Transcript solute

Diffusion, Osmosis, and
Algae!
Filamentous Algae under normal
conditions
even distribution of
chloroplasts – from cell
wall to cell wall
Plant cells in salt solution
• Cell membranes
pull away from the
cell wall
• Chloroplasts
appear to cluster in
the center of the
cell.
Plant cells in distilled water
•
between
chloroplasts
S
p a c e
Chloroplasts
spread out
across cell
•
•Small space
between
adjacent cells.
Why these differences in
appearance?
Osmosis
• Water has DIFFUSED into some of these
cells making them expand.
Water has DIFFUSED out of some of these
cells making them shrink.
Osmosis
• When placed in ISOTONIC,
HYPERTONIC, or HYPOTONIC solution,
water will diffuse across the cell
membrane.
• The diffusion of water across a cell
membrane is called OSMOSIS.
When does diffusion stop?
BRIEF REVIEW:
• Solutions are mixtures
• Particles are evenly distributed throughout
the mixture.
• The particles are the SOLUTE (solid stuff),
the liquid it is mixed in is the SOLVENT
(liquid stuff – usually water)
Now, Back To Work!
ISOTONIC SOLUTIONS
• ISO –SAME; TONIC – SOLUTION
• Occurs when the concentration of solute
(solid) and solvent (liquid) inside and
outside the cell are the same.
•C e lls a p p e a r “ n o r m a l
S o lv e n t 8 0 %
S o lv e n t 8 0 %
S o lu te 2 0 %
S o lu te 2 0 %
=
C e ll
S o l u t io n
HYPERTONIC
• HYPER – ABOVE; TONIC – SOLUTION
• Occurs when the solute concentration in
the surrounding solution is higher than
the concentration in the cells.
• Cells appear to shrivel or shrink.
S o lv e n t 8 0 %
S o lv e n t 9 0 %
S o lu te 2 0 %
S o lu te 1 0 %
>
C e ll
C e ll
S o l u t io n
HYPOTONIC
• HYPO – LOW; TONIC – SOLUTION
• Occurs when the solute concentration in
the surrounding solution is lower than the
concentration in the cells.
• Cells appear to expand.
S o lv e n t 9 0 %
S o lv e n t 8 0 %
S o lu te 1 0 %
S o lu te 2 0 %
<
C e ll
S o l u t io n
C e ll
Osmosis
• When placed in a HYPERTONIC solution,
water moves from inside the cell to the
surrounding solution.
• It moves from HIGH concentration (inside
the cell) to LOW concentration (outside the
cell).
low
low
high
low
same
same
low
E q u il ib r iu m
re a c h e d !
Osmosis
• When water moves out of a cell, water
pressure decreases.
• The decrease in pressure allows the cell
membrane to pull away from the cell wall.
• The organelles appear to cluster in the
center of the cell.
• This is PLASMOLYSIS.
Write a definition for plasmolysis
in your own words.
Osmosis
• When placed in a HYPOTONIC solution,
the water moves from the surrounding
solution into the cell.
• It moves from HIGH concentration (outside
the cell) to LOW concentration (inside the
cell). high
same
high
same
low
high
high
E q u il ib r iu m
re a c h e d !
Osmosis
What about ISOTONIC solutions?
• Molecules are always moving.
• Water moves in and out equally.
same
same
Let’s try some practice!
Experimental
Set ups
Demonstrating
Osmosis
Higher WATER
concentration
Lower WATER
concentration
Beaker
contains tap
water and
bag contains
20 % NaCl
In the set up does
the water in the
narrow tube rise, fall
down or shows no
change? In which
direction has the
water moved?
Is this a Hypertonic, Hypotonic,
or Isotonic solution?
Water
moves from
beaker to
bag!
Beaker and bag
contain 20 %
NaCl
In this set up does the
water in the narrow tube
rise, fall down, or shows
no change? In which
direction has the water
moved?
Net movement of
water is the same
(going both IN and
OUT, therefore
overall no
Is this a Hypertonic, Hypotonic,
or Isotonic solution?
movement of water
is seen.
Higher
WATER
concentration
Lower WATER
concentration
Beaker
contains25 %
NaCl and bag
contains 20 %
NaCl
In this set up does
the water in the
narrow tube rise, fall
down or shows no
change? In which
direction has the
water moved?
Water moves
from bag into
Is this a Hypertonic, Hypotonic,
beaker
or Isotonic solution?
On your illustrations from
yesterday:
• Label the HYPERTONIC solution
HYPOTONIC solution
ISOTONIC solution
• Draw arrows on each illustration to show
which direction the water is moving
• Label the illustration that shows
PLASMOLYSIS