1 2 think about… 3.1 cell membrane 3.2 movement of substances across membranes recall ‘think...
TRANSCRIPT
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2
Think about…
3.1 Cell membrane
3.2 Movement of substances across membranes
Recall ‘Think about…’
Summary concept map
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Let me show you how to make it!
spring onion flower
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Cut several vertical slits at one end.
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Place it in water for 1 minute.
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Cut tips curl outwards like a flower!
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Why do the cuttips of spring onion curl outwards after placing in water
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The cut tips will curl inwards if the spring onion is put in sucrose solution.
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Why
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3.1 Cell membrane
cell membrane
10
outside cell
inside cell
cell membrane
• separates the cell contents from the outside environment
3.1 Cell membrane
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outside cell
inside cell
3.1 Cell membrane
• control the movement of substances into and out of cells
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What is the structure of the cell membrane?
3.1 Cell membrane
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3.1 Cell membrane
Structure of cell membrane
fluid mosaic model (流動鑲嵌模型 )
• explained by
3D Model
14
phospholipid bilayer (磷脂雙層 )
3.1 Cell membrane
protein molecules
Fluid mosaic model
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Phospholipids
lipid molecule =
1 glycerol molecule
+
3 fatty acid molecules
3.1 Cell membrane
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phospholipid molecule:
1 fatty acid molecule
phosphate group
3.1 Cell membrane
Phospholipids
replaced by
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3.1 Cell membrane
water-loving ‘head’
Phospholipids
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3.1 Cell membrane
water-repelling ‘tail’
Phospholipids
19
3.1 Cell membrane
inside cell
outside cell
phospholipid bilayer
Phospholipids
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3.1 Cell membrane
inside cell
outside cell
phospholipid molecules arranged tail-to-tail
Phospholipids
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3.1 Cell membrane
inside cell
outside cell
water-loving ‘heads’ face water-based environment
Phospholipids
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3.1 Cell membrane
protein molecules
Fluid mosaic model
phospholipid bilayer (磷脂雙層 )
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Proteins3.1 Cell membrane
embed half-way through bilayer
penetrate through bilayer
• protein arrangement:
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Proteins3.1 Cell membrane
What are their functions?
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i) Act as channels
3.1 Cell membrane
water soluble substances
ions
Proteins
ions water soluble substances
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3.1 Cell membrane
active transport
Proteinsii) Act as carriers
energy
27
3.1 Cell membrane
Proteinsiii) Act as chemical receptors
turn on cell
activities
hormones
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3.1 Cell membrane
Proteins
enzymesiv) Act as enzymes
speed up reactions
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different among cells
3.1 Cell membrane
Proteins
carbohydrate molecule
v) For recognition (識別 )glycoprotein( 糖蛋白 )
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3.1 Cell membraneCell membrane
Why called fluid mosaic model?
Fluid mosaic model
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phospholipid bilayer
some protein molecules
can move laterally
Fluid mosaic model
3.1 Cell membraneCell membrane
32interspersed in a mosaic pattern
3.1 Cell membrane
protein molecules
Fluid mosaic model
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3.1 Cell membrane
Fluid mosaic model
How can the model explain these properties
and function?
• cell membrane- differentially permeable- flexible- supports the cell contents
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1 Differential permeability
inside cell
outside cell
• lipid-soluble substances, simple and small molecules:
inside phospholipid bilayer:
water-repelling / fat-loving
through bilayer
3.1 Cell membrane
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3.1 Cell membrane
1 Differential permeability
inside cell
outside cell
• water molecules, certain ions, water-soluble substances:
phospholipid bilayer:
impermeable to them
through channel proteins or
carrier proteins
36
3.1 Cell membrane
1 Differential permeability
inside cell
outside cell
• large molecules:
cannot pass through
37
3.1 Cell membrane
fluid nature of phospholipid bilayer
2 Flexibility
membrane can change shape or seal itself
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3.1 Cell membrane
fluid nature of phospholipid bilayer
2 Flexibility
membrane can change shape or seal itself
cell division
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3.1 Cell membrane
3 Supporting role• interspersed protein molecules give
strength
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3.1 Cell membrane
3 Supporting role• interspersed protein molecules give
strength
support cell contents
41
3.1 Cell membrane
What is the membrane structure according to the fluid mosaic model?
How is it related to its properties and functions?
42
Structure Properties & functions
-
bilayer
- act
as channels
or carriers
- Cell membrane is
3.1 Cell membrane
Proteinsdifferentially permeable
Phospholipid
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Structure Properties & functions
- Proteins are
in bilayer
- Cell membrane is
strong enough to
cell contents
3.1 Cell membrane
interspersed
support
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Structure Properties & functions
- in
nature
- Cell membrane is
so that it can
change its shape and
seal itself
3.1 Cell membrane
Fluid
flexible
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diffusion 1
active transport 3
osmosis2
phagocytosis4
diffusion 1
3.2 Movement of substances across membrane
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• all substances are made up of particles
Diffusion (擴散 )
cannot move from one place to another
can move more freely
liquid gassolid
3.2 Movement of substances across membrane
3D Animation
47
In liquid or gas
• no concentration gradient• particles move randomly in all directions
3.2 Movement of substances across membrane
Diffusion (擴散 )
no difference in concentration
48
In liquid or gas
3.2 Movement of substances across membrane
Diffusion (擴散 )
• concentration gradient exists
higher concentration
lowerconcentration
49
In liquid or gas
3.2 Movement of substances across membrane
Diffusion (擴散 )
• net movement of particles from higher to lower concentration
net movement
until evenly distributed
50
In liquid or gas
3.2 Movement of substances across membrane
Diffusion (擴散 )
• no energy is required
net movement
until evenly distributed
• passive process
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Factors affecting the rate of diffusioni) Difference in concentration
steeper less steep
higher rate lower rate
3.2 Movement of substances across membrane
Diffusion (擴散 )
concentration gradient
52
higher temperature
lower temperature
3.2 Movement of substances across membrane
Diffusion (擴散 )Factors affecting the rate of diffusionii) Temperature
higher rate lower rate
53
3.2 Movement of substances across membrane
Diffusion (擴散 )Factors affecting the rate of diffusioniii) Size and nature of particles
larger smaller
higher ratelower rate
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3.2 Movement of substances across membrane
Diffusion (擴散 )Factors affecting the rate of diffusioniii) Size and nature of particles
water-soluble lipid-soluble
higher ratelower rate
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1 Transport of substances
Importance
oxygen
small & lipid-soluble nutrients
wastesimple ions
2 Distribution of substances
3.2 Movement of substances across membrane
Diffusion (擴散 )
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diffusion 1
active transport 3
osmosis2
phagocytosis4
3.2 Movement of substances across membrane
osmosis2
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• diffusion of water molecules across a differentially permeable membrane
Osmosis (滲透 )3.2 Movement of substances across membrane
Let me explain in terms of water potential (水勢 )
3D Animation
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Water potential Ψ• describe tendency of water molecules
to move from one place to the other
3.2 Movement of substances across membrane
Osmosis (滲透 )
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water molecule
Ψ = 0 Ψ = negative
solute
3.2 Movement of substances across membrane
Osmosis (滲透 )Water potential Ψ
Pure water Solution
• solutes lower the water potential
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Pure water Solution
solute
3.2 Movement of substances across membrane
Osmosis (滲透 )
• solutes lower the water potential
Ψ = 0 Ψ = negative
Water potential Ψ
water molecule
The higher the concentration of a solution, the lower
its water potential.
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3.2 Movement of substances across membrane
Osmosis (滲透 )
differentially permeable membrane
Water potential ΨPure water Solution
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3.2 Movement of substances across membrane
Osmosis (滲透 )
solutes are too large to
pass through
Water potential ΨPure water Solution
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3.2 Movement of substances across membrane
Osmosis (滲透 )
water molecules can pass through
Water potential ΨPure water Solution
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3.2 Movement of substances across membrane
Osmosis (滲透 )
more water molecules
move to the right
higher Ψ lower Ψ
Water potential ΨPure water Solution
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3.2 Movement of substances across membrane
Osmosis (滲透 )
net movement
higher Ψ lower Ψ
Water potential ΨPure water Solution
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• diffusion of water molecules across a differentially permeable membrane
Osmosis (滲透 )3.2 Movement of substances across membrane
net movement of water molecules from a region of higher water potential to a region of lower
water potential
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3.1
3.2 Movement of substances across membrane
Demonstration of osmosis using dialysis tubing
1 Wet a dialysis tubing with tap water. Tie a knot at one end.
2 Fill the tubing with 20% sucrose solution.
3 Tie the other end to a capillary tube. Rinse with distilled water.
Video
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3.1
4 Immerse the tubing in water.
liquid level
Mark the initial liquid level.
3.2 Movement of substances across membrane
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3.1
5 Set up a control by filling another tubing with distilled water instead of sucrose solution.
distilled water
3.2 Movement of substances across membrane
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3.1
6 Note any changes in the liquid levels after 30 minutes.
experimental set-up
control set-up
3.2 Movement of substances across membrane
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3.1
Results and discussion
• The liquid level in the experimental set-up rises. • The liquid level in the control set-up falls until it reaches the liquid
level of the water in the beaker.
3.2 Movement of substances across membrane
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3.1
Results and discussion
• When sucrose solution is separated from distilled water by the differentially permeable dialysis tubing,
3.2 Movement of substances across membrane
there is a net movement of water molecules from distilled water to the sucrose solution.
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1 Cover the mouth of a thistle funnel with a piece of living animal tissue. Tie the tissue tightly with a thread.
3.2
3.2 Movement of substances across membrane
Demonstration of osmosis using living animal tissue
2 Invert the funnel and fill it with concentrated sucrose solution.
Video
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3.2
3 Immerse the funnel in a beaker of water. (Set-up A). Mark the initial liquid level.
distilled water
concentrated sucrosesolution
animal tissue
liquid level
3.2 Movement of substances across membrane
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3.2
4 Prepare a similar set-up (set-up B) by filling the thistle funnel with distilled water instead of sucrose solution.
distilled water
3.2 Movement of substances across membrane
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3.2
5 Observe any changes in the liquid levels after 30 minutes.
set-up A set-up B
3.2 Movement of substances across membrane
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3.2
Results and discussion• In set-up A, the liquid level rises.
Distilled water has a higher water potential than concentrated sucrose solution.
There is a net movement of water molecules from the outside into the thistle funnel through the differentially permeable animal tissue by osmosis.
3.2 Movement of substances across membrane
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3.2
Results and discussion• In set-up B, the liquid level gradually falls.
It serves as a control. When the liquid levels in the thistle funnel and the
beaker become the same, no osmosis takes place.
3.2 Movement of substances across membrane
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plant cells
animal cells
• gain or lose water by osmosis,depending on the surrounding solution
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
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solution with Ψ higher than cytoplasm
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
In hypotonic (低滲的 ) solutio
n
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animal cell
higher Ψlower Ψwater entersby osmosiscontinuously
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
cell swellscell finally bursts
In hypotonic (低滲的 ) solutio
n
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animal cell
cell swellscell finally bursts
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
In hypotonic (低滲的 ) solutio
n
83
plant cell water enters by osmosis
3.2 Movement of substances across membrane
Osmosis (滲透 )
lower Ψ higher Ψ
Cells and osmosis
In hypotonic (低滲的 ) solutio
n
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plant cell restricted by rigid cell wall, water stops entering
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
In hypotonic (低滲的 ) solutio
n
85
plant cell
cell finally becomes turgid (膨脹 )
In hypotonic (低滲的 ) solutio
n
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
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solution with Ψ lower than cytoplasm
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
In hypertonic (高滲的 ) solutio
n
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water leavesby osmosis
In hypertonic (高滲的 ) solutio
n
3.2 Movement of substances across membrane
Osmosis (滲透 )
lower Ψhigher Ψanimal
cell
Cells and osmosis
cell shrinks (萎縮 ) & becomes wrinkled (皺褶 )
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In hypertonic (高滲的 ) solutio
n
3.2 Movement of substances across membrane
Osmosis (滲透 )
animal cell
Cells and osmosis
cell shrinks (萎縮 ) & becomes wrinkled (皺褶 )
89
water leavesby osmosis
3.2 Movement of substances across membrane
Osmosis (滲透 )
lower Ψhigher Ψplant cell
Cells and osmosis
In hypertonic (高滲的 ) solutio
n
plasmolysis (質壁分離 ) occurs & cell becomes flaccid (軟縮 )
90
3.2 Movement of substances across membrane
Osmosis (滲透 )
plant cell
Cells and osmosis
In hypertonic (高滲的 ) solutio
n
plasmolysis (質壁分離 ) occurs & cell becomes flaccid (軟縮 )
91
In isotonic (等滲的 ) solutio
n
solution with Ψ same as cytoplasm
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
92animal cell plant cell
cell volume remains the same
no net water
movement
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
In isotonic (等滲的 ) solutio
n
93
When a cell is put in an isotonic solution, there is no water movement across its membrane.
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
94
Water moves into and out of the cell across the cell membrane all the time, but with no NET water movement across the membrane.
3.2 Movement of substances across membrane
Osmosis (滲透 )Cells and osmosis
95
• for entry and exit of water into and out of the cells
animal cell plant cell
3.2 Movement of substances across membrane
Osmosis (滲透 )Importance
96
3.2 Movement of substances across membrane
Osmosis (滲透 )Importance• for movement of water from one cell
to another in plants
H2O
97
• for transporting water through living tissues
3.2 Movement of substances across membrane
Osmosis (滲透 )Importance
bloodH2O H2O
98
Study of osmosis in red blood cells1 Examine prepared slides of red blood cells
in different concentration of NaCl solutions under the microscope.
red blood cells
3.3
3.2 Movement of substances across membrane
99
2 Note the appearance of red blood cells. Suggest which concentration of NaCl solution is hypertonic, hypotonic and isotonic to the cells.
3.3
3.2 Movement of substances across membrane
100
3.3Red blood cells in NaCl solutions (×400)
3.2 Movement of substances across membrane
0% 0.45%
1.35% 1.8%
0.9%
101
3.3
Results and discussion
In 0.9% NaCl solution
3.2 Movement of substances across membrane
• red blood cells appear normal
isotonic
0.9%
102
3.3
Results and discussion
In 0% and 0.45% NaCl solution
0% 0.45%
• red blood cells swell
hypotonic
3.2 Movement of substances across membrane
103
3.3
Results and discussion
In 1.35% and 1.8% NaCl solution
1.35% 1.8%
• red blood cells shrink and become wrinkled
hypertonic
3.2 Movement of substances across membrane
104
Study of osmosis in living plant cells
3.4
1 Peel off the epidermis of a Zebrina (水竹草 ) leaf. Cut a small piece and lay it flat on a slide.
3.2 Movement of substances across membrane
Video
105
3.4
2 Add a drop of concentrated sucrose solution and put a cover slip over the epidermis.
Wait for 3 minutes.
3 Observe the epidermis under a microscope.
3.2 Movement of substances across membrane
106
3.4
4 Slowly replace the concentrated sucrose solution with distilled water. Observe with a microscope.
add distilled water slowly
draw distilled water slowly by tissue paper
3.2 Movement of substances across membrane
107
3.4
Results and discussion
Zebrina epidermal cells (×100)
In concentrated sucrose solution• cells lose water by
osmosis and become plasmolysed
3.2 Movement of substances across membrane
108
3.4
Results and discussion
Zebrina epidermal cells (×100)
In distilled water• cells gain water by
osmosis and become turgid
3.2 Movement of substances across membrane
109
3.4
• plasmolysis is usually reversibleResults and discussion
plasmolysed turgid
3.2 Movement of substances across membrane
110
1 Add distilled water, 10% and 20% sucrose solution into 3 beakers respectively.
Study of osmosis in living plant tissue
3.5
3.2 Movement of substances across membrane
Video
111
3.5
2 Use a cork borer to make 9 strips from a potato. Cut each of them to 5 cm long.
potato
cork borer
3.2 Movement of substances across membrane
112
3 Blot the potato strips with tissue paper. Weigh the strips with an electronic balance.
Record the initial weight.
potato strip
3.5
3.2 Movement of substances across membrane
113
3.5
4 Put 3 potato strips into each beaker. Cover the beakers and leave them for 1 hour.
distilled water
10% sucrose solution
20% sucrose solution
plastic food wrap
3.2 Movement of substances across membrane
114
3.5
5 Remove the potato strips and blot them with tissue paper. Weigh the strips immediately. Record the final weight of the strips.
6 Calculate the average values of the percentage change in the weights of the strips in each beaker.
3.2 Movement of substances across membrane
115
3.5
• potato strips become heavier
net movement of water into the cells by osmosis
distilled water is hypotonic to potato tissue
Results and discussion
In distilled water
3.2 Movement of substances across membrane
116
3.5
• weight changes slightly
10% sucrose solution is nearly isotonic to potato tissue
Results and discussion
In 10% sucrose solution
10%
3.2 Movement of substances across membrane
117
3.5
• potato strips become lighter
net movement of water out of the cells by osmosis
20% sucrose solution is hypertonic to potato tissue
Results and discussion
In 20% sucrose solution
20%
3.2 Movement of substances across membrane
118
diffusion 1
active transport 3
osmosis2
phagocytosis4
3.2 Movement of substances across membrane
active transport 3
119
Active transport (主動轉運 )
higher concentration
lowerconcentration
Can move against concentration gradient using
ENERGY!
3.2 Movement of substances across membrane
3D Animation
120
Active transport (主動轉運 )
net movement
• Usually from lower to higher concentration
3.2 Movement of substances across membrane
121
Active transport (主動轉運 )
net movement
• carried out by carrier proteins in the membrane
3.2 Movement of substances across membrane
122
Active transport (主動轉運 )
• carried out by carrier proteins in the membrane
3.2 Movement of substances across membrane
123
carrier protein
Active transport (主動轉運 )
inside celloutside cell
higher concentration
lower concentration
3.2 Movement of substances across membrane
124
Active transport (主動轉運 )
lower concentration
higher concentration
3.2 Movement of substances across membrane
inside celloutside cell
substances combine with carrier protein
125
Active transport (主動轉運 )
lower concentration
change shape
higher concentration
3.2 Movement of substances across membrane
inside celloutside cell
energy
substances released into cell
126
energy
respiration
• active process• energy obtained from respiration
Active transport (主動轉運 )
mitochondrion
• only in living cells
3.2 Movement of substances across membrane
127
energy
respiration
• no respiration, no active transport
Active transport (主動轉運 )
mitochondrion
lack of oxygencyanide
active
transport
3.2 Movement of substances across membrane
128
• mineral absorptionsoil: lower mineral
concentration
root: higher mineralconcentration
Active transport (主動轉運 )Importance
3.2 Movement of substances across membrane
129
• mineral absorptionsoil: lower mineral
concentration
root: higher mineralconcentration
Active transport (主動轉運 )Importance
against concentration gradient
3.2 Movement of substances across membrane
130
• glucose absorption
villus of small intestine
lumen: higher glucoseconcentration
blood: lower glucoseconcentration
Active transport (主動轉運 )Importance
active transport
3.2 Movement of substances across membrane
131
along concentration
gradient at a higher speed
• glucose absorption
Active transport (主動轉運 )Importance
lumen: higher glucoseconcentration
blood: lower glucoseconcentration
3.2 Movement of substances across membrane
132
diffusion 1
active transport 3
osmosis2
phagocytosis4
3.2 Movement of substances across membrane
phagocytosis4
133
Phagocytosis (吞噬 )
‘eat’
3.2 Movement of substances across membrane
134
‘cell’
Phagocytosis (吞噬 )3.2 Movement of substances across membrane
135
• single-celled organisms and certain white blood cells engulf large particles
• energy is required
• ‘cell-eating’Phagocytosis (吞噬 )
white blood cell
particle
3.2 Movement of substances across membrane
136
digested products
enzyme
Phagocytosis (吞噬 )
inside cell
outside cell
diffuse to cytoplasm
particle
pit
vacuole
• start with infolding of membrane or formation of pseudopodia (偽足 )
3.2 Movement of substances across membrane
Animation
137
• nutrition of some single-celled organisms
Ameobaalga
Phagocytosis (吞噬 )Importance
3.2 Movement of substances across membrane
138
• body defence against diseases
Phagocytosis (吞噬 )Importance
white blood cell
harmful microorganism
3.2 Movement of substances across membrane
139
Examine the process of phagocytosis in Amoeba with a video-imaging device. Note the following:
1 the formation of pseudopodia
2 how the cell engulfs the particle
3 the type of particle the cell engulfs
Examination of phagocytosis in Amoeba
3.6
3.2 Movement of substances across membrane
Video
140
3.6
alga
Amoeba
Amoeba engulfing food particle by phagocytosis (×100)
3.2 Movement of substances across membrane
141
3.6
• The Amoeba start to surround the alga.
3.2 Movement of substances across membrane
142
3.6
• The alga is engulfed by the Amoeba.
3.2 Movement of substances across membrane
143
1 Let’s compare diffusion, osmosis, active transport and pha
gocytosis!!!
3.2 Movement of substances across membrane
144
Net movement of particles:Diffusion Osmosis
From high to low concentration
From high Ψ to low Ψ
Active transport Phagocytosis
Usually from low to high concentration
Into the cell
1a
3.2 Movement of substances across membrane
145
Membrane needed?1bDiffusion Osmosis
No Differentially permeable membrane
Active transport Phagocytosis
Living cell membrane
Living cell membrane
3.2 Movement of substances across membrane
146
Energy needed?1cDiffusion Osmosis
No No
Active transport Phagocytosis
Yes Yes
3.2 Movement of substances across membrane
147
2 What happens to a cell if it is put in a hypotonic, a hypertonic or an isotonic solution respectively?
3.2 Movement of substances across membrane
148
out of the cell
no net movement
into the cell
hypotonic solution
isotonic solution
hypertonic solution
solution surrounding
the cell
net movement of water
3.2 Movement of substances across membrane
149
3 What happens to a cell if it is an animal cell and a plant cell respectively?
3.2 Movement of substances across membrane
150
Hypotonic
solution
Hypertonic
solution
Isotonic
Solution
Animal cell
an
d may
an
d becomes
Remains
in water c
ontent
Swells Shrinks
normal
burst
wrinkled
3.2 Movement of substances across membrane
151
Hypotonic
solution
Hypertonic
solution
Isotonic
solution
Plant cell
Becomes Vacuole
;
occurs;
becomes
Remains
in water c
ontent
plasmolysis
shrinks
flaccid
turgid normal
3.2 Movement of substances across membrane
152
Why do the cut tips of spring onioncurl outwards after placing in water?1
• Water is hypotonic to the cells.
Water enters cells by osmosis.
Cells become turgid & increase in size.
153
• The cells at the outer layer are covered with a waxy layer.
It limits the increase in cell size.
The cells at the inner layer expand more quickly.
154
The cut tips curl outwards
inner layer of cells expand more quickly
outer waxy layer
155
The cut tips will curl inwards if the spring onion is put in sucrose solution.Why?
2
• Sucrose solution is hypertonic to the cells.
Cells lose water and lose turgidity.
156
The cut tips curl inwards.
inner layer of cells lose water and become flaccid more quickly
outer waxy layer
157
its structure can be explained by
Cell membrane
proteinsa phospholipid
bilayer
fluid mosaic modelstates that the cell membrane is made up of
embeddedwith
158
including
channel proteins
carrier proteins
proteins
159
Cell membrane allows substances
to move across it by
osmosis
active transport
phagocytosis
diffusion
160
diffusion
down a concentration gradient
is the net movement of particles
161
osmosis
down a water potential gradient
is the net movement of water molecules
162
active transport
usually against a concentration gradient
is the movement of particles
process requires
energy
163
phagocytosis
pits or pseudopodia
in which
large particles
are engulfed by forming