3. Learning Outcomes for Section 1
At the end of this lesson, you should be able to:
observe and infer that diffusion is the movement of
molecules from a region of higher concentration
observe and infer that osmosis involves the movement
of water molecules when two solutions of unequal
concentration are separated by a partially permeable
membrane
explain how diffusion and osmosis are involved in the
transport system
explain the need for a transport system in multicellular
organisms
3
5. How can we smell rubbish?
Smell come from vapour from the
rubbish.
Particles in the vapour move
about randomly.
They bump into each other and
spread out quickly.
Some of the particles enter our
nostrils.
The spreading out of particles is
brought about by diffusion.
5
6. Diffusion
Diffusion is the movement of particles from a region
of higher concentration to a region of lower
concentration.
6
8. 10.1 Diffusion and Osmosis
Factors Affecting the Rate of Diffusion
Factor Effect
Temperature ↑ Temperature, ↑ rate of diffusion
Molecular Mass ↓ Molecular mass, ↑ rate of
diffusion
Thickness of
barrier
↑ (Thicker) cell wall, ↓ rate of
diffusion
Concentration
gradient
↑ Concentration gradient, ↑ rate
of diffusion
Surface-area-to-
volume ratio
↑ Surface area-to-volume ratio, ↑
rate of diffusion
9. 10.1 Diffusion and Osmosis
Surface area-to- volume ratio
Cube Sides 1 cm Sides 2 cm Sides 3 cm
Surface
area/ cm2
6 x 1 x 1 = 6 6 x 2 x 2 = 24 6 x 3 x 3 = 54
Volume/
cm3
1 8 27
Surface
area-to-
volume
ratio
6 : 1 24 :8
= 3 :1
54 : 27
= 2:1
Time/ s 1 3 10
The greater the ratio, the faster the rate of diffusion.
10. Diffusion through a Membrane
Diffusion can also occur
through a membrane.
There are two types of
membranes:
Fully permeable membrane
Example: Cell wall of plant cells
Partially permeable membrane
Example: Cell membrane of cells
10
11. Diffusion through a Permeable Membrane
A fully permeable membrane allows all molecules to
pass through it.
A partially permeable membrane allows only small
molecules but not large molecules to pass through it.
11
12. Diffusion through a Partially Permeable Membrane
A partially permeable membrane allows only small molecules
to pass through its pores but not the large ones.
The small glucose molecules diffuse through the membrane
(Visking tubing) from inside the tube (higher glucose
concentration) into the water (lower glucose concentration).
The starch molecules are too large to pass through the
membrane.
12
13. Diffusion in Living Organisms
1. Photosynthesis
Carbon dioxide diffuses from the air (higher carbon dioxide
concentration) into the cells in the leaves (lower carbon dioxide
concentration)
Oxygen produced diffuses from the cells in the leaves (higher
oxygen concentration) into the air (lower oxygen concentration).
Gases exchange take place via the stomata.
14. Diffusion in Living Organisms
2. The Human Body
In the human digestive system, digested food diffuses
through the wall of the small intestine into the
bloodstream.
Also, food and oxygen diffuse from the blood through
the cell membranes into the body cells.
15. Osmosis
When a piece of raisin is soaked in water, it swells
up and becomes less wrinkled.
Water has diffused into the cells of the raisin through
the partially permeable membrane.
After
soaking in
water for 1 h
Turgid
(larger and firm)
Flaccid
(smaller and soft)
15
16. Osmosis
Osmosis is the net movement of water molecules through
a partially permeable membrane from a region with a
higher concentration of water molecules to a region with
a lower concentration of water molecules.
16
17. An Example of Osmosis
A piece of potato is placed in distilled water.
After 20 minutes
After 20
minutes
original
Distilled water
18. An Example of Osmosis
After 20 minutes of soaking in distilled water, the
potato pieces become larger, longer and firmer.
The water concentration of distilled water is higher
than the water concentration of in the potato cells.
Therefore water molecules move via osmosis from
the distilled water into the potato cells causing them
to swell and become turgid.
19. Another Example of Osmosis
We can show osmosis using Visking tubing.
The pores in the Visking tubing allow the smaller
water molecules but not the larger sugar molecules
to pass through.
20. Another Example of Osmosis
The water concentration is _________ in the
beaker than in the Visking tubing.
Therefore, water molecules move via _________
from the water in the beaker into the Visking
tubing.
higher
osmosis
21. Another Example of Osmosis
This causes the water level in the glass tube to
_______ and the water level in the beaker to
_______.
rise
drop
22. Osmosis in Living Organisms
1. Roots
Water from the soil enters the root hair cells of a
plant by osmosis.
This is because the water concentration in the soil is
higher than in the cell solution of the root hair cells.
23. Osmosis in Living Organisms
2. Stems and Leaves
Water moves into the cells of stems and leaves of a
plant by osmosis.
This makes them firm and strong.
Stems of non-woody plants need turgid cells to support
the plants. If this support is lost, the plant wilts.
24. 24
Why is a transport
system important to
multicellular
organisms?
25. Diffusion and Osmosis in Unicellular
Organisms
In unicellular organisms, materials move into and out
of the cell directly by diffusion and osmosis.
Hence, these organisms do not need a transport
system.
25
O2
CO2
26. Is diffusion and osmosis efficient for
multicellular organisms?
In multicellular organisms, there are many cells. Most of
these cells are far away from the outside of the organism.
Diffusion and osmosis alone are not fast or efficient
enough for the cells to get materials directly from the
environment.
Hence, transport systems are needed to take
substances to all the cells and to carry waste substances
away.
26
28. Checkpoint Time
Diffusion and osmosis are two common modes of
movement for substances in living organisms.
a) Give one example of diffusion taking place in living
organisms.
b) Give one example of osmosis taking place in living
organisms.
28
29. Checkpoint Time
State whether each of the following statements about
osmosis is true or false.
29
Statement True or
False
(a)
Osmosis takes place when two solutions of
different concentrations are separated by a
partially permeable membrane.
(b)
Osmosis can only take place in living tissues.
(c)
Osmosis is the net movement of water molecules
from a solution of lower concentration to a solution
of higher water concentration through a partially
permeable membrane.
31. Learning Outcomes for Section 2
At the end of this lesson, you should be able to:
describe briefly the process of absorption of water and
mineral salts by the root of a plant
describe briefly the transport of water and
manufactured food substances in the plant
explain the function of phloem and xylem
use terms such as translocation, transpiration pull,
active transport, diffusion and osmosis in the
description of plants transport system
31
32. The Tallest Tree in the World
The giant redwood trees
in the USA.
The trees are more than
a 100m tall.
Everyday, the giant
redwood tree moves
1000kg of water from
the soil to their leaves,
100m above the ground.
33. Transport System in Plants
Plants need a transport
system to carry water,
food and dissolved
minerals to all cells in
the plant.
The transport system is
made up of vessels in
the root, stem and
leaves.
34. Vessels of the Plant Transport System
There are two types of
vessels:
1. Xylem Vessels
Made up of dead cells
and have thick walls
Carry water and
dissolved minerals
from the roots to all
parts of the plant.
Xylem vessels
in the roots
35. Vessels of the Plant Transport System
2. Phloem Vessels
Made up of living cells and have thin walls
Carry sugar produced in the leaves to other
parts of the plant.
Phloem vessels
in the roots
36. Vascular Bundles
The two vessels often run side by side forming
vascular bundles.
Xylem vessels in
stem
Phloem vessels in
stem
Vascular bundle
39. 1. Place a balsam plant in a
container of dilute red ink for
one day.
10.3 Transport System in Plants
• Experiment 1: The path of water through a
plant
2. After one day, wash the
roots under running tap
water.
How is water
transported
in a plant?
Transport tissue in plants
40. 3. Observe the stem and leaves of the
balsam plant. You will find that
the red ink has risen in certain
strands of the stem and veins of
the leaf.
10.2 Transport System in Plants
• Experiment 1: The path of water through
a plant
• The strands are vascular bundles which
are part of the plant transport system.
• In the balsam plant, the vascular bundles
are arranged in a ring within the stem.
• Each vascular bundle consists of xylem
tissue and phloem tissue.
Which part of the
vascular bundle
was actually
stained red?
41. 10.2 Transport System in Plants
The xylem tissue
In Experiment 1, the xylem tissue was stained
red. The xylem tissue consists of long tubes or
vessels that pass from the roots to the leaves.
Hence, the xylem tissue is able to transport
water and mineral salts from the roots to the
leaves.
xylem tissue phloem tissue
The phloem tissue
The phloem tissue transports food (e.g.
sugars) produced in the leaves to other parts of
the plant.
42. 10.3 Transport System in Plants
• Experiment 2: How is food transported in
a plant?
1. Take the stem of a woody plant (e.g.
hibiscus). Remove a ring of bark around
the main stem. This should remove the
phloem tissue, leaving the xylem tissue
intact.
2. Water and mineral salts can still be
transported in the plant.
43. 10.3 Transport System in Plants3. After a few weeks, the part of the
stem just above the cut region will
swell.
• Food cannot reach the roots because the phloem
tissue is removed. It collects in the stem just above
the cut, causing that area to swell.
• Without food (sucrose, amino acids), the roots will
starve and die. The plant will eventually die as its roots
cannot take in water from the soil.
What
causes the
swelling at
this part?
45. vacuole
root hair
cell
cytoplasm
cellulose
cell wall
cell
membrane
soil particle
film of water
Soil contains water and mineral
salts. The root hair cells take in
water by osmosis. The root hair
cells also take in mineral salts by
active transport, a process
which requires energy.
Key:
Movement of
mineral salts
Movement of
water molecules
lower concentration of water molecules
higher concentration of water
molecules
Absorption of Water and Mineral Salts by Roots
46. Absorption of Water and Mineral Salts by Roots
Key:
Movement of
mineral salts
Movement of
water molecules
vacuole
root hair
cell
cytoplasm
cellulose
cell wall
cell
membrane
soil particle
film of water
lower concentration of water molecules
higher concentration of water molecules
After the water and mineral salts are
taken in, the water molecules move from
one cell to the next by osmosis.
The mineral salts move
from one cell to the next
by diffusion.
The water and mineral salts will continue to move from one cell to
the next until they reach the stem.
47. Transport of Water and Mineral Salts (Xylem)
Water and mineral salts
move up the plant mainly by
transpiration pull and in
some plants, by root
pressure.
Transpiration pull
This pulling force is produced
when water evaporates from
the leaves through the
stomata.
This force is similar to
someone sucking up liquid
through a straw.
49. Transport of Food (Phloem)
During photosynthesis, food
is produced in the leaves in the
form of sugar (glucose) which
is then transported to other
parts of the plant via the
phloem.
There is a higher sugar
concentration in the leaf than
in the phloem vessels which
are constantly transporting
sugar to other parts of the
plant.
50. Therefore diffusion
occurs to transport
sugar from the leaves
to phloem vessels.
The movement of
glucose in the phloem
occurs in both directions.
Transport of Food (Phloem)
51. Exchanges of Gases during Photosynthesis
Carbon dioxide is needed for
photosynthesis. There is a higher
concentration of carbon dioxide in
the surroundings than in the leaf.
Therefore, carbon dioxide diffuses
from the surroundings to the leaf.
Oxygen is produced during
photosynthesis. There is a higher
concentration of oxygen in the leaf
than in the surroundings. Therefore,
oxygen diffuses from the leaf to the
surroundings.
51
52. Transport System in a Flowering Plant
1. Water enters a plant through its
roots by osmosis. Dissolved minerals
are absorbed through diffusion and
active transport.
2. Water and minerals move up the
stem through xylem vessels.
3. Xylem vessels carry water and
dissolved minerals from the roots to
the leaves.
4. Most of the water evaporates and
diffuses from the leaves through
transpiration.
7. Oxygen diffuses from the leaves to the
surroundings.
8. Sugar moves from the leaves through
phloem vessels to the rest of the plants.
52
Movement of water
Movement of sugar
Movement of carbon dioxide
Movement of oxygen
5. Carbon dioxide diffuses from the
surrounding to the leaves.
6. Carbon dioxide and some water are
used during photosynthesis by the
leaves to produce sugar and oxygen.
53. Checkpoint Time
Complete the following sentences.
1. Water molecules that are taken into a plant move
from one cell to another by ________________.
2. Plants can obtain ______________ and
________________________ from soil.
3. Mineral salts that are taken into a plant move from
one cell to another by __________________.
53
54. Checkpoint Time
The figure below shows a cross section of the stem of
a green plant.
a) Identify the parts labelled 1 and 2.
1: _____________________
2: _____________________
54
55. Checkpoint Time
b) Name the substances transported by the parts
labelled 1 and 2.
1: ______________________________________
2: ______________________________________
55
57. Learning Outcomes for Section 3
At the end of this lesson, you should be able to:
describe and explain the functions of the 3 main
transport system in humans i.e. the heart, the blood
vessels and the blood
understand parts of the heart and the double
circulation system involved
understand the function of arteries, veins and
capillaries and briefly describe areas where they are
found
briefly describe different parts of the blood and how
blood acts as a transport medium
57
58. Transport System in Human
Circulatory system is the main
transport system in the human
body.
It consists of three parts:
1. Heart – an organ which pumps
blood around the body
2. Blood – a liquid which
transport materials
3. Blood vessels – network of
tubes which carry blood round
the body
58
59. Transport System in Human
1. Heart
Its purpose is to pump blood
round the body.
The heart has 4 chambers.
Two upper chambers called the
right atrium and left atrium
(plural: atria)
Two lower chambers called the
right ventricle and left ventricle
(plural: ventricles)
The wall down the middle of the
heart that separates the left side
from the right side is called the
septum.
59
60. Transport System in Human
1. Heart
The valves in the heart open
and close to ensure that blood
flows only in one direction.
60
61. Section of a Mammalian Heart
61
Artery
Septum
Vein
Right atrium
Valve
.
Valve
Right ventricle
Artery
Vein
Left atrium
Valve
.
Valve
Septum
Left ventricle
62. Transport System in Human
2. Blood
The human body has about 5 litres of blood.
Blood has 2 functions:
To transport materials (e.g. nutrients, oxygen, carbon
dioxide and other waste substances) round the body
To protect us against diseases
Blood contains:
a. red blood cells
b. white blood cells
c. platelets
d. plasma
62
63. Transport System in Human
2. Blood
Red blood cells
Red blood cells are biconcave in shape to
increase its surface-area-to-volume ratio for oxygen
absorption.
Red blood cells have no nuclei so as to pack in more
oxygen.
Red blood cells contain haemoglobin, which combines with
oxygen and carries it round the body
The haemoglobin then releases oxygen as it passes the
cells. This oxygen is used by the cells for respiration.
The red blood cells then collect carbon dioxide (a waste
product of respiration) by diffusion.
The red blood cells are bright red when they carry oxygen.
63
64. Transport System in Human
2. Blood
Red blood cells
When oxygen is bound to
haemoglobin, blood appears to
be bright red.
At the cells where oxygen is
needed for respiration,
haemoglobin will release the
oxygen molecules it is carrying.
When oxygen is released from
haemoglobin, blood appears to
be dark red.
The red blood cells then collect
carbon dioxide (a waste product
of respiration) by diffusion. 64
65. Transport System in Human
2. Blood
White blood cells
There are fewer white blood cells than red blood cells.
They are colourless and are larger than red blood cells
and have nuclei.
Some white blood cells are used to fight infections.
They produce antibodies to kill bacteria
Alternatively, they engulf and digest bacteria.
65
67. Transport System in Human
2. Blood
Platelets
These are tiny pieces of blood cells.
They help blood to clot when we bleed.
Platelet
67
68. Transport System in Human
2. Blood
Plasma
Plasma is a pale yellow liquid made up of 95% water with
dissolved substances including nutrients (glucose, amino
acids, fatty acids, mineral salts) and waste substances.
It transports digested food, waste materials (e.g. carbon
dioxide and urea) and other materials (e.g. hormones and
mineral salts).
68
69. Transport System in Human
3. Blood Vessels
Blood vessel is a network of tubes carrying blood
around our body, from the heart to the rest of our body,
and then back to the heart.
There are three types of blood vessels: arteries, veins
and capillaries.
69
70. 3. Blood Vessels
Transport System in Human
Artery Vein Capillary
Function Carry oxygenated blood
away from the heart to all
other parts of the body
Except pulmonary artery
Carry deoxygenated blood
from the rest of the body
back to the heart
Except pulmonary vein
Connect arteries to veins
Carry blood to all cells
Allow exchange of nutrients,
gases and wastes
Pressure Under high pressure Under low pressure -
Thickness of
walls
Have thick, elastic
muscular walls
Have very thin walls Have walls which are one-cell
thick (to ensure fast diffusion of
substances)
Presence of
valves
No Yes (To prevent the
backflow of blood)
No
Diagram
70
71. Transport System in Humans
right
lung
Key:
Deoxygenated blood
Oxygenated blood brain
other parts of
the body
left
lung
Veins
Veins carry blood
towards the
heart.
heart
72. right
lung
Key:
Deoxygenated blood
Oxygenated blood brain
other parts of
the body
left
lung
The arteries
The arteries
carry blood away
from the heart.
The heart
The heart is a muscular
pump. Its pumping action
keeps the blood circulating
around the body quickly and
continuously.
heart
Transport System in Humans
73. n Humans
right
lung
Key:
Deoxygenated blood
Oxygenated blood brain
other parts of
the body
left
lung
The capillaries
These are very tiny blood vessels that
connect the arteries to the veins.
The capillary walls are one-cell thick.
This allows quick diffusion of
nutrients and oxygen from the blood to
the tissue cells.
The capillaries
Waste substances such as carbon dioxide
can also move from the tissue cells into the
blood in the capillaries.
Blood
Blood is continuously
circulated around the body,
transporting many substances.
Blood also protects the body
from disease-causing germs.
Blood
In places with low oxygen, our
body produces more red blood
cells to transport more oxygen.
heart
Transport System in Humans
75. Transport System in Human
Explain why the left ventricle has a thicker muscular
wall than the right ventricle.
75
The left ventricle must
pump blood at high
pressure so that blood
can travel to the rest
of the body.
76. Double Circulation in Human
The double circulatory system of blood flow occurs when
the blood enters the heart twice.
All animals with lungs have a double circulatory system.
The cycle is heart body heart lungs heart
In contrast, fish have a single circulation system because
they do not have lungs.
The cycle is heart gills body heart
76
77. Double Circulation in Human
Double circulation is much more efficient than single
circulation. In a fish blood pressure goes down as is
passes through capillaries in gills so it is slower and
takes longer for oxygen and nutrients to get around the
body.
In humans the blood pressure can be increased after it
has left the lungs. It is faster. Humans are more active
than fish and need to produce more energy and heat.
77
78. Respiratory System: Lungs
In the lungs, blood picks up oxygen and loses
carbon dioxide.
The air we breathe contains high concentration of
oxygen and low concentration of carbon dioxide.
Lung
79. The blood flowing towards the lungs contains low
concentration of oxygen and high concentration of
carbon dioxide.
Therefore, oxygen from the lungs will diffuse into the
blood and carbon dioxide from the blood will diffuse
into the lungs.
Respiratory System: Lungs
Lung
81. Digestive System
In the small intestine,
blood picks up small,
digested food molecules
such as glucose, amino
acids and fatty acids.
As the blood flows around
the body, it will distribute
these food molecules to
the cells that need them.
Oesophagus
83. Checkpoint Time
The diagram below shows a vertical section of the
heart in humans.
Label A, B, C and D.
A: __________________ B: ___________________
C: __________________ D: ___________________
83
84. Checkpoint Time
The diagram below shows a vertical section of the
heart in humans.
In which labelled structure does blood reach the
maximum pressure?
84
