A cells ability to process information from
their environment.
 Could be a physical stimulus.
 Could be a ligand.
 A chemical signal
 Molecule that binds
to a receptor.
 Cells must have a specific receptor that can detect the
signal.
 Once the signal activates its receptor , it sets off the Signal
Transduction Pathway
 A sequence of molecular events and chemical reactions
within a cell that leads to the cell’s response.
The ability of cells to sense and
respond to signals in the
environment.
Affect the same cell that releases them.
 Tumor cells reproduce uncontrollably because they
self-stimulate cell division by making their own
division signals.
Diffuse to and affect nearby cells.
Neurotransmitters made by a nerve cell
that diffuses to an adjacent cell and
stimulate it.
Requires direct contact
between the signaling
and the responding
cell, and usually
involves interaction
between signaling
molecules bound to the
surface of the two cells
Signals that travel
through the circulatory
system of animals or the
vascular system of plants
to reach receptors on
distant cells.
Chemical Signals do not always come from
within a multicellular organism, some come
from the external environment.
SIGNAL TRANSDUCTION PATHWAYS
Convert signals on a cell’s surface into cellular
responses
Are similar in microbes and mammals, suggesting
an early origin
3 Phases of Signal Transduction
EXTRACELLULAR
FLUID
1 Reception
Plasma membrane
CYTOPLASM
2 Transduction
3 Response
Receptor
Activation
of cellular
response
Relay molecules in a signal transduction pathway
Signal
molecule
Figure 11.5
STEP ONE - RECEPTION
Reception occurs when a signal
molecule (ligand) binds to a receptor
protein.
 Ligand
and receptor have a unique bonding
STEP TWO - TRANSDUCTION
Signal initiated by conformational change of receptor
protein
Signal is turned into a cellular response.
Signaling cascades relay signals to target
Multistep pathways can amplify a signal
 Second messengers involved
STEP THREE - RESPONSE
Cell signaling leads to regulation of
cytoplasmic activities or transcription
 Signaling pathways regulate a variety of
cellular activities
Involves an alteration in the 3D shape of a
protein as a result of the binding of another
molecule at a site other than the protein active
site.
https://www.youtube.com/watch?v=WAZXq
htduFw&spfreload=5
Intracellular Receptors
Located inside the cell.
https://www.youtube.com/watch?v=JQ
cFk7J_Tf4
Membrane Receptors
 Located on the cell surface
https://www.youtube.com/watch?v=FkkK5lTmBYQ