Movement of substances

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Osmosis

Osmosis

Defininition: The movement of water particles from a high water potential to a low water potential across a partially permeable membrane 

Impact on animal cells: If an animal cell is placed in a salt solution, the water will travel out of it (high to low W.P.) and it will become flaccid. If it is placed in water, the water will travel into it and it will swell and burst (has no cell wall)

Impact on animal cells: If placed in a water solution, it will become flaccid as the water travels out. If placed in water, it will become turgid but will not burst because of the cell wall. Plant cells need to be turgid because it provides support to keep the plant upright. 

Affected by:

  • S.A. to volume ratio (the larger the surface area and the smaller the volume, the faster)
  • Temperature (particles have more energy...or less!)
  • Concentration (more particles therefore faster osmosis)
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Diffusion

Diffusion

Defininition: The random movement of particles from an area of high concentration to an area of low concentration

Impact on animals: Allows breathing in mammals; gases diffuse through the walls of the alveoli; in digestion, important nutrients diffuse through the intestine walls.

Impact on plants: Allows photosynthesis; gases diffuse in/out through the stomata and are absorbed by the plant

Affected by:

  • S.A. to volume ratio (the larger the surface area and the smaller the volume, the faster)
  • Temperature (particles have more energy...or less!)
  • Concentration (more particles therefore faster diffusion)
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Active Transport

Active transport

Defininition: the process by which dissolved molecules move across a cell membrane from a lower to a higher concentration (against concentration gradient) and requires an input of energy

Impact on animals: In humans, active transport takes place during the digestion of food, where broken down carbs (simple sugars) are actively transported by the villi into the bloodstream.

Impact on plants: Root hair cells actively transport minerals from the soil to the plant

Affected by:

  • Energy of carrier molecules
  • Temperature (particles have more energy...or less!)
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Active Transport

Active transport

Defininition: the process by which dissolved molecules move across a cell membrane from a lower to a higher concentration (against concentration gradient) and requires an input of energy

Impact on animals: In humans, active transport takes place during the digestion of food, where broken down carbs (simple sugars) are actively transported by the villi into the bloodstream.

Impact on plants: Root hair cells actively transport minerals from the soil to the plant

Affected by:

  • Energy of carrier molecules
  • Temperature (particles have more energy...or less!)
4 of 4

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