Download Cells - P5 GE Science 2011

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Questions to think about…
What are the different
parts of a plant cell and
an animal cell and what
are their functions?
What forms the
basic unit of
life?
How is an animal
cell different from a
plant cell?
What are the different
types of cells?
How do cells
produce new cells?
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Cells
• All living things are made of
cells.
• A cell is the smallest unit of life
in the body.
• Most living things like people,
cows and trees are made up of
millions of cells.
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Cells
• We can look at cells
and study them with
the help of a powerful
microscope.
an optical microscope
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Cells
• Some living things are made of fewer cells,
like certain algae, mosses and anemones.
moss
anemone
algae
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Cells
• Some other living things are made up of only one
cell.
• These are single-cell organisms, such as
bacteria, yeast and paramecium.
• The cells can only be seen under a microscope.
paramecium
bacteria
yeast
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Different types of cells
• Plants are made up of
cells too.
• There are cells in all parts
of a plant – the leaves,
the stem, the roots.
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Different types of cells
• Some cells in a leaf make food
for the plant.
• These cells contain chlorophyll.
• Chlorophyll traps light energy
from the Sun to allow plants to
carry out photosynthesis.
• There are also cells that control
the size of the stoma.
stoma
cells in a leaf
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Different types of cells
• Some cells in the stem
transport food and water
within the plant.
• The xylem and phloem
tubes are made up of such
cells.
xylem
phloem
cells in a stem
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Non-living things
• Unlike living things, non-living things do
not have cells.
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Different types of cells
• What is inside a typical animal cell?
Nucleus
Cytoplasm
Cell
membrane
• In
Allboth
Surrounding
cellsplant
is made
the
andcytoplasm
up
animal
of a
jelly-like
is
cells,
a soft
there
and
substance
isthin
a nucleus
cell
called
the cytoplasm.
membrane.
found
in the cytoplasm.
• The nucleus
cytoplasm
cell
membrane
is a
allows
very
holds
substances
the
important
cytoplasm
part
such
of
inside
aascell.
food
it.
oxygen
to move
• and
It controls
also
controls
everything
substances
that
around
within
the
that go in
happens
inside
or out
the
ofcells.
acell.
cell.
• Many activities of the cells
take place in the cytoplasm
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Different types of cells
• What is inside a typical plant cell?
o
o
A plant cell has cytoplasm, a cell membrane, and
nucleus, just like the animal cell.
However, a plant cell has other parts that are not
found in an animal cell.
nucleus
cytoplasm
cell membrane
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Different types of cells
• What is inside a typical plant cell?
Sap wall
Chloroplast
Cell
•• A
fills
cavity
chloroplast
is athe
A liquid
plantwhich
cell has
a tiny
cell
in
the centre
of most
plant
green
structure
that
is
wall
outside
the
cell
cells.
found
in the cytoplasm of a
membrane.
• The
plantsap
cell.keeps the cell firm.
•• The
cell wall is
made up
Firm
cells helpcontain
the plant to
Chloroplasts
of
a stiff
material
thatdo
stand
upright
plants
chlorophyll,
aas
pigment
that
gives
a plant
cell system
its
not
have
a skeletal
to
traps
sunlight
for
provide
support.
shape.
photosynthesis.
•• Animal
cellsare
do
not
have
Cell
walls
not
found
Chloroplasts
are
not
such
cavities
in them.
present
in animal
cells.
in animal
cells.
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Different types of cells
• Cells come in different
shapes and sizes.
• Different types of cells
have different functions.
• In the human body, cells
work in groups, like those
in the heart and the brain.
• They form the organs in
the body.
a brain cell
heart muscle cells
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Different types of cells
• Other cells such as
red and white blood
cells travel within the
body to do their jobs.
red blood cells
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Producing new cells
• Our bodies increase in size as we
grow.
• This is due to an increase in the
number of cells in the body.
• Cells increase in number by dividing
themselves.
• The nucleus and cytoplasm of one cell
divide to produce two cells.
• The two new cells later divide into four
cells.
• These four cells can divide to form
more cells.
• This process is known as cell division.
• It takes place all the time to allow cells
to multiply.
cell division
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Producing new cells
• Single-cell organisms, such as paramecium, yeast and
bacteria, multiply by cell division.
• The new cells produced are identical to the original cell.
• Yeast multiplies by a special cell division method called
budding (see below).
o
o
In budding, a small bud grows from a yeast cell.
The bud slowly increases in size and then breaks away.
bud growing
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Producing new cells
• Cells do not live forever.
• Old cells die and new ones are produced to
replace them.
• This takes place in our bodies all the time.
• Our skin cells can live for 3 weeks while the cells
lining out intestines are replaced after 3 days.
• Some cells also divide to help repair damaged
parts of our bodies.
© 2009 Marshall Cavendish International (Singapore) Private Limited
© 2009 Marshall Cavendish International (Singapore) Private Limited