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This contains three main ideas:
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They are the smallest unit of life
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Cells store all the information they require for growth, development and
behaviour
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2 - Discuss the evidence for the cell theory
Cells are the Building Blocks of Structure in Living Things
All living things observed through microscopes have been found to be made up of cells,
proving that living things are made up of cells
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They can only reproduce at the
expense of the cell's metabolic machinery
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Cell Substructures: The lifespan of organelles has been found to be extremely short when
they attempt to function outside the cell
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All Cells are Formed from Pre-existing Cells
Pasteur's observations: He proved that the apparent 'spontaneous' generation of
microorganisms was in fact due to the presence of unnoticed cells
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A related discovery
was that spores of many microorganisms are found everywhere, but will only develop in
favourable conditions
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Research has also established the nature and roles of genes in the day-today control of cells and in the process of heredity
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Cells are the site of the necessary chemicals needed for life: The discovery of enzymes and
their machinery, which are used in the chemical processes with a cell
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The discovery of biochemical events with cells also proved
this
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Scientists
have shown that, because every cell contains organelles which are the locations of specific
chemical reactions, they are the place where all these necessary processes of life take place
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Metabolism - this includes the respiration and synthesis of ATP
Response - to any change in the environment
Homeostasis - the maintenance and regulation of internal cell conditions
Growth - when the cell increases in size and volume
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Reproduction - unicellular organisms are asexual, therefore they reproduce
through division to form a clone
Nutrition - this is either the synthesis of organic molecules or the absorption of
organic matter
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4 - Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria,
organelles and cells, using the appropriate SI unit
Relative Sizes
1 nm – Molecule
10 nm – Cell membrane
100 nm – Virus
1000 nm – Bacteria (1μm)
10000 nm – Organelles (10μm)
100000 nm – Cells (100μm)
1cm
1mm
1μm
1nm
10-2m
10-3m
10-6m
10-9m
centimetre
millimetre
micrometre
nanometre
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5 - Calculate the linear magnification of drawings and the actual size of specimens in
images of know magnification
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6 - Explain the importance of the surface area to volume ratio as a factor limiting cell
size
As the size of a structure increases, the surface area to volume ratio decreases
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As a result, larger organisms have a slower rate of exchange (diffusion/radiation)
with their outside surroundings
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All organisms need to
exchange substances such as food, waste, gases and heat with their surroundings
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For this reason, cells are very small so that they are able to exchange substances efficiently
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Multicellular organisms have properties that exceed the sum of the properties of its
constituents
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The
properties emerge as a result of the interaction of the parts
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It needs other things to give this to
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Differentiation - The cells can become specialised to perform their function
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The
expression of these genes will influence the shapes, functions and adaptations with that cell
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Specialisation in multicellular organisms is more efficient for organisms competing for a
specific resource
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9 - State that stem cells retain the capacity to divide and have the ability to
differentiate along different pathways
Stem cells can divide, however they have not yet expressed any of their genes so that they
might specialise in a particular function
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They can be obtained from a variety of places including blastocyte, or even the placenta
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Stem cells used for research are usually human embryonic stem cells, which come from
embryos only a few days old
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The techniques are controversial, thus there are international principles regarding this
work
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One of these possibilities
is with cystic fibrosis
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This therapy would
also eliminate the problem of tissue rejection in transplant surgery, as the cells are from
the patient
Stem cells also hold promise for the testing of new drugs
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Other cells
are already used in this way
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