2. Content
The iGCSE
Biology
course
Section 1: The nature and variety of living
organisms
Section 2: Structures and functions in
living organisms
Section 3: Reproduction and inheritance
Section 4: Ecology and the environment
Section 5: Use of biological resources
3. Content
The iGCSE
Biology
course
Section 1: The nature and variety of living
organisms
Section 2: Structures and functions in
living organisms
Section 3: Reproduction and inheritance
Section 4: Ecology and the environment
Section 5: Use of biological resources
4. Content
Section 2
Structures
and
functions
in living
organisms
a) Levels of organisation
b) Cell structure
c) Biological molecules
d) Movement of substances
into and out of cells
e) Nutrition
f) Respiration
g) Gas exchange
h) Transport
i) Excretion
j) Coordination and response
5. Content
Section 2
Structures
and
functions
in living
organisms
a) Levels of organisation
b) Cell structure
c) Biological molecules
d) Movement of substances
into and out of cells
e) Nutrition
f) Respiration
g) Gas exchange
h) Transport
i) Excretion
j) Coordination and response
6. Content
Lesson 1
a) Levels of
organisation
2.1 describe the levels of organisation within
organisms: organelles, cells, tissues,
organs and systems.
7. Content
Lesson 1
b) Cell
structure
2.2 describe cell structures, including the
nucleus, cytoplasm, cell membrane, cell
wall, chloroplast and vacuole
2.3 describe the functions of the nucleus,
cytoplasm, cell membrane, cell wall,
chloroplast and vacuole
2.4 compare the structures of plant and animal
cells.
12. Levels of Organisation
A. Cells
Animal
Cell
membrane
Controls the passage
of substances into
and out of the cell.
Cytoplasm
Nucleus
13. Levels of Organisation
A. Cells
Animal
Cell
membrane
Controls the passage
of substances into
and out of the cell.
Cytoplasm
Most chemical
reactions occur here
Nucleus
14. Levels of Organisation
A. Cells
Animal
Cell
membrane
Controls the passage
of substances into
and out of the cell.
Cytoplasm
Most chemical
reactions occur here
Nucleus
Controls the
activities of the cell
17. Levels of Organisation
A. Cells
Plant
Cell
membrane
Cytoplasm
Cellulose
cell wall
Strengthens the cell
Nucleus
18. Levels of Organisation
A. Cells
Plant
Cell
membrane
Cytoplasm
Cellulose
cell wall
Strengthens the cell
Permanent
vacuole
Contains cell sap
Nucleus
19. Levels of Organisation
A. Cells
Plant
Cell
membrane
Cytoplasm
Cellulose
cell wall
Strengthens the cell
Permanent
vacuole
Contains cell sap
Chloroplast Absorbs light energy to make
food through photosynthesis
Nucleus
20. Comparing plant and animal cells
Found in both plant
and animal cells
Found in plant cells
only
21. Comparing plant and animal cells
Found in both plant
and animal cells
Found in plant cells
only
Nucleus
Cytoplasm
Cell membrane
22. Comparing plant and animal cells
Found in both plant
and animal cells
Found in plant cells
only
Nucleus Chloroplasts
Cytoplasm Cell walls
Cell membrane
Permanent
vacuoles
23. Specialised cells
The egg cell , or ovum,
is much larger than
other cells so that it
can carry food reserves
for the developing
embryo if fertilisation
takes place.
24. Specialised cells
Sperms cells have
elongated tails that
enable them to swim
towards the egg (ovum)
following ejaculation
into the vagina.
25. Specialised cells
Red blood cells do not
have a nucleus, so they
are able to pack in more
haemoglobin molecules,
and so carry even more
oxygen.
26. Specialised cells
Nerve cells are very
elongated, and some
may be over a metre in
length. They carry
electrical signals
around the body.
27. Levels of Organisation
B Tissues
Tissues are groups of similar
cells that are able to work
together to carry out a
specific function.
28. Levels of Organisation
B Tissues
eg. Muscle tissue
Muscle tissue is very
specialised, and has
the ability to contract
and also to conduct
electrical impulses.
There are three types
of muscle: smooth,
skeletal and cardiac.
29. Levels of Organisation
C Organs
Organs consist of groups of
tissues working together to
perform specific functions.
30. Levels of Organisation
C Organs
eg. the Heart
The heart is a
muscular organ found
in all animals with a
circulatory system. It
is composed mostly of
cardiac muscle and
connective tissue, but
also nervous tissue
and blood.
31. Levels of Organisation
D Organ system
An organ system is a group
of organs that work together
to perform a certain task.
32. Levels of Organisation
D Organ system
eg. the Digestive system
The digestive system
consists of numerous
organs, including the
stomach and liver. It
digests food and
enables it to be
absorbed into the
blood stream.
34. Lesson 1
c) Biological
molecules
2.5 identify the chemical elements present in
carbohydrates, proteins and lipids (fats and
oils)
2.6 describe the structure of carbohydrates,
proteins and lipids as large molecules made up
from smaller basic units: starch and glycogen
from simple sugar; protein from amino acids;
lipid from fatty acids and glycerol
2.7 describe the tests for glucose and starch
2.8 understand the role of enzymes as
biological catalysts in metabolic reactions
2.9 understand how the functioning of enzymes
can be affected by changes in temperature,
including changes due to change in active site
2.10 understand how the functioning of
enzymes can be affected by changes in
active site caused by changes in pH
2.11 describe experiments to investigate how
enzyme activity can be affected by changes in
temperature.
42. Biological molecules
carbohydrates
Sugar
Different foods contain
different kinds of sugar.
Eg fruit contains fructose
or glucose. Lactose is in
milk. Table sugar is
sucrose.
Sugar gives us
energy, so we call
it an energy food.
Starch
Cellulose
43. Biological molecules
carbohydrates
Sugar
Different foods contain
different kinds of sugar.
Eg fruit contains fructose
or glucose. Lactose is in
milk. Table sugar is
sucrose.
Sugar gives us
energy, so we call
it an energy food.
Starch
Starch is found
particularly in
bread, potatoes
and cereals.
Starch is a storage
molecule, but it does
provide us with
energy.
Cellulose
44. Biological molecules
carbohydrates
Sugar
Different foods contain
different kinds of sugar.
Eg fruit contains fructose
or glucose. Lactose is in
milk. Table sugar is
sucrose.
Sugar gives us
energy, so we call
it an energy food.
Starch
Starch is found
particularly in
bread, potatoes
and cereals.
Starch is a storage
molecule, but it does
provide us with
energy.
Cellulose
Cellulose is found
in plant cell walls
It is a structural
molecule, and
supports the plant
cell.
45. Biological molecules
Fats
Fats also contain C, H and O, but relatively less
O. Fats occur in both plant and animal foods.
Fats – solid at room temperatures.
Oils - liquid at room temperatures.
46. Biological molecules
Fats
Fats also contain C, H and O, but relatively less
O. Fats occur in both plant and animal foods.
Fats – solid at room temperatures.
Oils - liquid at room temperatures.
Fats also give us energy. They also provide
insulation in humans and other mammals, and are
energy stores.
48. Biological molecules
Proteins
Proteins contain C, H and O, and also some
nitrogen (N) and a little suplhur (S).
Proteins are found in milk, eggs, meat and fish.
Proteins are needed for
growth and body-
building (muscles and
skin), and they are also
used to make enzymes.
59. ENZYMES
Enzymes are biological catalysts – they speed up
the rate of chemical reactions going on inside
living things.
What are the features of enzymes?
60. ENZYMES
Enzymes are biological catalysts – they speed up
the rate of chemical reactions going on inside
living things.
What are the features of enzymes?
• Enzymes are globular proteins
• Every enzyme has an area called its active site
• Enzymes are specific
• Enzymes are affected by temperature and pH
61. ENZYMES
• Commonly named by adding the ending
“-ase” to the substrate molecule being
acted upon.
• Eg. sucrase works on sucrose, lipase
works on lipose.
• A few enzymes are known by common
names, eg. pepsin, trypsin
66. Enzymes and Temperature
Time (minutes)
Temperature
(
o
C)
10 20 30 40 50 60
10
20
30
40
50
60
An experiment
was carried out
to investigate
how temperature
affects the rate
at which an
enzyme converts
starch into sugar.
67. Enzymes and Temperature
Time (minutes)
Temperature
(
o
C)
10 20 30 40 50 60
10
20
30
40
50
60
The results are
shown in this
table. A black
circle means that
there is still
starch present.
An orange dot
means that there
is no starch
present.
68. Enzymes and Temperature
Temperature (oC) 10 20 30 40 50 60
Time taken for starch to
disappear (min.)
1. Plot a graph with temperature
along the x-axis (across) and
time up the y-axis.
2. What can you conclude about
this investigation? How does
temperature affect the
action of enzymes.
3. Find out what ‘denatured’
means. How does it apply to
this investigation?
69. Lesson 1
d) Movement
of substances
into and out of
cells
2.12 understand definitions of diffusion,
osmosis and active transport
2.13 understand that movement of
substances into and out of cells can be by
diffusion, osmosis and active transport
2.14 understand the importance in
plants of turgid cells as a means of
support
2.15 understand the factors that affect
the rate of movement of substances into
and out of cells, to include the effects of
surface area to volume ratio, temperature
and concentration gradient
2.16 describe experiments to investigate
diffusion and osmosis using living and
non-living systems.
75. What is diffusion?
Other examples of diffusion
include:
Smell of frying bacon from a
kitchen
Leaking of air from inside a
balloon
Sugar dissolving in a cup of tea
76. What is diffusion?
Diffusion is the movement of
particles from areas of high
concentration to areas of low
concentration until they are
evenly spread. Diffusion
depends upon the random
movement of particles.
77. What is diffusion?
Diffusion is the movement of
particles from areas of high
concentration to areas of low
concentration until they are
evenly spread. Diffusion
depends upon the random
movement of particles.
Diffusion is slower in liquids
than in gases because liquid
particles are not as free to
move as gas particles.
82. Diffusion in living organisms
Eg. movement of oxygen in Amoeba
Low oxygen
concentration
High oxygen
concentration
83. Diffusion in living organisms
Eg. movement of oxygen in Amoeba
Low oxygen
concentration
High oxygen
concentration
Oxygen will move from a high concentration outside the
cell to a lower concentration inside the cell. It is moving
from high to low – i.e. down a concentration gradient.
84. Diffusion in living organisms
Where diffusion occurs
in living organisms, the
surfaces across which
gases are exchanged
are often specialised by
having LARGE
SURFACE AREAS to
increase the rate at
which diffusion can
occur. Eg. alveoli in the lungs provide a
huge surface area for the
exchange of oxygen and carbon
dioxide.
86. What is osmosis?
Osmosis is:
a special type of diffusion
it is the diffusion on water
molecules from an area of high
water concentration to an area of
lower water concentration through a
partially permeable membrane.
90. What is osmosis?
A partially permeable what ……… ?
Membrane!
Higher water
concentration (fewer
solute particles)
Lower water
concentration (more
solute particles)
91. What is osmosis?
A partially permeable what ……… ?
Membrane!
Higher water
concentration (fewer
solute particles)
Lower water
concentration (more
solute particles)
92. What is osmosis?
Water particles will continue to move
until there are equal numbers of water
molecules on both sides of the membrane.
Higher water
concentration (fewer
solute particles)
Lower water
concentration (more
solute particles)
93. What is osmosis?
More concentrated solution
inside
Less concentrated solution
outside (more DILUTE)
WATER
WATER
In root hair cells water moves
from the surrounding soil into
the cell by osmosis, along a
concentration gradient
99. Osmosis experiments
Weighed
potato chip
Placed in
pure water
Water enters by
osmosis, potato
chip weighs more
Placed in
concentrated
sugar solution
Water leaves by
osmosis, potato
chip weighs less
101. What is Active Transport?
Active transport is moving
substances against a
concentration gradient.
102. What is Active Transport?
Active transport is moving
substances against a
concentration gradient.
Imagine
trying to
push a trolley
up a hill
103. What is Active Transport?
Active transport is moving
substances against a
concentration gradient.
Imagine
trying to
push a trolley
up a hill
-It will
require
ENERGY!
104. What is Active Transport?
Similarly, when substances are moved into a cell
where there is already a higher concentration,
then ENERGY from respiration will be required.
105. What is Active Transport?
Similarly, when substances are moved into a cell
where there is already a higher concentration,
then ENERGY from respiration will be required.
Root hair cell with a high
concentration of nitrate ions.
Soil with a lower concentration of
nitrate ions.
106. What is Active Transport?
Similarly, when substances are moved into a cell
where there is already a higher concentration,
then ENERGY from respiration will be required.
Root hair cell with a high
concentration of nitrate ions.
Soil with a lower concentration of
nitrate ions.
Energy will be used to ‘pull’
nitrate ions from the
surrounding soil into the cell
107. What is Active Transport?
Active transport also
occurs in the human
body. For example, in
the kidneys, sugar is
recovered back into the
blood by transporting it
against a concentration
gradient.
109. Factors affecting the movement of
substances
Surface area
to volume
ratio
Temperature
Concentration
gradient
110. Factors affecting the movement of
substances
Surface area
to volume
ratio
The bigger the surface area compared
to the volume, the faster the rate of
movement of substances – eg. the lungs
Temperature
Concentration
gradient
111. Factors affecting the movement of
substances
Surface area
to volume
ratio
The bigger the surface area compared
to the volume, the faster the rate of
movement of substances – eg. the lungs
Temperature
As temperature increases, particles gain
kinetic energy. They therefore move
faster, and so diffusion, osmosis and
active transport all occur at a faster
rate.
Concentration
gradient
112. Factors affecting the movement of
substances
Surface area
to volume
ratio
The bigger the surface area compared
to the volume, the faster the rate of
movement of substances – eg. the lungs
Temperature
As temperature increases, particles gain
kinetic energy. They therefore move
faster, and so diffusion, osmosis and
active transport all occur at a faster
rate.
Concentration
gradient
The bigger the concentration difference, for
example inside and outside of the cell, the
faster substances will move – think about a
steeper hill?
113. End of Section 2 Lesson 1
In this lesson we have covered:
Levels of organisation
Cell structure
Biological molecules
Movement of substances into and out of cells
