Chap3 movement of substances

1. Chapter 3: Movement of
Substances

2. Lesson Objectives
(a) define diffusion and discuss its importance in
nutrient uptake and gaseous exchange in plants and
humans.
(b) define osmosis and discuss the effects of osmosis
on plant and animal tissues.
(c) define active transport and discuss its importance as
an energy-consuming process by which substances
are transported against a concentration gradient, as
in ion uptake by root hairs and uptake of glucose by
cells in the villi.

3. Methods of Transport Across Membranes
1. Diffusion
2. Osmosis
3. Active Transport

4. What did we observe?

5. 3.1 Diffusion
• substances will move from where it is more
concentrated to where it is less
concentrated, down its concentration
gradient.
• Diffusion is defined as the random
movement of particles down a
concentration gradient
• Energy is not required

6. 3.1 Diffusion
• Concentration
gradient
= The difference in
concentration
between two regions
• The steeper the
concentration for a
substance, the faster
the rate of diffusion

7. 3.1 Diffusion
• Each substance
diffuses down its own
concentration
gradient, independent
of the concentration
gradients of other
substances.

8. Thinking Questions!
• What is (i) a natural and
(ii) an artificial example of
a partially permeable
membrane?
• Can diffusion occur across
a partially permeable
membrane?
• Can all particles move
across a partially
permeable membrane?

9. Research Questions!
• Describe how diffusion occurs in animals.
a) movement of food substances across
the walls of small intestines into blood
b) movement of dissolved food
substances and oxygen from blood into
tissue fluid and into cells
c) movement of carbon dioxide from
blood into air spaces (in the lungs) and
vice versa for oxygen

10. Research Questions!
• Describe how diffusion occurs in plants.
a) movement of carbon dioxide into the
leaf through the stomata during the day
and vice versa for oxygen at night
b) movement of water vapour out of the
leaf through the stomata during
transpiration
c) movement of mineral salts into the
root hair cells

11. Factors that increases rate of diffusion
Conditions which increase the rate of diffusion
(1) Steeper concentration gradient
(2) The shorter the distance over which diffusion occurs,
the faster the diffusion rate
(3) Greater surface area to volume ratio
(4) Larger number of pores and greater numbers of
pores (if partially permeable membrane is present)
(5) Smaller and lighter molecules
(6) The higher the temperature, the greater the speed of
motion of the particles

12. 3.2 Osmosis

13. 3.2 Osmosis
• Water molecules will move from where it is more
concentrated to where it is less concentrated,
down its water potential gradient.
• Osmosis is defined as
the NET movement of
water molecules down
a water potential gradient
across a partially
permeable membrane

14. 3.2 Osmosis
• Water potential = a measure of the tendency of
water molecules to move from one place to
another
• direction of osmosis is determined only by a
difference in total solute concentration

15. 3.2 Osmosis – Types of solutions
• 3 types of solutions:
– solution with the higher concentration of solutes is
hypertonic.
– solution with the lower concentration of solutes is
hypotonic.
– Solutions with equal solute concentrations are isotonic

16. How does osmosis affects cells?

17. How does osmosis affects cells?

18. How does osmosis affects cells?

19. How does osmosis affects cells?

20. How does osmosis affects cells?

21. How does osmosis affects cells?

22. Importance of Turgor pressure
• Helps to support the soft tissues of plants so
that they remain firm
• Absence of turgor in cells results in plant cells
becoming flaccid (soft)  plant will wilt
• Causes the opening and closing of the stomata
• Causes the opening and closing of flowers

24. How does osmosis
affects cells?

25. Active Transport
• Substances move against their concentration
gradient, from the side where they are less
concentrated to where they are more
concentrated.
• Requires ENERGY

26. Comparing Diffusion and Active Transport

27. Research Questions!
• Describe where active transport occurs
in humans.
a) in small intestine during the uptake of
food substances
• Describe where active transport occurs
in plants.
a) in roots during the uptake of mineral
salts

28. Processes
Diffusion Osmosis
• Refers only to water molecules
• Takes place across a partially
permeable membrane
Similarities
• Energy not required
• Movement of substances down
a concentration gradient
• Refers to any substance,
gaseous or liquid
• Membrane is not required
Movement of Substances Into or Out of Cells
Differences

29. Movement of
particles
(molecules or
ions) against a
concentration
gradient.
Energy is
required.
Movement of
particles
(molecules or
ions) down a
concentration
gradient.
Processes
Diffusion Osmosis
Net movement of water
molecules across a
partially permeable
membrane, from a
solution of higher water
potential to a solution of
lower water potential.
Active
Transport
Movement of Substances Into or Out of Cells

30. Thinking Question
• Give students a teabag in water scenario. Ask
them what happens?

31. Scenario 1
It was a fine sunny day, and Mr Q was driving to work as
usual. He was drinking his favorite icy cold Coke drink
when…
Suddenly!!!
A car came from nowhere and bang into Mr Q’s car!
!!!!!!!!!!
One of Mr Q’s finger was CHOPPED OFF!
You happen to walk past, and full of integrity (hopefully..),
you ran as fast as you can to his help!
You quickly throw his severed finger into the drink to
preserve the finger, so that the doctor can mend it back.
Is this the right thing to do? Why???

32. Scenario 2
It was a fine sunny day, and Mr Viresh was out sun-tanning in
his yacht.
Suddenly!!!
A strong gush of tsunami came and blew his yacht far far
away!
!!!!!!!!
Mr V landed on a deserted island with no one but himself!!!
He peed so much out of fear that he feels so dehydrated…
He started drinking the seawater to hydate
himself.
Is that the right thing to do??? Why???