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Movement
of
Substances
Learning Outcome
• Define diffusion and describe the role of diffusion
in nutrients uptake and gaseous exchange in plants
and humans.
• Define osmosis and describe the effects of osmosis
on plant and animal tissues.
• Define active transport and discuss its importance
as an energy-consuming process (Pure)
Diffusion
• Diffusion is the net movement of molecules
from a region of higher concentration to a
region of lower concentration, down a
concentration gradient.
• Concentration gradient??
• Difference in concentrations of the substance between
Diffusion
Moving molecules
In which states are molecules able to diffuse?
Molecules in liquids and gases are constantly moving and bumping into each
other. This means that they tend to spread out.
gas (e.g. steam)liquid (e.g. water)solid (e.g. ice)
Diffusion in action: two gases
Diffusion in action: one gas
Dissolved substance diffuse throughout liquid in
which they are dissolved.
Diffusion
• Can starch diffuse
through the partially
permeable membrane?
• Can glucose diffuse
through the partially
permeable membrane?
Examples of diffusion
• Carbon dioxide diffuses from blood
capillary into alveoli and oxygen
diffuses from alveoli into surrounding
blood capillaries.
• The diffusion of carbon dioxide
through the stomata into the
mesophyll cells.
• The diffusion of water vapour from
the leaves during transpiration.
Diffusion: true or false?
Osmosis
•the net movement of water molecules
•from a region of higher water potential to a
region of a lower water potential
•through a partially permeable membrane
•Involves only water molecules
Concentrated Vs. Diluted
Solution A Solution B
1. 10% salt solution 2% salt solution
2. 80% sugar solution 100% distilled water
3. 50% salt solution 50% salt solution
Which direction would osmosis occur?
Osmosis in action!
Partially permeable membrane
Osmosis in Action!
Diffusion Osmosis
Both involve the movement of molecules
from a region of higher concentration
to a region of lower concentration
How are they alike?
1. Involves movement of
all types of molecules.
2. Do not involve a
partially permeable
membrane
1. Involves movement of only
water molecules
2. Involve the movement of
water molecules passing
through a partially
permeable membrane
How are they different?
Osmosis in Living Cells
•Animal Cell
•Plant Cell
What happens when water enters
an Animal Cell
Animal cell swells and
may burst.
Why?
Due to the
absence of a
cell wall.
What happens when water enters
a Plant Cell
Plant cell swells and
becomes turgid w/o
bursting.
Why?
Due to the
presence of a
cell wall.
What happens when water exits
an Animal Cell
Little spikes appear on the
plasma membrane. This
process is called
crenation.
The animal
cell
shrinks.
What happens when water exits
a Plant Cell
Vacuole decreases in size
and cell becomes soft and
flaccid.
What happens to
the plant?
The plant
• Therefore turgor pressure is
important
• To help maintain the shape of
tissues in plants
Wilts
MicroQues 3
Four plant cells were placed in 20% sucrose solution, 50% sucrose
solution, 80% sucrose solution and pure water separately.
In the table below,
(a) describe the appearance of the plant cells.
(b) identify the solution that the cells have been placed in.
Pure water
20% sucrose 50% sucrose 80% sucrose
Cell become
turgid.
No change. Cell become
flaccid.
Cell become
plasmolysed.
MicroQues 3
Lets Recap!
• What is diffusion?
• Name some examples of diffusion
• What is osmosis?
• Name some examples of osmosis
• What happens when an animal cell is placed into a
concentrated sugar solution?
• What happens when an animal cell is placed into
distilled water?
Lets Recap!
• What happens when a plant cell is placed into a
concentrated sugar solution?
• What happens when a plant cell is placed into
distilled water?
Lets Recap!
… Any other modes of transportation?
Besides diffusion & osmosis?
Active
Transport!
Active Transport
• Requires energy
• When substances move from a region of lower
concentration to a region of higher concentration
against a concentration gradient
• Occurs only in living cells as only living cells respire
• Respiration will release energy where part of it will
be used in active transport
Active transport is the process in which particles
move from a region of low concentration to a
region of high concentration, against the
concentration gradient, with the use of energy.
Lets recall…. In Sec 2…
Some examples of active transport
• The absorption of mineral salts from the surrounding
soil solution by root hair cells.
• The absorption of glucose and amino acids by the
epithelium cells in the small intestines of man, when
they are low in concentration.
Which of the following diagram illustrates the most likely
appearance of a red blood cell that has been placed in
distilled water?
Micro Ques 4
( D )
A strip of potato, originally 50 mm in length, was measured
after it was soaked in distilled water. Which of the following
graphs A, B, C or D best represents the results?
Micro Ques 5
( A )
length of potato
strips/mm
The apparatus shown in the diagram was set up. After one
hour, the water in the beaker turned red. What is the most
likely reason for this colour change?
Micro Ques 6
A Molecules of red ink move through the membrane by diffusion.
B Molecules of red ink move through the membrane by osmosis.
C Molecules of water move through the membrane by diffusion.
D Molecules of water move through the membrane by osmosis.
( A )
Factors affecting the rate of movement
of substances
Surface Area to Volume
Ratio
Surface Area to Volume Ratio
• Surface Area: measure of how much exposed area a
solid object has, expressed in square units (x2).
• Volume: how much three-dimensional space a
substance (solid, liquid, gas, or plasma) or shape occupies
and is expressed in cubed units (x3).
• Ratios (Surface Area:Volume):
make comparisons between two things.
Surface area and volume
Have you ever wondered why our body has such a
dense network of blood capillaries?
To increase the SA : Vol for faster rate of diffusion
Start working on your
Assignment
To-dos

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Movement of substances

  • 2. Learning Outcome • Define diffusion and describe the role of diffusion in nutrients uptake and gaseous exchange in plants and humans. • Define osmosis and describe the effects of osmosis on plant and animal tissues. • Define active transport and discuss its importance as an energy-consuming process (Pure)
  • 3. Diffusion • Diffusion is the net movement of molecules from a region of higher concentration to a region of lower concentration, down a concentration gradient. • Concentration gradient?? • Difference in concentrations of the substance between
  • 5. Moving molecules In which states are molecules able to diffuse? Molecules in liquids and gases are constantly moving and bumping into each other. This means that they tend to spread out. gas (e.g. steam)liquid (e.g. water)solid (e.g. ice)
  • 8. Dissolved substance diffuse throughout liquid in which they are dissolved.
  • 9. Diffusion • Can starch diffuse through the partially permeable membrane? • Can glucose diffuse through the partially permeable membrane?
  • 10. Examples of diffusion • Carbon dioxide diffuses from blood capillary into alveoli and oxygen diffuses from alveoli into surrounding blood capillaries. • The diffusion of carbon dioxide through the stomata into the mesophyll cells. • The diffusion of water vapour from the leaves during transpiration.
  • 12. Osmosis •the net movement of water molecules •from a region of higher water potential to a region of a lower water potential •through a partially permeable membrane •Involves only water molecules
  • 13. Concentrated Vs. Diluted Solution A Solution B 1. 10% salt solution 2% salt solution 2. 80% sugar solution 100% distilled water 3. 50% salt solution 50% salt solution Which direction would osmosis occur?
  • 14. Osmosis in action! Partially permeable membrane
  • 16. Diffusion Osmosis Both involve the movement of molecules from a region of higher concentration to a region of lower concentration How are they alike? 1. Involves movement of all types of molecules. 2. Do not involve a partially permeable membrane 1. Involves movement of only water molecules 2. Involve the movement of water molecules passing through a partially permeable membrane How are they different?
  • 17. Osmosis in Living Cells •Animal Cell •Plant Cell
  • 18. What happens when water enters an Animal Cell Animal cell swells and may burst. Why? Due to the absence of a cell wall.
  • 19. What happens when water enters a Plant Cell Plant cell swells and becomes turgid w/o bursting. Why? Due to the presence of a cell wall.
  • 20. What happens when water exits an Animal Cell Little spikes appear on the plasma membrane. This process is called crenation. The animal cell shrinks.
  • 21. What happens when water exits a Plant Cell Vacuole decreases in size and cell becomes soft and flaccid. What happens to the plant?
  • 22. The plant • Therefore turgor pressure is important • To help maintain the shape of tissues in plants Wilts
  • 23. MicroQues 3 Four plant cells were placed in 20% sucrose solution, 50% sucrose solution, 80% sucrose solution and pure water separately. In the table below, (a) describe the appearance of the plant cells. (b) identify the solution that the cells have been placed in.
  • 24. Pure water 20% sucrose 50% sucrose 80% sucrose Cell become turgid. No change. Cell become flaccid. Cell become plasmolysed. MicroQues 3
  • 25. Lets Recap! • What is diffusion? • Name some examples of diffusion • What is osmosis? • Name some examples of osmosis
  • 26. • What happens when an animal cell is placed into a concentrated sugar solution? • What happens when an animal cell is placed into distilled water? Lets Recap!
  • 27. • What happens when a plant cell is placed into a concentrated sugar solution? • What happens when a plant cell is placed into distilled water? Lets Recap!
  • 28. … Any other modes of transportation? Besides diffusion & osmosis? Active Transport!
  • 29. Active Transport • Requires energy • When substances move from a region of lower concentration to a region of higher concentration against a concentration gradient • Occurs only in living cells as only living cells respire • Respiration will release energy where part of it will be used in active transport
  • 30. Active transport is the process in which particles move from a region of low concentration to a region of high concentration, against the concentration gradient, with the use of energy.
  • 31. Lets recall…. In Sec 2… Some examples of active transport • The absorption of mineral salts from the surrounding soil solution by root hair cells. • The absorption of glucose and amino acids by the epithelium cells in the small intestines of man, when they are low in concentration.
  • 32. Which of the following diagram illustrates the most likely appearance of a red blood cell that has been placed in distilled water? Micro Ques 4 ( D )
  • 33. A strip of potato, originally 50 mm in length, was measured after it was soaked in distilled water. Which of the following graphs A, B, C or D best represents the results? Micro Ques 5 ( A ) length of potato strips/mm
  • 34. The apparatus shown in the diagram was set up. After one hour, the water in the beaker turned red. What is the most likely reason for this colour change? Micro Ques 6 A Molecules of red ink move through the membrane by diffusion. B Molecules of red ink move through the membrane by osmosis. C Molecules of water move through the membrane by diffusion. D Molecules of water move through the membrane by osmosis. ( A )
  • 35. Factors affecting the rate of movement of substances Surface Area to Volume Ratio
  • 36. Surface Area to Volume Ratio • Surface Area: measure of how much exposed area a solid object has, expressed in square units (x2). • Volume: how much three-dimensional space a substance (solid, liquid, gas, or plasma) or shape occupies and is expressed in cubed units (x3). • Ratios (Surface Area:Volume): make comparisons between two things.
  • 38. Have you ever wondered why our body has such a dense network of blood capillaries? To increase the SA : Vol for faster rate of diffusion
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