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

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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?

Different genes are “turned on” so specialization happens