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CELL SPECIALIZATION
Chapter 7 Section 4
EQ: Why do cells in multicellular organisms
become specialized?
Some cells send signals

Most are chemical signals
◦ hormones
◦ neurotransmitters

Target cells receive the signal
◦ Have receptors either on outer side of
cell membrane or inside cell (if signal
can cross membrane)
Receiving Signals

Receptor proteins
◦ Bind only signals that match specific
shape of its binding site
◦ Once signal molecule binds to receptor
site  receptor protein changes shape
 which relays “message” to the
target cell
Responding to Signals

The cell may respond to a signal
by:
◦
◦
◦
◦
Changing its membrane permeability
Activating enzymes
Causing a second messenger to form
Second messenger is a molecule that
is generated when a specific signal
attaches to a receptor protein; it
causes a change in cell function
Neurotransmitter Serotonin
Animation
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CELL SPECIALIZATION
Stem Cells: type of cell that gives rise
to all types of cells in that organ
system
 During embryonic development, cells
not only increase in #, but also
undergo differentiation becoming
specialized in structure & function

Cell Differentiation
Cell Specialization

Columnar Cells

Cuboidal Cells

Squamous Cells

Neurons
Why do some cells become neurons
& others become red blood cells?
Why do some cells become neurons
& others become red blood cells?

Different genes are “turned on” so
specialization happens