Osmosis and Diffusion
Passive Transport
Osmosis and Diffusion
• Terms and definitions
Osmosis and Diffusion
• 1.Diffusion - the process by which
molecules spread from areas of high
concentration, to areas of low
concentration
Osmosis and Diffusion
• 1.Diffusion
– eventually spreading out evenly into the
available space
Osmosis and Diffusion
• Several factors can affect the
rate the diffusion……
• One such factor is temperature
• Higher temperatures tend to
increase the rate of diffusion
Osmosis and Diffusion
• 2.Solutes- a substance dissolved in fluid
Ex: Salt is a solute, when it is concentrated
inside or outside the cell, it will draw the
water in its direction
This is also why you get thirsty after eating something salty
Osmosis and Diffusion
• 3.Solvent - is a liquid, solid, or gas that
dissolves another solid, liquid, or gaseous
solute
– resulting in a solution
Osmosis and Diffusion
4.Osmosis
A specialized type of diffusion
is the movement of a solvent
(frequently water) through a
semi-permeable membrane
Osmosis is a type of a process where a fluid passes through
a semipermeable membrane and moves from an area where
a solute is present in low concentrations to an area where a
solute is present in a higher concentration
Osmosis
• http://www.youtube.com/watch?v=sdiJtDRJQEc
Osmosis is a type of a process where a fluid passes through a
semi-permeable membrane, from a higher concentration of water
to a lower concentration of water
Osmosis and Diffusion
• 5.Tonicity is a measure of the osmotic
pressure gradient when comparing the
concentration of solutes in different
solutions & the following terms are used:
Osmosis and Diffusion
• Hypotonic Solutions:
• contain a low concentration of
solute (more water)
• When a cell is placed in a
hypotonic solution, the water
diffuses into the cell, causing the
cell to swell
• Hint : po boy sandwich
Osmosis and Diffusion
• Hypertonic Solutions:
• contain a high concentration of
solute (less water)
• When a cell is placed in a
hypertonic solution, the water
diffuses out of the cell, causing the
cell to shrivel
• Hint: Hyper kids
Osmosis and Diffusion
• Isotonic Solutions: contain
the same concentration of solute
( equal amounts of water)
• When a cell is placed in an isotonic
solution, the water diffuses into and
out of the cell at the same rate
• The fluid that surrounds the body
cells is isotonic
Osmosis and Diffusion
• In the real world……….
– In humans, osmosis occurs in the kidneys to recover the water
form waste materials of the body. The kidneys regulate the
concentration of water in the blood plasma.
– Kidney dialysis
Osmosis and Diffusion
• In the real world
In plants, osmosis occurs for example
at root hairs, allowing the uptake of water
from the soil.
For today
• 6.1 - DEMO
The effects of size and temp on diffusion
– Agar that is in its gel state is porous, thus
making it easier for solutions to spread.
After 30 mins…..
» Measuring “Halos”
For Today
• 6.2 You begin here
Effect of solute concentration on osmosis
10% sucrose
dH20
Read materials and methods & FOLLOW DIRECTIONS
40 minutes
For Today
• 6.3
Selective permeability of membranes
– 6 solutions – one per bench
– SHARE DATA
40 minutes
AGAIN….Read materials and methods & FOLLOW DIRECTIONS
For Today
• 6.4
Osmosis with red blood cells (lack cell walls)
» RBC in isotonic solution
» Plump round cells
RBC in hypertonic solution
For Today
• 6.5
Osmosis with plant cells (cell walls)
Plasmolysis - cytoplasm pulls away from
the cell wall due to the loss of water
through osmosis
Hypertonic
Hypotonic
For Today
• Goggles
• Waste
• Chemicals
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Silver nitrate
Barium chloride
Gram’s iodine
Biuret
Benedict’s
Blood
PRACTICAL NEXT WEEK
• Starts promptly at
8:30am
• Must have note from
doctor for a make-up
• Review on website
• Contact me before
8:30am for help
• GOOD LUCK