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BIOLOGY FORM 4 
CHAPTER 3 
MOVEMENT OF SUBSTANCES ACROSS 
THE PLASMA MEMBRANE
SUBTOPICS 
3.1 - Movement of Substances Across the 
Plasma Membrane 
3.2 – Understanding the Movement of 
Substances Acros...
LEARNING OUTCOMES 
• To state the substances required by living cells 
• To state the substances that have to be 
eliminat...
Substances to be eliminate from the cells 
• Water 
• Nutrient 
– Glucose 
– Amino acid 
– Mineral 
– Fatty acid 
– Vitami...
NECESSITY FOR MOVEMENT OF SUBSTANCES 
ACROSS THE PLASMA MEMBRANE 
 To provide nutrients for metabolism & growth; 
 To su...
PLASMA MEMBRANE
Functions of the plasma membrane: 
1. Boundary- barrier to environment. 
Saparates the contents of the cells 
from their e...
The plasma membrane of a cell 
can be thought of as a gatekeeper: 
allowing only specific substances in or out 
passing...
Which term is better to describe a 
plasma membrane? 
semi-permeable 
Only allows certain substances to pass through
The general structure of membranes 
is know as the: fluid mosaic model 
Fluid 
refers to the 
phospholipid 
bilayer 
Mosai...
This model is referred to as the ‘fluid mosaic 
model’ because the components are free to 
move independently of each othe...
The main components of the plasma 
membrane are: 
Protein 
Side view 
Phospholipid 
4.6
Outer & inner membrane 
surfaces differ.
Let us explain how 
a bilayer forms
Structure of a phospholipid 
molecule 
Hydrophilic head 
(phosphate) 
Hydrophobic tail 
(fatty acid) 
What happens when a ...
4.6
4.6
4.6 
They arrange themselves 
into a single layer
4.6 
A spherical 
micelle
Two layers form: a bilayer 
4.6 
phospholipid bilayers like this are the basic 
structure of plasma membranes
Phospholipids can move within the 
membrane 
The phospholipid bilayer is flexible, and the 
interior is fluid, allowing la...
Proteins can move within the Plasma Membrane 
Side view 
Surface view
Let us have a look at 
PROTEINS
PROTEINS 
 There are proteins on the outer & inner surfaces of 
the plasma membrane. 
 Some proteins penetrate partially...
Transport Proteins 
2 types: 
1. Channel/pore proteins are embedded in the cell 
membrane & have a pore for materials to c...
The phospholipid bilayer only allows CERTAIN 
materials to cross. 
polar 
head 
nonpolar 
tails 
hydrophobic 
molecules 
h...
The phospholipid bilayer does not 
polar 
head 
allow all materials to cross 
nonpolar 
tails 
hydrophobic 
molecules 
hyd...
Nonpolar, hydrophobic 
solutes Polar, ionised, 
hydrophilic 
solutes
Charged molecules & ions can 
enter a cell. How can this be? 
Move 
through a 
protein. 
Big & polar 
molecules (glucose, ...
Which substances can/cannot pass 
through the phospholipid bilayer? 
Small 
amounts.
Explain why organic solvents such as 
alcohol, ether and chloroform penetrate 
membranes more readily than water. 
Alcohol...
Recall concept on “Cell 
surface membrane” which is 
found in all living cells 
 Partially-permeable 
membrane that forms...
MOVEMENT THROUGH THE 
PLASMA MEMBRANE
LEARNING OUTCOMES 
 To explain the movement of substances across the 
plasma membrane through the process of passive 
tra...
PASSIVE
PASSIVE TRANSPORT 
ACTIVE TRANSPORT 
Cell uses ATP 
high 
Weeee!!! 
low 
Cell does not use ATP: substances 
just diffuse t...
DIFFUSION 
is the movement of molecules or ions 
from a region of high concentration to 
region of low concentration down ...
Describing the process of DIFFUSION 
Molecules (possess 
kinetic/movement energy) 
moving down a 
concentration gradient 
...
51 
Diffusion of Liquids
Diffusion 
• Water, carbon dioxide and other small 
uncharged particles
The rate of diffusion depends on 
1. The steepness of the 
diffusion gradient 
 the steeper the 
gradient, the faster 
th...
Blood carries away the digested 
food
In windy conditions, air outside 
leaves becomes drier 
Water diffuses faster through the stomata
At a higher temperature the particles have more kinetic 
energy and are moving around faster. Therefore in a given 
time m...
The surface area of the second cell is much bigger than the first cell 
due to the folded membrane. The volume of the cell...
The larger the surface area of a membrane 
through which diffusion is taking place, the faster 
the diffusion
Surface Area 
• As the rate of diffusion relies on the surface 
area. 
• The parts of organisms that rely on diffusion 
th...
Rate of diffusion decreases rapidly with 
distance 
 diffusion is effective over very short 
distances 
Squamous epitheli...
EXAMPLE OF DIFFUSION
Diffusion in lungs 
 The cells of your lungs exchange oxygen and 
carbon dioxide through diffusion.
A single air sac 21 
blood supply to air sac 
air breathed 
in and out 
diffusion of 
oxygen 
diffusion of 
carbon dioxide...
Diffusion in root hair cells 
 Plant cells such as root hair cells also take in 
oxygen and remove carbon dioxide through...
Leaf 
O2 and CO2 diffuse 
into the spaces between cells 
the ‘veins’ 
bring water 
O2 and CO2 
diffuse through 
pores in t...
Diffusion of O2 & water vapour 
through stomata
FACILITATED DIFFUSION
Two types of diffusion 
Simple diffusion: 
small molecules cross 
the lipid bilayer 
Facilitated diffusion: 
substances cr...
Difference between 
channel & carrier proteins: 
Channel proteins 
fixed shape 
Carrier proteins 
undergo rapid changes 
i...
Down or Against a concentration 
gradient? 
Simple & Facilitated 
Diffusion: 
Active 
transport:
Which substances enter by 
facilitated diffusion? 
 those that cannot diffuse through the 
phospholipid bilayer such as: ...
Facilitated diffusion can occur 
through a: 
Non-specific 
transporter 
Specific 
transporter
Carrier proteins: 
 substance to be transported is bound to a 
membrane protein
Why does the rate of uptake reach 
a maximum in facilitated diffusion? 
Carriers are saturated. 
Simple 
diffusion 
Facili...
Facilitated diffusion has three 
essential characteristics: 
 it is: 
1. Specific 
2. Passive 
3. Saturates
85 
Facilitated Diffusion 
Molecules will randomly move through 
the pores in Channel Proteins.
86 
Facilitated Diffusion 
• Some Carrier 
proteins do not 
extend through 
the membrane. 
• They bond and 
drag molecules...
87 
Carrier Proteins 
• Other carrier 
proteins 
change shape 
to move 
materials 
across the cell 
membrane
Define: 
Simple diffusion: 
The passive transport of substances 
across the plasma membrane 
Facilitated diffusion: 
The p...
EXAMPLES OF 
FACILITATED DIFFUSION
OSMOSIS
Osmosis 
 is the passage of water molecules from a 
region of their high concentration to a 
region of their low concentr...
Water continues to flow until: 
equilibrium is 
reached
Three terms are used to compare 
the solute concentrations of two 
solutions separated by a membrane: 
Isotonic 
Hypotonic...
Isotonic solutions 
[same concentration]
Hypotonic 
solution 
Hypertonic 
solution 
[lower conc. of 
solute] 
[higher conc. 
of solute]
Water molecules always move from 
from HYPOTONIC solution to 
HYPERTONIC solution 
HYPO  HYPER
Osmosis 
Partially 
permeable 
membrane 
High Water 
Concentration 
means the 
solution is 
Hypotonic 
Loses water by 
Wat...
ISOTONIC
HYPERTONIC
HYPOTONIC
Osmosis in Animal Cells
isotonic 
solution 
Crenated cells haemolysis 
hypertonic 
solution 
10 microns 
hypotonic 
solution 
equal movement of wa...
Name the solutions 
Osmosis in Red Blood Cells 
Isotonic Hypotonic Hypertonic
Plant cells in a hypotonic solution: 
Water enters the cell and 
fills the vacuole. 
The plasma membrane 
pushes against t...
Plant cells in a hypertonic solution: 
The cell loses water and goes 
FLACCID. 
REASON: 
 the vacuole becomes flaccid 
 ...
HYPOTONIC ISOTONIC HYPERTONIC
Why is it that 
plant cells do 
not burst? 
Presence of a 
cell wall.
115 
hypotonic hypertonic isotonic 
hypertonic isotonic hypotonic
Hypertonic Isotonic Hypotonic 
Plasmolysed Flaccid Turgid 
PLANT 
CELLS
Onion epidermal cells were 
placed in a 1M sucrose solution. 
What fills the space 
between the cell wall 
and the protopl...
(1) wilting 
(2) recovering 
(1) Wilting. Pant is short of water. The leaf 
cells are no longer turgid and the leaves curl...
Importance of Turgor pressure 
• Helps to support the soft tissues of plants so 
that they remain firm. 
• Absence of turg...
Potato strips were first placed in either 
a hypotonic or a hypertonic solution, 
than in water. Why did potato 
strips P ...
Osmosis demo 
• The membrane contains 
strong sugar solution. 
• The membrane is stood 
in a weak sugar solution. 
• Soon ...
Osmosis demo 
• Water molecules can 
diffuse through the 
membrane from the 
weak solution to the 
strong one. 
• Sugar mo...
HYPERTONIC 
HYPOTONIC
Visking tubing 
0.5% 
Sugar 
solution 
0.1% 
Sugar 
solution
Visking tubing 
0.5% 
Sugar 
solution 
0.1% 
Sugar 
solution 
Water moves from a dilute solution to a more concentrated 
o...
Amoeba has a cytoplasm that is 
hypertonic to the pond water in which it 
lives 
What does this lead to? 
Net flow of wate...
What is the role of the 
contractile vacuole? 
Expels excess water from the cell
Amoeba may also adjust the quantity of 
dissolved substances in the cytoplasm 
Amoeba actively pumps out ions. 
How does t...
Why the use of 
excess fertilizer caused 
wilting in plant?
Wilting of Plants 
• Problems can arise if chemical fertilisers 
are added in excess to the soil. 
• The soil solutions be...
Explain these preservation process
Preservation of Food 
• Food can be preserved by using salt or 
sugar. 
• When salt or sugar is added to the food, it 
cre...
ACTIVE TRANSPORT
Active Transport 
Problem: 
• Diffusion is very slow 
• moves substances down a concentration gradient. 
• Many substances...
Active Transport 
Active transport occurs using channel proteins.
Movement of substances by active 
transport is usually in 
one direction only. 
What about in 
diffusion? 
Direction is re...
ATP supplies the energy for active 
transport. What is the use of energy? 
The carrier proteins need energy to 
keep chang...
EXAMPLES OF 
ACTIVE TRANSPORT
168 
Sodium-Potassium Pump 
in plasma membrane of neurones 
3 Na+ pumped in for every 2 K+ pumped 
out; creates a membrane...
Active transport in small 
intestine
Active transport in root hair 
cells
LEARNING OUTCOMES 
• To explain the process of active transport in 
living organisms using examples, 
• To compare and con...
Remember the Examples 
 Examples of diffusion: 
= gaseous exchange between the alveolus & the blood 
capillaries, blood c...
MOVEMENT OF SUBSTANCE ACROSS 
PLASMA MEMBRANE 
Passive 
transport 
•Movement of substance 
from concentration to 
concentr...
Movement of Substances Into or Out of Cells 
Processes 
Diffusion Osmosis 
Similarities 
• Energy not required 
• Movement...
Molecule to 
be carried 
Section 7-3 
Energy 
Molecule 
being carried 
Figure 7-19 Active Transport 
ACTIVE 
TRANSPORT 
•A...
Facilitated Diffusion Facilitated Diffusion 
•Across gradient 
•High to low 
•No energy required 
•Protein channel 
High 
...
COMPARISON BETWEEN PASSIVE & ACTIVE TRANSPORT 
PASSIVE 
TRANSPORT 
SIMILARITIES ACTIVE 
TRANSPORT 
DIFFERENCES 
Concentrat...
COMPARISON BETWEEN PASSIVE & ACTIVE TRANSPORT 
PASSIVE 
TRANSPORT 
SIMILARITIES ACTIVE 
TRANSPORT 
Transport of substance...
THE END 
I CONTROL 
who 
enters!!
Solutions Observation Discussion Condition 
Hypotonic 
solution 
• Water diffuses into 
the cell by osmosis. 
• The cell s...
Solutions Observation Discussion 
Condition of 
cell 
Hypotonic 
solution 
• Water diffuses into 
the large central 
vacuo...
ACTIVITIES
Cell Membrane Structure 
Sketch and label a phospholipid coloring the heads red 
and the tails blue. 
Hydrophilic 
Hydroph...
List 4 functions of the cell or 
plasma membrane: 
a. Boundary- barrier to environment 
b. Provides protection & support 
...
Correctly color code and identify the 
name for each part of the cell 
membrane. 
A-Phospholipid bilayer 
B-Integral prote...
Match the cell membrane structure or its 
function with the correct letter from the cell 
membrane diagram. 
G-Attracts wa...
Define: 
• Isotonic- equal solutes in solution and cell 
– Equal movement of water in and out 
• Hypertonic- greater solut...
Match with osmotic condition 
• A- Isotonic 
– solution in which the solute concentration is the 
same 
– condition that a...
Label the tonicity for each 
solution (isotonic, hypotonic, or 
hypertonic): 
Hypotonic Isotonic Hypertonic
Label the tonicity for each 
solution (isotonic, hypotonic, or 
hypertonic): 
Hypotonic Isotonic Hypertonic
How can the rate of diffusion be 
affected? 
1. Temperature 
 Increase in temp. increases rate 
2. Size of particles 
 S...
How does osmosis affects cells?
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
BIOLOGY FORM 4 CHAPTER 3 -  MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
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BIOLOGY FORM 4 CHAPTER 3 - MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE

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BIOLOGY FORM 4 CHAPTER 3 - MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE

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BIOLOGY FORM 4 CHAPTER 3 - MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE

  1. 1. BIOLOGY FORM 4 CHAPTER 3 MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE
  2. 2. SUBTOPICS 3.1 - Movement of Substances Across the Plasma Membrane 3.2 – Understanding the Movement of Substances Across the Plasma Membrane in Everyday Life 3.3 – Appreciating the Movement of Substances Across the Plasma Membrane
  3. 3. LEARNING OUTCOMES • To state the substances required by living cells • To state the substances that have to be eliminated from cells • To explain the necessity for movement of substances across the plasma membrane • To describe the structure of the plasma membrane • To describe the permeability of the plasma membrane
  4. 4. Substances to be eliminate from the cells • Water • Nutrient – Glucose – Amino acid – Mineral – Fatty acid – Vitamin • Urea • Toxin
  5. 5. NECESSITY FOR MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANE  To provide nutrients for metabolism & growth;  To supply oxygen for respiration;  To regulate solute concentration & suitable pH for maintaining a stable internal environment for optimal enzymatic activities  To maintain an ion concentration gradient required for nerve & muscle cell activities;  To secrete useful substances, for example, digestive enzymes & hormones;  To eliminate toxic waste products such as urea & carbon dioxide
  6. 6. PLASMA MEMBRANE
  7. 7. Functions of the plasma membrane: 1. Boundary- barrier to environment. Saparates the contents of the cells from their external environment. 2. Regulates what enters and leaves the cell. 3. Provides protection.
  8. 8. The plasma membrane of a cell can be thought of as a gatekeeper: allowing only specific substances in or out passing messages from the external environment to the cell’s interior
  9. 9. Which term is better to describe a plasma membrane? semi-permeable Only allows certain substances to pass through
  10. 10. The general structure of membranes is know as the: fluid mosaic model Fluid refers to the phospholipid bilayer Mosaic refers to the proteins The phospholipid bilayer is like a “lake” in which a variety of proteins “float”.
  11. 11. This model is referred to as the ‘fluid mosaic model’ because the components are free to move independently of each other. Surface view 4.6
  12. 12. The main components of the plasma membrane are: Protein Side view Phospholipid 4.6
  13. 13. Outer & inner membrane surfaces differ.
  14. 14. Let us explain how a bilayer forms
  15. 15. Structure of a phospholipid molecule Hydrophilic head (phosphate) Hydrophobic tail (fatty acid) What happens when a thin layer of phospholipid molecules is spread over the surface of water?
  16. 16. 4.6
  17. 17. 4.6
  18. 18. 4.6 They arrange themselves into a single layer
  19. 19. 4.6 A spherical micelle
  20. 20. Two layers form: a bilayer 4.6 phospholipid bilayers like this are the basic structure of plasma membranes
  21. 21. Phospholipids can move within the membrane The phospholipid bilayer is flexible, and the interior is fluid, allowing lateral movement of molecules
  22. 22. Proteins can move within the Plasma Membrane Side view Surface view
  23. 23. Let us have a look at PROTEINS
  24. 24. PROTEINS  There are proteins on the outer & inner surfaces of the plasma membrane.  Some proteins penetrate partially through the membrane, others penetrate completely.
  25. 25. Transport Proteins 2 types: 1. Channel/pore proteins are embedded in the cell membrane & have a pore for materials to cross 2. Carrier proteins can change shape to move material from one side of the membrane to the other CHANNEL/PORE PROTEINS CARRIER PROTEINS
  26. 26. The phospholipid bilayer only allows CERTAIN materials to cross. polar head nonpolar tails hydrophobic molecules hydrophilic molecules 1. Small non-polar molecules – O2 & CO2 2. Lipid-soluble substances – vitamins ADEK, steroids & alcohols 3. Water molecules (small amount)
  27. 27. The phospholipid bilayer does not polar head allow all materials to cross nonpolar tails hydrophobic molecules hydrophilic molecules cytosol BUT hydrophilic molecules STILL get through. How?
  28. 28. Nonpolar, hydrophobic solutes Polar, ionised, hydrophilic solutes
  29. 29. Charged molecules & ions can enter a cell. How can this be? Move through a protein. Big & polar molecules (glucose, amino acid), charged ions ~~cannot cross and need help of TRANSPORT PROTEIN
  30. 30. Which substances can/cannot pass through the phospholipid bilayer? Small amounts.
  31. 31. Explain why organic solvents such as alcohol, ether and chloroform penetrate membranes more readily than water. Alcohol, ether & chloroform are non-polar Water is polar: repelled by non-polar portions
  32. 32. Recall concept on “Cell surface membrane” which is found in all living cells  Partially-permeable membrane that forms a boundary between the cytoplasm of the cell and the outside.  Controls the passage of substances (small molecules) entering and exiting the cell
  33. 33. MOVEMENT THROUGH THE PLASMA MEMBRANE
  34. 34. LEARNING OUTCOMES  To explain the movement of substances across the plasma membrane through the process of passive transport  To explain the movement of water molecules across the plasma membrane by osmosis,  To explain the movement of substances across the plasma membrane through the process of active transport,  To explain the process of passive transport in living organisms using examples
  35. 35. PASSIVE
  36. 36. PASSIVE TRANSPORT ACTIVE TRANSPORT Cell uses ATP high Weeee!!! low Cell does not use ATP: substances just diffuse through the membrane high low This is going to be hard work!!
  37. 37. DIFFUSION is the movement of molecules or ions from a region of high concentration to region of low concentration down a CONCENTRATION gradient
  38. 38. Describing the process of DIFFUSION Molecules (possess kinetic/movement energy) moving down a concentration gradient Difference in concentration between two regions is called Region A Region B
  39. 39. 51 Diffusion of Liquids
  40. 40. Diffusion • Water, carbon dioxide and other small uncharged particles
  41. 41. The rate of diffusion depends on 1. The steepness of the diffusion gradient  the steeper the gradient, the faster the rate of diffusion faster slower It is an advantage for cells to maintain steep diffusion gradients if rapid transport is required. How is such a gradient kept in the gut?
  42. 42. Blood carries away the digested food
  43. 43. In windy conditions, air outside leaves becomes drier Water diffuses faster through the stomata
  44. 44. At a higher temperature the particles have more kinetic energy and are moving around faster. Therefore in a given time more diffusion will occur.
  45. 45. The surface area of the second cell is much bigger than the first cell due to the folded membrane. The volume of the cells is very similar. Therefore the second cell has a much larger surface area to volume ratio and it increases the rate of diffusion.
  46. 46. The larger the surface area of a membrane through which diffusion is taking place, the faster the diffusion
  47. 47. Surface Area • As the rate of diffusion relies on the surface area. • The parts of organisms that rely on diffusion therefore tend to have a large surface area.
  48. 48. Rate of diffusion decreases rapidly with distance  diffusion is effective over very short distances Squamous epithelial cells line:  Alveoli  Capillary walls
  49. 49. EXAMPLE OF DIFFUSION
  50. 50. Diffusion in lungs  The cells of your lungs exchange oxygen and carbon dioxide through diffusion.
  51. 51. A single air sac 21 blood supply to air sac air breathed in and out diffusion of oxygen diffusion of carbon dioxide O2 CO2 0.03 mm
  52. 52. Diffusion in root hair cells  Plant cells such as root hair cells also take in oxygen and remove carbon dioxide through diffusion.
  53. 53. Leaf O2 and CO2 diffuse into the spaces between cells the ‘veins’ bring water O2 and CO2 diffuse through pores in the epidermis In a thin leaf, the diffusion distance is short 26
  54. 54. Diffusion of O2 & water vapour through stomata
  55. 55. FACILITATED DIFFUSION
  56. 56. Two types of diffusion Simple diffusion: small molecules cross the lipid bilayer Facilitated diffusion: substances cross the bilayer aided by:  channel or  carrier proteins
  57. 57. Difference between channel & carrier proteins: Channel proteins fixed shape Carrier proteins undergo rapid changes in shape Extracellular space Intracellular space
  58. 58. Down or Against a concentration gradient? Simple & Facilitated Diffusion: Active transport:
  59. 59. Which substances enter by facilitated diffusion?  those that cannot diffuse through the phospholipid bilayer such as: 1. Large particles:  glucose  amino acids  proteins 2. Some ions:  Na+ ions  Cl- ions
  60. 60. Facilitated diffusion can occur through a: Non-specific transporter Specific transporter
  61. 61. Carrier proteins:  substance to be transported is bound to a membrane protein
  62. 62. Why does the rate of uptake reach a maximum in facilitated diffusion? Carriers are saturated. Simple diffusion Facilitated diffusion
  63. 63. Facilitated diffusion has three essential characteristics:  it is: 1. Specific 2. Passive 3. Saturates
  64. 64. 85 Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins.
  65. 65. 86 Facilitated Diffusion • Some Carrier proteins do not extend through the membrane. • They bond and drag molecules through the lipid bilayer and release them on the opposite side.
  66. 66. 87 Carrier Proteins • Other carrier proteins change shape to move materials across the cell membrane
  67. 67. Define: Simple diffusion: The passive transport of substances across the plasma membrane Facilitated diffusion: The passive transport of substances across the plasma membrane with the help of transport proteins such as the channel protein and the carrier protein
  68. 68. EXAMPLES OF FACILITATED DIFFUSION
  69. 69. OSMOSIS
  70. 70. Osmosis  is the passage of water molecules from a region of their high concentration to a region of their low concentration through a partially permeable membrane
  71. 71. Water continues to flow until: equilibrium is reached
  72. 72. Three terms are used to compare the solute concentrations of two solutions separated by a membrane: Isotonic Hypotonic Hypertonic
  73. 73. Isotonic solutions [same concentration]
  74. 74. Hypotonic solution Hypertonic solution [lower conc. of solute] [higher conc. of solute]
  75. 75. Water molecules always move from from HYPOTONIC solution to HYPERTONIC solution HYPO  HYPER
  76. 76. Osmosis Partially permeable membrane High Water Concentration means the solution is Hypotonic Loses water by Water molecules Solute molecules cannot pass through the partially permeable membrane There is a net movement of water molecules towards the less concentrated side (in terms of water molecules) until water concentrations equalize. osmosis Low water concentration means the solution is Hypertonic Gains water by osmosis HYPO HYPER
  77. 77. ISOTONIC
  78. 78. HYPERTONIC
  79. 79. HYPOTONIC
  80. 80. Osmosis in Animal Cells
  81. 81. isotonic solution Crenated cells haemolysis hypertonic solution 10 microns hypotonic solution equal movement of water into and out of cells net water movement out of cells net water movement into cells
  82. 82. Name the solutions Osmosis in Red Blood Cells Isotonic Hypotonic Hypertonic
  83. 83. Plant cells in a hypotonic solution: Water enters the cell and fills the vacuole. The plasma membrane pushes against the cell wall making the cell very inflexible. Cells in this state are TURGID.
  84. 84. Plant cells in a hypertonic solution: The cell loses water and goes FLACCID. REASON:  the vacuole becomes flaccid  the cytoplasm stops pushing against the cell wall This state is called PLASMOLYSIS. A cell at this stage is said to be plasmolysed.
  85. 85. HYPOTONIC ISOTONIC HYPERTONIC
  86. 86. Why is it that plant cells do not burst? Presence of a cell wall.
  87. 87. 115 hypotonic hypertonic isotonic hypertonic isotonic hypotonic
  88. 88. Hypertonic Isotonic Hypotonic Plasmolysed Flaccid Turgid PLANT CELLS
  89. 89. Onion epidermal cells were placed in a 1M sucrose solution. What fills the space between the cell wall and the protoplast? Sucrose solution
  90. 90. (1) wilting (2) recovering (1) Wilting. Pant is short of water. The leaf cells are no longer turgid and the leaves curl up and droop. (2 3) Recovered. Water is once more available. The leaf cells take up water by osmosis and become turgid. The leaves are now firm and are held horizontally. Woody plants such as trees and shrubs do not collapse when they wilt but their leaves become limp. (3) recovered
  91. 91. 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.
  92. 92. Potato strips were first placed in either a hypotonic or a hypertonic solution, than in water. Why did potato strips P float & Q sink? PLASMOLYSED TURGID
  93. 93. Osmosis demo • The membrane contains strong sugar solution. • The membrane is stood in a weak sugar solution. • Soon liquid starts to rise up the tube. • Why?
  94. 94. Osmosis demo • Water molecules can diffuse through the membrane from the weak solution to the strong one. • Sugar molecules can not diffuse through because they are too big.
  95. 95. HYPERTONIC HYPOTONIC
  96. 96. Visking tubing 0.5% Sugar solution 0.1% Sugar solution
  97. 97. Visking tubing 0.5% Sugar solution 0.1% Sugar solution Water moves from a dilute solution to a more concentrated one across the partially permeable cell membrane.
  98. 98. Amoeba has a cytoplasm that is hypertonic to the pond water in which it lives What does this lead to? Net flow of water by osmosis over the entire plasma membrane.
  99. 99. What is the role of the contractile vacuole? Expels excess water from the cell
  100. 100. Amoeba may also adjust the quantity of dissolved substances in the cytoplasm Amoeba actively pumps out ions. How does this help in the contractile vacuole working more efficiently? Less water enters and so the contractile vacuole can cope with the water to be pumped out.
  101. 101. Why the use of excess fertilizer caused wilting in plant?
  102. 102. Wilting of Plants • Problems can arise if chemical fertilisers are added in excess to the soil. • The soil solutions becomes hypertonic to the cell sap of the root hair cells. • Water moves out of the plant by osmosis. • When flaccidity spreads throughout the plant, wilting occurs.
  103. 103. Explain these preservation process
  104. 104. Preservation of Food • Food can be preserved by using salt or sugar. • When salt or sugar is added to the food, it creates a hypotonic condition for the microorganisms that spoil the food. • Water passes out from the microorganisms into the concentrated solution. This results in slower growth of the microorganisms or even death.
  105. 105. ACTIVE TRANSPORT
  106. 106. Active Transport Problem: • Diffusion is very slow • moves substances down a concentration gradient. • Many substances are needed by organisms in larger amounts • need to be accumulated in cells against the concentration gradient. • Energy needed to move the needed substances across the cell membrane  ACTIVE TRANSPORT
  107. 107. Active Transport Active transport occurs using channel proteins.
  108. 108. Movement of substances by active transport is usually in one direction only. What about in diffusion? Direction is reversible in diffusion.
  109. 109. ATP supplies the energy for active transport. What is the use of energy? The carrier proteins need energy to keep changing shape.
  110. 110. EXAMPLES OF ACTIVE TRANSPORT
  111. 111. 168 Sodium-Potassium Pump in plasma membrane of neurones 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential
  112. 112. Active transport in small intestine
  113. 113. Active transport in root hair cells
  114. 114. LEARNING OUTCOMES • To explain the process of active transport in living organisms using examples, • To compare and contrast passive transport & active transport.
  115. 115. Remember the Examples  Examples of diffusion: = gaseous exchange between the alveolus & the blood capillaries, blood capillaries & body cells  Examples of osmosis: Absorption of water from soil solution by plant root hairs Reabsorption of water by kidney tubules  Examples of facilitated diffusion : - transportation of glucose, amino acids & mineral ions across the membrane of the vilus at the ileum & body cells.  Example of active transport : - absorption of potassium ions from pond water by algae Nitella sp., - the intake of mineral ions by the plant root hairs, - Na+/ K+ protein pumps in the plasma membrane of neurones
  116. 116. MOVEMENT OF SUBSTANCE ACROSS PLASMA MEMBRANE Passive transport •Movement of substance from concentration to concentration •Move DOWN their concentration gradient •DOES NOT require energy Simple diffusion Osmosis Facilitated diffusion Active transport •Movement of substance from concentration to concentration •Move AGAINST their concentration gradient •Requires energy
  117. 117. Movement of Substances Into or Out of Cells Processes Diffusion Osmosis Similarities • Energy not required • Movement of substances down a concentration gradient • Refers only to water molecules • Takes place across a partially permeable membrane • Refers to any substance, gaseous or liquid • Membrane is not required Differences
  118. 118. Molecule to be carried Section 7-3 Energy Molecule being carried Figure 7-19 Active Transport ACTIVE TRANSPORT •Against concentration gradient •Requires energy •Carrier protein Low concentration High concentration
  119. 119. Facilitated Diffusion Facilitated Diffusion •Across gradient •High to low •No energy required •Protein channel High Concentration Low Concentration Cell Membrane Glucose molecules Protein channel Section 7-3
  120. 120. COMPARISON BETWEEN PASSIVE & ACTIVE TRANSPORT PASSIVE TRANSPORT SIMILARITIES ACTIVE TRANSPORT DIFFERENCES Concentration gradient Cellular energy Outcome of the process Occurs in Name of process Examples
  121. 121. COMPARISON BETWEEN PASSIVE & ACTIVE TRANSPORT PASSIVE TRANSPORT SIMILARITIES ACTIVE TRANSPORT Transport of substances across the plasma membrane Need a difference of concentration gradient between extracellular environment & the cell DIFFERENCES Follow Concentration gradient Against Does not expend energy Cellular energy Need to expend energy Until an equilibrium is reached Outcome of the process Depends on the cells requirement (no need to reach an equilibrium) Non-living & living organisms Occurs in Living organisms only Simple diffusion, osmosis, facilitated diffusion Name of process Active transport Examples
  122. 122. THE END I CONTROL who enters!!
  123. 123. Solutions Observation Discussion Condition Hypotonic solution • Water diffuses into the cell by osmosis. • The cell swell up and eventually burst The condition is known as haemolysis. Isotonic solution • Water diffuses into and out of the cell at equal rates. • No net movement of water. The cell retain their normal shape. Hypertonic solution • Water diffuses out of the cell by osmosis. • The cell shrinks. The red blood cell is said to have undrgone creanation.
  124. 124. Solutions Observation Discussion Condition of cell Hypotonic solution • Water diffuses into the large central vacuole by osmosis. • The large central vacuole expands, causing the cell to swell. The cell is said to be turgid Isotonic solution • Water diffuses into and out of the cell at equal rates. The cell retain their normal shape Hypertonic solution • Water diffuses out of the large central vacuole by osmosis. • Both the vacuole and cytoplasm lose water to surroundings and shrink. • The plasma membrane pulls away from the cell This condition is called plasmolysis. The plant cell becomes flaccid and less turgid.
  125. 125. ACTIVITIES
  126. 126. Cell Membrane Structure Sketch and label a phospholipid coloring the heads red and the tails blue. Hydrophilic Hydrophobic Hydrophilic
  127. 127. List 4 functions of the cell or plasma membrane: a. Boundary- barrier to environment b. Provides protection & support c. Regulates what enters and leaves cells d. Maintains homeostasis
  128. 128. Correctly color code and identify the name for each part of the cell membrane. A-Phospholipid bilayer B-Integral protein C-Peripheral protein E-Cholesterol F-Fatty acid tails G-Phosphate heads H-Glycoprotein I-Glycolipids
  129. 129. Match the cell membrane structure or its function with the correct letter from the cell membrane diagram. G-Attracts water I-Helps maintain flexibility of membrane E-Involved in cell-to-cell recognition F-Repels water A-Make up the bilayer B-Help transport certain materials across the cell membrane
  130. 130. Define: • Isotonic- equal solutes in solution and cell – Equal movement of water in and out • Hypertonic- greater solutes in solution when compared to the cell – Causes water to be drawn out of cell & shrink • Hypotonic- lower solute in solution when compared to the cell – Causes water to enter cell and swell
  131. 131. Match with osmotic condition • A- Isotonic – solution in which the solute concentration is the same – condition that animal cells require • B- Hypertonic – plant cell loses turgor pressure (Plasmolysis) – solution with a higher solute concentration • C-Hypotonic – solution with a lower solute concentration – condition plant cells require – red blood cell bursts (cytolysis) – plant cell with good turgor pressure – solution with a high water concentration
  132. 132. Label the tonicity for each solution (isotonic, hypotonic, or hypertonic): Hypotonic Isotonic Hypertonic
  133. 133. Label the tonicity for each solution (isotonic, hypotonic, or hypertonic): Hypotonic Isotonic Hypertonic
  134. 134. How can the rate of diffusion be affected? 1. Temperature  Increase in temp. increases rate 2. Size of particles  Small sizes diffuse faster than large ones 3. Thickness of the barrier  Thicker walls, slower rate 4. Concentration gradient  Greater concentration gradient, faster rate 5. Surface area  Increase S.A., increase rate
  135. 135. How does osmosis affects cells?

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