Diffusion, osmosis, and active transport (copy)

Diffusion

The movement of particles from high concentration to low concentration

Factors affecting the rate of movement of substances into and out of cells

1. Temperature

2. Distance

3. Large surface area to volume ratio

Temperature

It gives particles more kinetic energy so it moves faster, high rate of diffusion

Short diffusion distance

The shorter the distance, the faster the rate of diffusion

Large surface area to volume ratio

The larger the ratio, the faster the rate of diffusion

Process of osmosis

The passage of water moving from a medium of low conc to high conc solute through a semi-permeable membrane.

• high to low

• No ATP

Active transport

Movement particles from low to high concentration, it needs energy/ATP’s

against concentration gradient

Moving from low to high concentration

With concentration gradient

Moving from high to low concentration.

Concentration

Amount of solute dissolved within a solvent/solution

Hypertonic - Animal Cell

If an animal cell is placed into a hypertonic solution (more concentrated than the cytoplasm of the cell), it will lose water by osmosis and become shrivelled up. (plasmolysis)

• water potential of the cell cytoplasm is higher than the solution, so water will move outwards

Hypotonic - animal cell

• If an animal cell is placed into a hypotonic solution (more dilute than the cytoplasm of the cell), it will gain water by osmosis and will continue to do so until the cell membrane is stretched too far and it bursts

• water goes inside the cell

• water potential of the solution is higher than the cytoplasm, so water will move inwards

• cell swells till it burst

• this condition is called lysis.

Isotonic - Animal cell

Cell remains normal due to it containing equal solvent and solute both inside and outside the cellular membrane.

• net movement = 0

• there is no net movement of water. If it is slightly hypotonic or hypertonic, small movements will occur according to the gradient

• animals prefer to remain in this environment

Hypertonic - Plant cell

Cell membrane shrinks but nothing happens due to the cell wall’s rigidity, as water will leave the plant cell through its partially permeable cell surface membrane by osmosis

PLASMOLYSIS

Isotonic - Plant cell

Normal condition

• lost turgor pressure - flaccid

• no net movement of water

Hypotonic - Plant Cell

Water enters the cell through the cellular membrane with osmosis, but the cell will only inflate a little bit rather than bursting due to the rigidity of the cell wall.

• PLANTS PREFER TO REMAIN IN THIS ENVIRONMENT

• high turgid structure to keep structure upright

Passive diffusion

• directly through semi permeable membrane

• Things that are “small” and “non-polar” pass through easily

• No ATP

Facilitated

• Particles pass through protein channels (gate)

• “Polar” particles pass through (ex. water)

• No ATP.