National 4 Unit 1
Cell Biology
Revision Notes
Key Area 1 – Cell division and its role in growth and
repair
Cell division is essential to allow organisms to grow and repair
damaged parts, e.g. cuts, broken bones.
During cell division, the parent cell divides to produce two identical
cells, which contain the same number of chromosomes in their
nuclei as the parent cell. Cancer as uncontrolled cell division.
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Key Area 2 – DNA, genes and chromosomes
Genes are located on chromosomes in the nucleus.
Genes are made of DNA which carries the instructions to make
proteins.
Each individual’s DNA is unique. Genes are passed on from parents
to offspring.
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Key Area 3 & 8 – Therapeutic use of cells &
Controversial biological procedures
Insulin, human growth hormone, Factor VIII or other proteins can
be made via genetic engineering.
Stem Cells:
It is an unspecialised cell that can differentiate to into a specialised
cell, e.g. a red blood cell, nerve cell. Stem cells are found in
embryos, the umbilical cord and adults have them in places like their
bone marrow.
Embryonic Stem cells
Arguments for:
• Embryonic stem cells could hold potential cures for spinal cord
injuries, multiple sclerosis, diabetes, Parkinson's disease,
cancer, Alzheimer's disease, heart disease, hundreds of rare
immune system and genetic disorders and much more.
• Scientists see a huge value in the use of embryonic stem cell
research to understand human development and the growth
and treatment of diseases.
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Arguments against:
• Some people believe that life begins at conception, and that
destruction of this pre-born life is morally unacceptable even
to save or reduce suffering in existing human life.
• Many also believe that not enough attention is given to look
into adult and/or umbilical cord blood stem cells, which have
already been used to successfully cure many diseases.
Saviour Siblings:
A child who is born to provide an organ or cell transplant to a
sibling that is affected with a fatal disease, such as cancer or blood
conditions. The saviour sibling is conceived through in vitro
fertilization (IVF).
Human Cloning:
The creation of a genetically identical copy of a human but it
does not refer to multiple births. The ethics of cloning is an
extremely controversial issue.
Artificial Organs:
Using embryo, umbilical cord blood or adult stems cells to create
an organ.
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Key Area 4 – Properties of enzymes and use in industries
Enzymes:
 Are found in living cells.
 Are specific – only one enzyme will work the one substrate,
e.g. amylase will only break down starch.
 Can speed up chemical reactions in cells.
 Are unchanged by the reaction.
 Can build-up and break-down molecules.
Enzymes can be used in a range of biotechnology industries:
 Rennet found in cheese.
 Biological washing powders.
Key Area 5 – Properties of microorganisms and use in
industries
Microorganisms:
 Can grow rapidly.
 Using them allows food to last longer (e.g. yoghurt lasts longer
than milk)
 Can make a wide range of products.
Examples of how some cells work and are used in industrial
processes:
 Yeast in baking, brewing (beer making) and wine making.
 Bacteria for yoghurt and biofuels production.
 Production of cheese.
Beer & Wine
Bread
Yoghurt
Biofuels
Antibiotics
Yeast
Bacteria
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Key Area 6 – Photosynthesis — limiting factors
Light energy
Carbon dioxide + Water
Glucose + Oxygen
Chlorophyll
If any of the requirements for photosynthesis are low or missing,
the photosynthesis rate is limited.
Limiting factors for photosynthesis are:
 Light
 Carbon dioxide
 A suitable temperature
 (Water)
Light is the limiting
factor.
Another factor is limiting
the rate of
photosynthesis e.g.
Carbon dioxide.
By overcoming these limitations, faster growth rates can be
achieved.
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Key Area 7 – Factors affecting respiration
Respiration is used to release energy for use in cells. Oxygen may or
may not be used in both yeast and animal cells.
When oxygen is available, yeast, plant and animal cells use glucose
to produce carbon dioxide and water.
Glucose + Oxygen
Energy + Carbon dioxide + Water
Without oxygen, yeast and plant cells use glucose to produce alcohol
and carbon dioxide.
Glucose
A little Energy + Carbon dioxide + Alcohol
Without oxygen, animal cells use glucose to produce lactic acid
Glucose
A little Energy + Lactic Acid
More energy is released per molecule of glucose when oxygen is
present.
The process is enzyme controlled in all cases and so is affected by
temperature.
The mass of glucose and/or volume of oxygen will affect the rate
of the respiration.
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