chp 2: movement of substances [pure bio OLVL]

definition of diffusion

the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient

definition of osmosis

the net movement of water molecules from a solution of higher water potential to a solution of lower water potential, through a partially permeable membrane

definition of active transport

an energy consuming process by which substances (solutes or ions) are transported against a concentration gradient from a region of lower concentration to a region of higher concentration

what is a hypotonic solution?

has a higher water potential than the inside of the cell

what is an isotonic solution?

has the same water potential as the inside of the cell

what is a hypertonic solution?

has a lower water potential than inside of the cells

animal cell in a hypotonic solution

- cell cytoplasm has a lower water potential as compared to the solution
- more water molecules will enter the cell by osmosis through the PPM
- cell enlarges/swells and bursts/ ruptures (no cell wall--> bursts)

animal cell in an isotonic solution

cell remains the same size and volume

animal cell in a hypertonic solution

- cell cytoplasm has a higher water potential as compared to the solution
- more water molecules will leave the cell by osmosis through the PPM
- cell shrinks (crenation: little spikes like covid) --> crenated
- the cell will become dehydrated and eventually die

plant cell in a hypotonic solution

- the cell (sap) has a lower water potential than the solution outside of the cell
- as water enters the cell via osmosis. the vacuole increases in size and pushes the contents of the cell against the cell wall
- the strong cell wall prevents the over-expansion (bursting??) of the cell by exerting an opposing pressure as water enters the cell
- this prevents entry of more water
- the cell enlarges and becomes turgid
(pressure exerted by water in the cell is turgor pressure)

plant cell in an isotonic solution

cell remains the same size and volume

plant cell in a hypertonic solution

- the cell (sap) has a higher water potential than the solution outside of the cell
- as water leaves the cell via osmosis. the vacuole decreases in size and the volume of the cytoplasm decreases
- the cell becomes flaccid
- as the cell loses more water, the cytoplasm shrinks and the cell membrane tears away from the cell wall
- this is known as plasmolysis