MH: 85 – 91, 93 - 96
N: 77 - 79
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In a single-celled organism, 1 cell is capable
of every function needed to survive
In multicellular organisms, survival is
accomplished by groups of specialized cells
vs
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Atoms
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Molecules
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Organelles
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Cells
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Tissues
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Organs
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Body systems
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Organisms
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Your body has similar needs to that of a city:
◦ Transportation
◦ Energy
◦ Waste disposal, etc.
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Similar to people working in a city, specialized cells
have physical and chemical differences that allow
them to perform one job really well
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In general, specialized cells give rise to
similarly specialized cells
◦ eg. a lung cell divides to make 2 daughter lung cells
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But where did those first lung cells come
from?
And what about tissues that contain
numerous cell types, like blood?
Stem cells – cells that can divide and
differentiate into diverse specialized cell
types
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A stem cell’s ‘potential’ to differentiate is its
potency, and there are 3 levels:
◦ Totipotency
◦ Pluripotency
◦ Multipotency
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Some stem cells have the ability to
differentiate into ANY cell type (including
embryonic tissues)
these are called totipotent stem cells
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The only true totipotent stem cells exist in a
developing zygote
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Some stem cells have the ability to
differentiate into any ADULT cell
these are called pluripotent stem cells
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Pluripotent stem cells
come from
◦ developing embryos
◦ umbilical cord blood
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In 2006 scientists discovered that they could
induce normal body cells (skin, lung, etc.) to
become pluripotent
Induced pluripotent stem cell (iPSC) research
may be the future
Dr. Gurdon & Dr. Yamanaka
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Some stem cells have the ability to only
differentiate into related cell types (eg. blood)
these are called multipotent stem cells
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These are often referred
to as ‘blood stem cells’ or
‘skin stem cells’ because
they can only give rise to
cells of that specific line