IGCSE COMBINED SCIENCE
Biology: B1 Cells
B1.01 Characteristics of living things
● Seven Life Processes
○ Movement: An action by an organism or part of an organism causing a change in
position/place
○ Respiration: Chemical reactions in the cells that break down nutrients molecules to release
energy for metabolism
○ Sensitivity: Ability to detect & respond to changes in the environment
○ Growth: Permanent increase in size
○ Reproduction: the processes that make more of the same kind of organism
es
○ Excretion: Removal from organisms of waste products of metabolism, toxic materials &
substances in excess of requirements
○ Nutrition: Taking in minerals for energy, growth & development
ot
B1.02 Cells
● Cells → Tissues→ Organs → Organ Systems → Organisms
● Importance
N
○ Simplest part of a living structure that can operate as an independent unit
○ Made up of organelles
SE
■ Structures inside living cells that carry out specific functions leading to the survival of
the cell (eg. Nucleus)
● Magnification
○ Hand lens magnifies up to× 10
○ Good light microscope magnifies up to × 1500 C
○ Electron microscope magnifies up to× 10 million
IG
𝑠𝑖𝑧𝑒 𝑖𝑛 𝑑𝑟𝑎𝑤𝑖𝑛𝑔
○ Magnification = 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑟𝑒𝑎𝑙 𝑜𝑏𝑗𝑒𝑐𝑡
● Cell Structure
ay
Part of a cell Can be observed by Structure & functions
Cell Membrane Light microscope ● Thin layer of protein & fat
nj
(Plant & Animal cell) ● Partially permeable
● Controls what goes in & out of the cell (ie. movement of glucose)
● Allows simple substances(𝑂2,𝐶𝑂2,𝐻2𝑂) to pass
Sa
● Surrounds the cytoplasm
Cell Wall Light microscope ● Made of cellulose (type of polysaccharide)
(Plant cell only) ● Fully permeable (little space between fibres)
a
● Protection against injury for the plant cells
ni
● Gives the cell its shape
● Prevents the plant from bursting when too much water enters it
So
Nucleus Light microscope ● Controls all cellular activities
(Plant & Animal cell) ● Contains genetic information arranged in chromosomes (made of
DNA)
○ Chromosomes can only be seen when the cell is
dividing; become short & thick
Cytoplasm Light microscope ● Contains cytosol (semi liquid 70% water)
(Plant & Animal cell) ● Organelles found here
● Respiration & chemical reactions occur
Vacuole Light microscope ● Sac inside the cell stores salts & sugars
, (Plant & Animal cell) ● Keeps the shape of the cell
● Plant cells: single large vacuole containing cell sap (liquid
containing sugars & other substances dissolved in water)
● Animal cells: many small vacuoles (vesicles) containing
nutrients/water
Chloroplasts Electron ● An organelle containing chlorophyll
(Plant cell only) microscope ○ Absorbs energy from the sunlight (used for
photosynthesis)
● Site of photosynthesis
es
ot
N
SE
● Specialised cells
Type of cell Location Function C
Adaptation Image
IG
Palisade Cell Beneath the Photosynthesi ● Regular shape
(P) epidermis of s ○ Many can fit in a
a leaf small space
● Large vacuole restricts
ay
chloroplasts to a region of
periphery; closer to the
outside of the cell (absorb
nj
more sunlight)
● Cell wall is very thin for fast
diffusion
Sa
Root Hair Cell Near the end Absorb water ● Large surface area increase
(P) of the plant & mineral salts rate of absorption
roots ● Filled with mitochondria;
a
specialised for active
transport of mineral ions
ni
from the soil to roots
● Presence of sap vacuole
lowers its water potential for
So
water to be absorbed by
osmosis
Red Blood Cell In the blood Transport ● Biconcave shape increases
(A) of mammals oxygen the surface area to volume
ratio which allows faster
absorption & release of
dissolved oxygen
● Doesn’t contain a nucleus;
more space to store
, haemoglobin
Ciliated Lining of the Move mucus ● Thin layer of moving
Epithelial Cell trachea & upwards ‘hairs’(cillia) traps & mozes
(A) bronchi dust & bacteria
B2: Movement in & Out of Cells
B2.01 Diffusion
es
● Net movement of molecules & ions from a region of higher concentration to a region of lower
concentration down a concentration gradient as a result of their random movement
○ Until equilibrium is reached
ot
● Equilibrium: when the concentrations are equal
● Concentration gradient: difference between the concentration of molecules in 2 regions
● Only small molecules (eg.𝑂2&𝐻2𝑂) can cross the cell membrane by diffusion
N
○ Doesn’t require any energy from the cell
● Factors influencing a higher rate of diffusion:
SE
○ Higher temperature
■ Provides the particles with more kinetic energy
○ Larger surface area
■ Larger area to act on
○ Larger concentration gradient
C
IG
■ Larger difference in the high & low concentrations increases diffusion rate
● Higher temperature provides particles more kinetic energy: increasing rate of diffusion
● Importance:
○ Gases
ay
■ Necessary for gas exchange
○ Water as the solvent
■ Plants can’t obtain minerals unless they are dissolved in water
nj
■ Enzymes & hormones can’t be secreted unless they are dissolved in water
● Examples in Plant Cells
Sa
○ Photosynthesis
■ 𝐶𝑂2diffuses into leaves via the stomata
■ Oxygen produced diffuses out from the leaves via stomata
● Example in Animal Cells
a
○ Gas Exchange
ni
■ Oxygen diffuses from the lungs (high concentration) & into the blood (low
concentration)
So
■ 𝐶𝑂2diffuses out of blood capillaries & into the lungs
B2.02 Osmosis
● Net movement of water molecules from a region of higher water potential (dilute solution) to a region of
lower water potential (concentrated solution), through a partially permeable membrane
● (Specialised form of diffusion): Diffusion of water across a partially permeable membrane (eg.Visking
tube/cell membrane)
● Importance:
○ Plants only transpire by osmosis
■ Water from soil diffuses into root hair cells
● Diffuses across cortex cells & into xylem vessels & taken up the leaf
, ● Diffuses across the mesophyll cells & out of the stomata
● In Plant Cells
○ Do not burst in pure water
○ Will take in water by osmosis through its cell membrane
■ Water goes in the cytoplasm & vacuole will swell (turgid)
■ Cell wall stops the cell from bursting; restricts efforts of cytoplasm to move out
○ If there is a lower water concentration outside the plant, cell water will move out of the cell until
the concentrations are equal
■ If the concentration gradient is too high, the cell membrane will move away from the
cell wall (plasmolysis)
● Cell will become flaccid; plant will wilt
es
● In Animal Cells
○ Bursts in pure water
○ Absorbs water by osmosis; if concentration gradient is too high, cell will burst
ot
○ If there is a lower water concentration outside the cell, water will move out until the
concentrations are equal
■ If the concentration gradient is too high, the cell will shrivel
N
B3: Biological Molecules
B3.01 Water
SE
● Functions
○ Main component of living organisms
■ Inorganic biological molecules
■ 70% of the human body weight
C
○ Medium for metabolic reactions to take place in an organism
■ Metabolism: Chemical reactions that take place inside the body
IG
○ Solvents for most substances
○ Regulation of body temperature
○ Transporting of dissolved substances
ay
■ Digested food & oxygen must be dissolved in water found in blood before being
transported
■ Waste products (eg.𝐶𝑂2) need to be dissolved in water found in blood to be
nj
transported away
○ Organisms will die if they do not have enough water
Sa
B3.02 Carbohydrates
● Made up of carbon, hydrogen & oxygen
● Organic biological molecule
● Sugars
a
○ Sweet; soluble in water
ni
○ Used during respiration to provide energy
○ Monosaccharides (single sugars)
■ Small molecules that can’t be digested (broken down) into simpler substances
So
■ Small enough to diffuse across cell membranes into the cells
■ Eg. Glucose, Fructose, Galactose (𝐶6𝐻12𝑂6 )
○ Disaccharides (double sugars)
■ Made up of two molecules of monosaccharides that are chemically bonded together
■ Eg. Maltose, sucrose, lactose ( 𝐶12𝐻22𝑂11 )
● Polysaccharides
○ Complex carbohydrates made up of many monosaccharides chemically bonded together
○ Insoluble in water; not sweet
Biology: B1 Cells
B1.01 Characteristics of living things
● Seven Life Processes
○ Movement: An action by an organism or part of an organism causing a change in
position/place
○ Respiration: Chemical reactions in the cells that break down nutrients molecules to release
energy for metabolism
○ Sensitivity: Ability to detect & respond to changes in the environment
○ Growth: Permanent increase in size
○ Reproduction: the processes that make more of the same kind of organism
es
○ Excretion: Removal from organisms of waste products of metabolism, toxic materials &
substances in excess of requirements
○ Nutrition: Taking in minerals for energy, growth & development
ot
B1.02 Cells
● Cells → Tissues→ Organs → Organ Systems → Organisms
● Importance
N
○ Simplest part of a living structure that can operate as an independent unit
○ Made up of organelles
SE
■ Structures inside living cells that carry out specific functions leading to the survival of
the cell (eg. Nucleus)
● Magnification
○ Hand lens magnifies up to× 10
○ Good light microscope magnifies up to × 1500 C
○ Electron microscope magnifies up to× 10 million
IG
𝑠𝑖𝑧𝑒 𝑖𝑛 𝑑𝑟𝑎𝑤𝑖𝑛𝑔
○ Magnification = 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑟𝑒𝑎𝑙 𝑜𝑏𝑗𝑒𝑐𝑡
● Cell Structure
ay
Part of a cell Can be observed by Structure & functions
Cell Membrane Light microscope ● Thin layer of protein & fat
nj
(Plant & Animal cell) ● Partially permeable
● Controls what goes in & out of the cell (ie. movement of glucose)
● Allows simple substances(𝑂2,𝐶𝑂2,𝐻2𝑂) to pass
Sa
● Surrounds the cytoplasm
Cell Wall Light microscope ● Made of cellulose (type of polysaccharide)
(Plant cell only) ● Fully permeable (little space between fibres)
a
● Protection against injury for the plant cells
ni
● Gives the cell its shape
● Prevents the plant from bursting when too much water enters it
So
Nucleus Light microscope ● Controls all cellular activities
(Plant & Animal cell) ● Contains genetic information arranged in chromosomes (made of
DNA)
○ Chromosomes can only be seen when the cell is
dividing; become short & thick
Cytoplasm Light microscope ● Contains cytosol (semi liquid 70% water)
(Plant & Animal cell) ● Organelles found here
● Respiration & chemical reactions occur
Vacuole Light microscope ● Sac inside the cell stores salts & sugars
, (Plant & Animal cell) ● Keeps the shape of the cell
● Plant cells: single large vacuole containing cell sap (liquid
containing sugars & other substances dissolved in water)
● Animal cells: many small vacuoles (vesicles) containing
nutrients/water
Chloroplasts Electron ● An organelle containing chlorophyll
(Plant cell only) microscope ○ Absorbs energy from the sunlight (used for
photosynthesis)
● Site of photosynthesis
es
ot
N
SE
● Specialised cells
Type of cell Location Function C
Adaptation Image
IG
Palisade Cell Beneath the Photosynthesi ● Regular shape
(P) epidermis of s ○ Many can fit in a
a leaf small space
● Large vacuole restricts
ay
chloroplasts to a region of
periphery; closer to the
outside of the cell (absorb
nj
more sunlight)
● Cell wall is very thin for fast
diffusion
Sa
Root Hair Cell Near the end Absorb water ● Large surface area increase
(P) of the plant & mineral salts rate of absorption
roots ● Filled with mitochondria;
a
specialised for active
transport of mineral ions
ni
from the soil to roots
● Presence of sap vacuole
lowers its water potential for
So
water to be absorbed by
osmosis
Red Blood Cell In the blood Transport ● Biconcave shape increases
(A) of mammals oxygen the surface area to volume
ratio which allows faster
absorption & release of
dissolved oxygen
● Doesn’t contain a nucleus;
more space to store
, haemoglobin
Ciliated Lining of the Move mucus ● Thin layer of moving
Epithelial Cell trachea & upwards ‘hairs’(cillia) traps & mozes
(A) bronchi dust & bacteria
B2: Movement in & Out of Cells
B2.01 Diffusion
es
● Net movement of molecules & ions from a region of higher concentration to a region of lower
concentration down a concentration gradient as a result of their random movement
○ Until equilibrium is reached
ot
● Equilibrium: when the concentrations are equal
● Concentration gradient: difference between the concentration of molecules in 2 regions
● Only small molecules (eg.𝑂2&𝐻2𝑂) can cross the cell membrane by diffusion
N
○ Doesn’t require any energy from the cell
● Factors influencing a higher rate of diffusion:
SE
○ Higher temperature
■ Provides the particles with more kinetic energy
○ Larger surface area
■ Larger area to act on
○ Larger concentration gradient
C
IG
■ Larger difference in the high & low concentrations increases diffusion rate
● Higher temperature provides particles more kinetic energy: increasing rate of diffusion
● Importance:
○ Gases
ay
■ Necessary for gas exchange
○ Water as the solvent
■ Plants can’t obtain minerals unless they are dissolved in water
nj
■ Enzymes & hormones can’t be secreted unless they are dissolved in water
● Examples in Plant Cells
Sa
○ Photosynthesis
■ 𝐶𝑂2diffuses into leaves via the stomata
■ Oxygen produced diffuses out from the leaves via stomata
● Example in Animal Cells
a
○ Gas Exchange
ni
■ Oxygen diffuses from the lungs (high concentration) & into the blood (low
concentration)
So
■ 𝐶𝑂2diffuses out of blood capillaries & into the lungs
B2.02 Osmosis
● Net movement of water molecules from a region of higher water potential (dilute solution) to a region of
lower water potential (concentrated solution), through a partially permeable membrane
● (Specialised form of diffusion): Diffusion of water across a partially permeable membrane (eg.Visking
tube/cell membrane)
● Importance:
○ Plants only transpire by osmosis
■ Water from soil diffuses into root hair cells
● Diffuses across cortex cells & into xylem vessels & taken up the leaf
, ● Diffuses across the mesophyll cells & out of the stomata
● In Plant Cells
○ Do not burst in pure water
○ Will take in water by osmosis through its cell membrane
■ Water goes in the cytoplasm & vacuole will swell (turgid)
■ Cell wall stops the cell from bursting; restricts efforts of cytoplasm to move out
○ If there is a lower water concentration outside the plant, cell water will move out of the cell until
the concentrations are equal
■ If the concentration gradient is too high, the cell membrane will move away from the
cell wall (plasmolysis)
● Cell will become flaccid; plant will wilt
es
● In Animal Cells
○ Bursts in pure water
○ Absorbs water by osmosis; if concentration gradient is too high, cell will burst
ot
○ If there is a lower water concentration outside the cell, water will move out until the
concentrations are equal
■ If the concentration gradient is too high, the cell will shrivel
N
B3: Biological Molecules
B3.01 Water
SE
● Functions
○ Main component of living organisms
■ Inorganic biological molecules
■ 70% of the human body weight
C
○ Medium for metabolic reactions to take place in an organism
■ Metabolism: Chemical reactions that take place inside the body
IG
○ Solvents for most substances
○ Regulation of body temperature
○ Transporting of dissolved substances
ay
■ Digested food & oxygen must be dissolved in water found in blood before being
transported
■ Waste products (eg.𝐶𝑂2) need to be dissolved in water found in blood to be
nj
transported away
○ Organisms will die if they do not have enough water
Sa
B3.02 Carbohydrates
● Made up of carbon, hydrogen & oxygen
● Organic biological molecule
● Sugars
a
○ Sweet; soluble in water
ni
○ Used during respiration to provide energy
○ Monosaccharides (single sugars)
■ Small molecules that can’t be digested (broken down) into simpler substances
So
■ Small enough to diffuse across cell membranes into the cells
■ Eg. Glucose, Fructose, Galactose (𝐶6𝐻12𝑂6 )
○ Disaccharides (double sugars)
■ Made up of two molecules of monosaccharides that are chemically bonded together
■ Eg. Maltose, sucrose, lactose ( 𝐶12𝐻22𝑂11 )
● Polysaccharides
○ Complex carbohydrates made up of many monosaccharides chemically bonded together
○ Insoluble in water; not sweet
