Transcript Higher Biology

National 5 Biology
Cell Structure
Mr G Davidson
Cellular Structure
• Cells are the living units from which
all organisms are made.
• Simple organisms have only one cell
and are unicellular, e.g. bacteria.
• Other organisms have many cells
working together and are
multicellular, e.g. humans.
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Animal Cell Structure
Cell membrane
Ribosome
Nucleus
Mitochondrion
Cytoplasm
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Animal Cell Structure
Cell Structure
Function
Nucleus
Controls cell activities and passes on
information to the next generation
Cytoplasm
Site of all biochemical reactions
Cell membrane
Controls what enters and leaves the cell
Mitochondrion
Site of aerobic respiration
Ribosomes
Site of protein synthesis
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Plant Cell Structure
Nucleus
Ribosome
Cell wall
Cell
membrane
Mitochondrion
Sap vacuole
Cytoplasm
Chloroplast
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Plant Cell Structure
As well as the same structures found in animal cells,
the following structures are also found in plant cells only.
Cell Structure
Function
Chloroplast
Contains chlorophyll which traps light
energy to be used in photosynthesis
Cell wall
Made of cellulose and supports the
structure of the cell
Vacuole
Stores water and solutes as a
solution called “cell sap”
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Fungal Cell
Cell membrane
Mitochondrion
Cell wall
Nucleus
Vacuole
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Cytoplasm
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Fungal Cell Structure
• An example of a unicellular fungus is
yeast.
• It has structures in common with
both animal and plant cells.
• These structures carry out the same
functions.
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Bacterial Cell
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Bacterial Cell Structure
• Bacterial cells can be all different shapes.
• The structures within the bacterial cell are much
the same as animal cells.
• The main difference is a lack of a nucleus.
• Bacterial cells have plasmids which are circular
rings of DNA as well as a large circular DNA.
• The cell wall is different from a plant cell wall in
that it is kind of slimy.
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Cell Sizes
• Cells cannot be seen without the aid of
a microscope.
• They are so small that we used units
called micrometres(μm) or microns to
measure them.
• There are 1000 microns in 1 millimetre.
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Cell Sizes
• We can estimate the sizes of cells by
knowing the diameter of the field of
view.
• e.g. if the field of view is 2mm which is
2000μm, and there are 8 cells
stretching from one side to the other,
then each cell must be 250μm.
(2000/8)
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Cell sizes
Field of View
• This field of view is
1mm.
• Estimate the size of
each cell.
• Answer – 62.5μm
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Cell Sizes
• We can magnify the size of the cells using the
lenses on the microscope.
• Total magnification = eyepiece x objective
• e.g. if the objective lens is x20 and the
eyepiece is x10, then the total magnification
will be x200.
• If we increase the magnification of the
microscope the number of cells we see in the
field of view decreases.
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