Name: ________________________
Pages: 73-75
Date: ____________________
BIOLOGY 12
DIFFUSION AND OSMOSIS
1) Compare the following terms:
a) diffusion vs. osmosis
Diffusion – the movement of molecules from a higher concentration to a lower
concentration
Osmosis – movement of water from an area of higher concentration to a lower
concentration across a semi-permeable membrane
Both involve movement from high to low concentration
b) solute vs. solvent vs. solution
solute – substance dissolved in a solvent to form a solution
solvent - liquid that dissolve a solute (i.e. water)
solution – solute (usually solid) + solvent (usually liquid)
c) osmotic pressure vs. concentration gradient
osmotic pressure – pressure created due to osmosis
concentration gradient – gradual decrease in concentration over a distance
2)
Explain what would
happen to the
concentrations of
water, glucose, and
copper sulphate on
side A of this
experiment.
Water will move to side A due to osmosis.
Side A [water] ↑
Copper sulphate ions will move to side A due to diffusion. Side A [ion] ↑
Glucose will not pass the membrane.
Side A [glucose] ↓
The opposite will occur on side B
3) Explain the difference between the terms isotonic, hypertonic and hypotonic.
Isotonic – a solution that has the same solvent and concentration as the cell
Hypertonic - a solution that has a greater solvent and concentration as the cell
Hypotonic. - a solution that has a lower solvent and concentration as the cell
4)
Amylase converts starch Æ glucose. Glucose is small enough to pass through
membrane but starch is too big. Also, H2O moves in by osmosis because [H2O] is
higher in the beaker than the tube.
5) Summarize what happens to ANIMAL CELLS placed in different tonicities of solution:
Tonicity of Solution Cell is Put Into
Isotonic
Net Movement of Water
No net movement
Effect on Cell
Remains the same
Hypotonic
Cell gains water
Cell Swells & May Burst
Cell loses water
“lysis”
Cell Shrinks
H2O
Hypertonic
H2O
“crenation”
6) Describe the difference between crenation and lysis.
crenation – hypertonic environment causes H2O to leave the cell causing it too
shrink
lysis - hypotonic environment causes H2O to enter the cell Æ turgor pressure
increases Æcausing the cell to swell and then burst
7) Summary of what happens to PLANT CELLS placed in different tonicities of solution:
Tonicity of Solution Cell is Put
Into
Isotonic
Net Movement of Water
Effect on Cell
No net movement
Remains the same
Hypotonic
Cell gains water
Greater water pressure inside
cell
H2O
Hypertonic
Cell loses water
“turgor pressure”
Cell Contents Shrink, but cell
wall retains its shape
H2O
“plasmolysis”
8) Compare osmotic pressure and turgor pressure.
osmotic pressure – pressure caused by the flow of water across a
semipermeable membrane
turgor pressure – internal pressure within a cell due to the inward flow of
water due to osmosis
9) What are the similarities and differences between crenation and plasmolyis?
Similar – water moves out of the cell and cytoplasm shrinks
Difference – plant cells undergo plasmolysis but they do not collapse completely
due to the cell wall.