Download Osmosis - BACA GCSE

Osmosis
Learning Objective
To know osmosis is the diffusion of water from a
dilute sugar solution to a more concentrated
sugar solution through a partially permeable
membrane.
To be able to work in a group to produce primary
data from experimental work
To be able to analyse the data and produce a
line of best fit graph.
To be able to draw conclusions from your
analysis of the data
To be able to evaluate the experiment.
Success Criteria
• All can carry out the practical work to obtain
primary data.
• All can describe the movement of water across a
partially permeable membrane by osmosis.
• Most can analyse the data and draw a line of
best fit graph.
• Most can draw valid conclusions based on the
data and knowledge of osmosis.
• Some can evaluate the experiment.
• Some can explain in detail how water moves
down a concentration gradient from a high
concetration of water to a low concentration of
water.
What is osmosis?
Osmosis is the diffusion of
water molecules from a low
sugar concentration solution
to high sugar concentration
solution, across a partiallypermeable membrane.
• Osmosis is passive and requires
no energy.
• It is the NET movement of water
molecules across a partially
permeable membrane
Dilute vs. concentrated
During osmosis, water molecules diffuse from pure water or
dilute solution to more concentrated solutions.
 Dilute solutions have a high concentration of
water molecules.
 Concentrated solutions have a low concentration
of water molecules.
pure water
dilute solution
concentrated
solution
Predicting osmosis
Osmosis in action
Osmosis and cells
Plant and animal cells are surrounded by a partiallypermeable plasma membrane. This allows water and other
small molecules to diffuse across.
Plant cells additionally have a strong cell wall surrounding
the membrane which offers support and protection.
plasma
membrane
cell wall
plant cell
red blood cell
Osmosis and plant cells
Osmosis and animal cells
Animal cells do not have a cell wall. This means they
respond differently to plant cells to the gain and loss of
water.
In dilute solutions, osmosis can
cause animals cells, such as red
blood cells, to swell up and burst.
This is called lysis.
In concentrated solutions, water
loss causes the cells to shrink.
When this happens to red blood
cells, it is called crenation.
Osmosis and animal cells
Osmosis and animal cells
In order to remain healthy, animal cells need to maintain
an isotonic water balance. This means that the water
concentration both inside and outside the cell are equal.
hypothalamus
The concentration of water
and salt in the blood are
controlled by the kidneys.
The kidneys are controlled
by the portion of the brain
called the hypothalamus.
Anagrams