Topic 8: Signal transduction

Signal transduction “connects” the inside of cells with their “external environment” (which may be inside an organism/ inside a tissue). So, what might signals tell cells to do?

-change gene expression to respond

-to die

-alter metabolism

-adjust hormones (or other signals) to produce

-differentiate-change to “become what cell is intended to be”

-to stay alive

-divide

Extracellular signals are essential for ( ), lack of signaling may result in ( ), different signals result in ( )

physiology

apoptosis

different responses 

look at slide 5

okay

Important concept: Cells have ( ) to perceive + respond to environmental/external (to the cell) signals

multiple mechanisms

Extracellular signals activate ( ), a typical signal transduction pathway includes the following components.

signal transduction pathways

extracellular signal molecule

receptor protein

intracellular signaling proteins

effector proteins

look at slide 7

okay

ligand binding sites are determined by ( ), brings important amino acids “together” so they can ( ) with ligand 

protein structure 

interact 

signal transduction can result in ( ) or ( ) in cell ( )

acute (sudden,temporary)

longer-term

physiology

Extracellular signals are classified based on their site of action, these include?

cell-cell contact dependent

paracrine

endocrine

synaptic

( )- especially important for development, recognition of neighboring cell type

-ex: immune response; cell R7 of Drosophila eye development

cell-cell contact dependent 

( )

-signal molecule released into extracellular fluid by signaling cell

-signal detected by nearby target cells

paracrine

( )-( ) system produces hormones released into blood stream- so can travel over long distances to target cells

endocrine

endocrine

( )

-nerve cells allow long distance communication through neurons with long axons

-also connect many linked cells and transmission of signals to cells close by 

synaptic 

more general characteristics of signaling pathways

1) signals can trigger different responses in different cell types

2) receptors may be on cell surface or intracellular or even intraorganellar

signals can trigger different ( ) in different cell types

responses

Receptors can be on the ( ) or ( )- including in the ( ) or on ( ) or even inside ( )

cell surface 

intracellular 

cytoplasm

organelles 

many important signal molecules bind ( ) receptors: these have ( ) differences but all ( )

intracellular

structural

alter gene expression

signaling receptors may be intraorganellar, on ( ) of organelles, inside ( )

membrane

organelles (e.g. inside the nucleus)

an example of an intraorganellar signal receptor

nuclear receptor, special type- ligand binding and DNA binding (activator) receptor 

What are the three main classes of cell surface signal receptors?

1) ion channel- coupled receptors

2) G-protein-coupled receptors (GPCRs)

3) Enzyme-coupled receptors