on both sides of the cell membrane.

When solutes are added to a cell’s surroundings, its selecvely
permeable membrane usually limits the passage of the solute back and forth.
Instead, osmosis allows water to move back and forth across the membrane,
affecng the size and shape of cells.

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