IGCSE EDEXCEL BIOLOGY REVISION WORKSHEET
life processes
Characteristics of living organisms: (MRS.C.GREN)
M - movement G - growth
R - respiration R - reproduction
S - sensitivity (respond to stimuli) E - excretion
C - control N - nutrition
Animal Cell: Plant cell:
Nucleus: controls all cell activities, contains genetic material
Mitochondria: releases energy from respiration
Ribosome: where proteins are assembled
Cell membrane: a thin layer on the surface of the cell, it forms a boundary between the cytoplasm
and the outside. However, some particles can still pass into the cell, and pass out. It is selectively
permeable and chooses/controls the movement of substances.
Cytoplasm: the living material that makes up the cell
Cell wall: a layer of non-living material found outside of the cell member of plant cells, made mainly of
a carbohydrate called cellulose, it is a tough material that helps the cell keep its shape.It is freely
permeable. Not present in animal cells.
Vacuole: it is a permanent feature, filled with a watery liquid called cell sap (dissolved sugars, mineral
ions and other solutes). Not present in animal cells.
Chloroplast: absorbs light energy to make food in the process of photosynthesis, contains a green
pigment called chlorophyll. Not present in animal cells.
Metabolism - the sum of all chemical reactions in an organism
Diffusion - it is the net movement of particles from a region of higher concentration to a region of
lower concentration. Down a concentration gradient due to random movement
it is a passive process, it happens on its own.
Factors affecting diffusion:
• temperature • concentration gradient • surface area
• distance • size and mass of particles
Osmosis - it is the 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. Down a concentration gradient
Active transport - it is the movement of particles through a cell membrane from a region of lower
concentration to a region of higher concentration using energy from respiration
,particles move against (up) the concentration gradient
Special proteins found in the cell membrane called protein pumps help move (pump) particles across
a membrane using energy from ATP.
Anabolic reaction - making large molecules Catabolic reaction - breaking large molecules
from smaller molecules into smaller molecule
Enzymes - proteins that function as
biological catalysts, they are a
substance that increases the rate
of a chemical reaction and is not changed
by the reaction.
How enzymes work:
• the active site is complementary to the shape of the substrate
• each enzyme only reacts with a specific substrate
• this is known as the lock and key model
Factors affecting enzyme activity:
• temperature • enzyme concentration
• pH levels • substrate concentration
• surface area
Optimum - different enzymes have different optimums. All enzymes work best/fastest at only one
particular temperature and pH - this is the optimum.
What happens if the temperature/pH passes the optimum:
- the shape of the enzyme will change irreversibly
- it affects the shape of the active site, the enzyme will no longer work
- the enzyme is denatured (permanently)
- they can’t catalyse reactions anymore, and enzyme activity (rate of reaction) decreases
How does temperature affect enzymes:
the rise in temperature increases the rate of reaction (enzyme activity)
higher temperature gives more kinetic energy, enzymes move faster, and they collide more often,
more successful collisions means that more enzymes will be occupied, and reactions will take place
more frequently.
Respiration - a chemical reaction that happens in all living cells, it breaks down food molecules to
release the stored energy from glucose that they contain to carry out processes needed for life.
Aerobic respiration- the chemical reaction in cells that uses oxygen to break down nutrient
molecules to release energy.
glucose + oxygen —> water + carbon dioxide
𝐶6𝐻12𝑂6 + 6𝑂2 →6𝐻2𝑂 + 6𝐶𝑂2
,Anaerobic respiration - the chemical reaction in cells that break down nutrient molecules to release
energy without oxygen
Yeast: Humans:
Yeast can do both aerobic and anaerobic When oxygen demand exceeds what our body
respiration depending on if oxygen is can deliver, anaerobic respiration will occur:
available. Anaerobic respiration in yeast: Glucose → lactic acid/lactate
Glucose → ethanol + carbon dioxide
𝐶6𝐻12𝑂6→ 2𝐶2𝐻5𝑂𝐻 + 2𝐶𝑂2
Oxygen debt:
When exercising vigorously your muscles are overworked and will respire anaerobically
the lactate level will rise during anaerobic respiration.
After exercise, the volume of oxygen that is needed to completely oxidise/breakdown the lactate built
up in the body is called the oxygen debt
How do we use energy as ATP in our bodies:
• muscle contraction • transmission of nerve impulses (move,
• protein synthesis (growth and repair) senses)
• cell division (reproduction) • maintain a constant body temperature (37°C)
• active transport
Experiment: investigate the effect of temperature on enzyme activity
Equipment:
• Test tubes • Iodine solution
• Pipette • Amylase
• Starch solution • Water bath (10°C, 20 - 25°, 30 - 40°C)
- Pour amylase into starch solution, shake gently
- Measure the time taken for blue-black colour to disappear, become colourless
Results:
At 40° the reaction happened the fastest
Experiment: investigate the effect of pH on enzyme activity
Equipment:
• Test tubes • Potato juice
• Measuring cylinder • soap
• Buffer solution (pH 5, 6, 7, 8)
- Add HCL and buffer solution to the potato juice, mix gently
- Measure time for bubbles to reach the top of test tube
Results:
The highest pH (pH 8) produced the highest foam
Experiment: investigate the effect of oxygen on living organisms
The soda-lime is used to absorb CO2 so we
only measure the oxygen, and the gauze
keeps them separated.
the oil will move to the left as the organism
uses oxygen
Cell division:
Multicellular organisms begin life as a single
fertilised egg cell called a zygote. It then divides
over and over again by mitosis.
, Differentiation:
- as the developing embryo grows, cells become specialised to carry out particular roles, it is
controlled by genes
- all cells have the same genes, some must be switched on, and some switched off
Stem cell:
a cell that has the ability to divide endlessly while remaining undifferentiated
it will eventually divide into two cells, one will be a stem cell, one will be a differentiated (specialised)
cell (e.g - nerve, muscle, red blood cells)
• embryonic stem cells (ESC): • adult stem cells
- it is found in the embryo - found in children and adults
- it can differentiate into any type of cell - can differentiate into several different
types of cells (but not all cell types)
Stem cells: e.g - hemopoietic (blood) stem cells found in
We can use embryonic stem cells to treat the bone marrow can only differentiate into
many diseases. stem cells could be used to blood cells.
repair damaged nerve tissue.
We can also use adult stem cells to treat
diseases such as leukaemia.
- Some people are against stem cell research, they think extracting stem cells from an embryo
is destroying its life. Also, people think that when the stem cells are in the lab they might catch
a bacterial infection and then make the patients even sicker.
life processes
Characteristics of living organisms: (MRS.C.GREN)
M - movement G - growth
R - respiration R - reproduction
S - sensitivity (respond to stimuli) E - excretion
C - control N - nutrition
Animal Cell: Plant cell:
Nucleus: controls all cell activities, contains genetic material
Mitochondria: releases energy from respiration
Ribosome: where proteins are assembled
Cell membrane: a thin layer on the surface of the cell, it forms a boundary between the cytoplasm
and the outside. However, some particles can still pass into the cell, and pass out. It is selectively
permeable and chooses/controls the movement of substances.
Cytoplasm: the living material that makes up the cell
Cell wall: a layer of non-living material found outside of the cell member of plant cells, made mainly of
a carbohydrate called cellulose, it is a tough material that helps the cell keep its shape.It is freely
permeable. Not present in animal cells.
Vacuole: it is a permanent feature, filled with a watery liquid called cell sap (dissolved sugars, mineral
ions and other solutes). Not present in animal cells.
Chloroplast: absorbs light energy to make food in the process of photosynthesis, contains a green
pigment called chlorophyll. Not present in animal cells.
Metabolism - the sum of all chemical reactions in an organism
Diffusion - it is the net movement of particles from a region of higher concentration to a region of
lower concentration. Down a concentration gradient due to random movement
it is a passive process, it happens on its own.
Factors affecting diffusion:
• temperature • concentration gradient • surface area
• distance • size and mass of particles
Osmosis - it is the 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. Down a concentration gradient
Active transport - it is the movement of particles through a cell membrane from a region of lower
concentration to a region of higher concentration using energy from respiration
,particles move against (up) the concentration gradient
Special proteins found in the cell membrane called protein pumps help move (pump) particles across
a membrane using energy from ATP.
Anabolic reaction - making large molecules Catabolic reaction - breaking large molecules
from smaller molecules into smaller molecule
Enzymes - proteins that function as
biological catalysts, they are a
substance that increases the rate
of a chemical reaction and is not changed
by the reaction.
How enzymes work:
• the active site is complementary to the shape of the substrate
• each enzyme only reacts with a specific substrate
• this is known as the lock and key model
Factors affecting enzyme activity:
• temperature • enzyme concentration
• pH levels • substrate concentration
• surface area
Optimum - different enzymes have different optimums. All enzymes work best/fastest at only one
particular temperature and pH - this is the optimum.
What happens if the temperature/pH passes the optimum:
- the shape of the enzyme will change irreversibly
- it affects the shape of the active site, the enzyme will no longer work
- the enzyme is denatured (permanently)
- they can’t catalyse reactions anymore, and enzyme activity (rate of reaction) decreases
How does temperature affect enzymes:
the rise in temperature increases the rate of reaction (enzyme activity)
higher temperature gives more kinetic energy, enzymes move faster, and they collide more often,
more successful collisions means that more enzymes will be occupied, and reactions will take place
more frequently.
Respiration - a chemical reaction that happens in all living cells, it breaks down food molecules to
release the stored energy from glucose that they contain to carry out processes needed for life.
Aerobic respiration- the chemical reaction in cells that uses oxygen to break down nutrient
molecules to release energy.
glucose + oxygen —> water + carbon dioxide
𝐶6𝐻12𝑂6 + 6𝑂2 →6𝐻2𝑂 + 6𝐶𝑂2
,Anaerobic respiration - the chemical reaction in cells that break down nutrient molecules to release
energy without oxygen
Yeast: Humans:
Yeast can do both aerobic and anaerobic When oxygen demand exceeds what our body
respiration depending on if oxygen is can deliver, anaerobic respiration will occur:
available. Anaerobic respiration in yeast: Glucose → lactic acid/lactate
Glucose → ethanol + carbon dioxide
𝐶6𝐻12𝑂6→ 2𝐶2𝐻5𝑂𝐻 + 2𝐶𝑂2
Oxygen debt:
When exercising vigorously your muscles are overworked and will respire anaerobically
the lactate level will rise during anaerobic respiration.
After exercise, the volume of oxygen that is needed to completely oxidise/breakdown the lactate built
up in the body is called the oxygen debt
How do we use energy as ATP in our bodies:
• muscle contraction • transmission of nerve impulses (move,
• protein synthesis (growth and repair) senses)
• cell division (reproduction) • maintain a constant body temperature (37°C)
• active transport
Experiment: investigate the effect of temperature on enzyme activity
Equipment:
• Test tubes • Iodine solution
• Pipette • Amylase
• Starch solution • Water bath (10°C, 20 - 25°, 30 - 40°C)
- Pour amylase into starch solution, shake gently
- Measure the time taken for blue-black colour to disappear, become colourless
Results:
At 40° the reaction happened the fastest
Experiment: investigate the effect of pH on enzyme activity
Equipment:
• Test tubes • Potato juice
• Measuring cylinder • soap
• Buffer solution (pH 5, 6, 7, 8)
- Add HCL and buffer solution to the potato juice, mix gently
- Measure time for bubbles to reach the top of test tube
Results:
The highest pH (pH 8) produced the highest foam
Experiment: investigate the effect of oxygen on living organisms
The soda-lime is used to absorb CO2 so we
only measure the oxygen, and the gauze
keeps them separated.
the oil will move to the left as the organism
uses oxygen
Cell division:
Multicellular organisms begin life as a single
fertilised egg cell called a zygote. It then divides
over and over again by mitosis.
, Differentiation:
- as the developing embryo grows, cells become specialised to carry out particular roles, it is
controlled by genes
- all cells have the same genes, some must be switched on, and some switched off
Stem cell:
a cell that has the ability to divide endlessly while remaining undifferentiated
it will eventually divide into two cells, one will be a stem cell, one will be a differentiated (specialised)
cell (e.g - nerve, muscle, red blood cells)
• embryonic stem cells (ESC): • adult stem cells
- it is found in the embryo - found in children and adults
- it can differentiate into any type of cell - can differentiate into several different
types of cells (but not all cell types)
Stem cells: e.g - hemopoietic (blood) stem cells found in
We can use embryonic stem cells to treat the bone marrow can only differentiate into
many diseases. stem cells could be used to blood cells.
repair damaged nerve tissue.
We can also use adult stem cells to treat
diseases such as leukaemia.
- Some people are against stem cell research, they think extracting stem cells from an embryo
is destroying its life. Also, people think that when the stem cells are in the lab they might catch
a bacterial infection and then make the patients even sicker.
