osmosis

• PARTIALLY PERMEABLE MEMBRANE

  Has tiny holes that allow only small molecules like water to pass through, preventing larger molecules like proteins and sucrose from moving across.

  
• Root hair cells are specialised for absorbing water and minerals and they use osmosis to take in WATER from the soil as there is a higher water concentration outside in the soil, causing water particles to pass into the cell where there is a lower water concentration.

  
• Because the concentration of sugar in the bag was higher than in the drink, so the water moved in by osmosis.

  
• B would be expected to show the smallest change in mass because its the closest to the concentration to 5%, so less water moves in.

  
• Osmosis


  It's a passive process of water moving from a high water concentration to a lower water concentration through a partially permeable membrane.

  
• • water enters the potato by osmosis.
  • water moves in through the cell wall as it is absorbent.
  • water moves in through cell membrane as it is partially permeable and allows water to pass
  • concentration of salt solution in cytoplasm is greater than 0.2 mol/dm^3, so water moves from a higher water concentration to a lower water concentration.

  
• The Osmosis Experiment

  Investigating the effect of different concentrations of sugar solution on plant tissue.
• The Osmosis Experiment

  Sample Method:

  1. Cut some cylinders of potato tissue and measure their mass.
  2. Place the cylinders in different concentrations of sugar solution.
  3. After about 30 mins remove the cylinders and measure their mass again.

  If the cylinders change in mass, they have gained or lost water by osmosis.

  
• The Osmosis Experiment

  Analysing Results

  • If cylinders in sugar solutions GAIN mass, water has moved INTO the cells by osmosis, showing that the solutions had a HIGHER WATER CONCENTRATION than the inside of the potato. 

  
• The osmosis experiment

  Analysing results:

  • If cylinders in sugar solutions LOSE mass, water has moved OUT OF the cells by osmosis, showing that the solutions had a LOWER WATER CONCENTRATION than the inside of the potato. 

  
• The osmosis experiment

  Analysing results:

  • If cylinders in sugar solutions did not change, then the solutions had the SAME WATER CONCENTRATION as the inside of the potato. 

  
• The osmosis experiment variables:

  • (Same) CONTROLLED VARIABLE: the volume of the solution, temperature, time, and type of sugar/salt.
  • (Alter) INDEPENDENT VARIABLE: the sugar solution concentration.
  • (Measure) DEPENDENT VARIABLE: the MASS of the potato cylinders

  
• The osmosis experiment - Calculating results

  • The effect of the sugar solution on osmosis can be measured by calculating the PERCENTAGE CHANGE in mass for each sugar concentration. 

  A) 16.2%

  
• percentage change in mass = ( change in mass / original mass ) x 100
• So only the mass of the potato is measured.

  
• changes to expect in the potato in tube A after 2 hrs:

  • increase in mass
  • increase in length

  
• • water would move inside the potato cells in tube A.
  • the solution outside the potato in tube A is at a lower concentration than the solution inside the potato cells.

  
• Two of the numbers for the change in mass have a negative value, this means that the potato lost mass.

  
• yes because the mass change is much lower than the others.

  
• The student could modify the investigation to determine the concentration of the solution inside each egg by:

  Using five different concentrations of salt solutions by plotting percentage change on a graph and determine the concentration where the line crosses the 0 percentage change.

  
• Flaccid


  when the vacuole shrinks
• Turgid


  When the vacuole expands
• Iso- (Isotonic)

  Equals to
• Hyper- (Hypertonic - more solute, less water)


  Over and above, excessive
• Hypo- (Hypotonic - less solute, more water)


  under, below normal
• How do plant cells react to osmosis?

  When there's too much water, the vacuole would expand so much that it's squashing the cell membrane to the cell wall.

  This is called turgid.

  
• How do plant cells react to osmosis?

  When there's too little water, the vacuole and cytoplasm would shrink from cell wall.

  this is call flaccid.

  
• How do animal cells react to osmosis?

  If there's too little water, the red blood cell will shrivel up, this is called crenation.

  
• How do animal cells react to osmosis?

  If there's too much water, the red blood cell will burst, this is called lysis.

  
• Dilute

  less solute, more water

  
• Concentrated

  more solute, less water