osmosis

osmosis

the net movement of water from a dilute solution to a more concentrated solution through a partially-permeable membrane
1. the partially peremeable membrane
  1. Eg: water particles can move through pores in membrane but sugar particles (big) cant move through
  2. allows water molecules through
  3. stops solute molecules because they are too large
red blood cell in dilute solution - the cell would burst
1. red blood cell in concentrated solution - cell would shrink
  1. in a plant the cell would swell in dilute solution but not burst as it has a cell wall for protection
Active transport
1. root hair cells have large surface area
2. cells need to transport substances in and out
  1. (in) eg oxygen by diffusion for respiration from an area where theres a high concentration to lower concentration down a concentration gradient
    1. eg water by osmosis( can be in or out depending on concenration of the solutions inside and outside of the cell
  2. (in) glucose for respiration can go in by diffusion but we need active transport which requires energy ( can be moving against a concentration gradient )
3. The movement of particles/ions/molecules from an area of low concentration to an area of high concentration (against a concentraion gradient) energy from respiration is required
  1. substances are sometimes absorbed against a concentration gradient - in the opposite direction to normal disrtibution
    1. This requires energy from respiration.known as active transport
4. allows cells to absorb sugar ions that pass through cell membranes from very dilute solutions
  1. plants absorb ions from very dilute solutions in the soil by active transport
  2. in humans,sugar can be absorbed from the intestine and from the kidney tubules by active transport
concentration gradient is the region where the concenration of a substance varies from higher to lower
1. eg water moves from the soil into the plantsa root hair cells by osmosis along a concentration gradient
cell membrane controls particles that pass through as they have speacialised molecules to allow certain substnces through
sports drinks
1. blood sugar (glucose) needed for respiration that releases energy
  1. sweat - lose lots of water and mineral ions like sodium and potassium . if there are not enough mineral ion the cells work inefficiently
  2. the sugar used to relase energy during exerise
2. sports drinks can replace water, mineral ions and sugar

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