Lecture # 5 Date
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Transcript Lecture # 5 Date
Chapter 11 – Cell
Communication
Signal-transduction pathway
Signal on a cell’s surface is converted into a specific cellular response
Local signaling (short distance):
Paracrine (growth factors)
Synaptic (neurotransmitters)
Long distance: hormones
Signal Transduction Pathway
Cell Signaling
Reception – target cell detection of a signal molecule, is detected
when signal molecule binds to receptors surface
Transduction – converts the signal to a form that can bring about a
cellular response; can be a single-step or a series of changes
(signal transduction pathway)
Response – triggering of a specific cellular response
Cell Signalling
Membrane Receptors
G-protein linked
receptors
GDP bound =
inactive
GTP bound = active
Receptor is active
when signal is
attached
Enzyme activated,
GTP GDP
Membrane Receptors
Tyrosine kinases
Kinases –
phosphorylate
Can trigger multiple
cellular responses
Signal binding
causes dimer
formation
Adds phosphates
Activates relay
proteins to elicit
cellular response
Membrane
Receptors
Ion channel receptors
When signal is absent,
gate closed
Signal (ligand) binds –
gate opens, ions move in,
elicit cellular response
Signal detaches closing
the gate
Transduction Pathways
Phosphorylation
cascade
Adding P from
ATP to activate
proteins
Uses protein
kinases
Approx. 2% of
our genes
thought to code
for protein
kinases
Transduction Pathways
Second messengers
Non-protein pathways
Example – cAMP (cyclic
adenosine
monophosphate)
Includes a g-proteinlinked receptor
The cAMP activates
another protein (usually
kinase)
Animation
Response
Cytoplasmic response
Regulate the activity
of enzymes
Example breakdown
of glycogen into
glucose-1-phosphate
Also an example of
signal amplification
Animation
Response
Nuclear response
Regulate the
synthesis of proteins
Example:
transcription factors
animation