Lecture 4 Outline (Ch. 9)
I. Cell Signaling Overview
II. Signal Transduction
III. General Cell Responses
IV. Reception in Detail
V. Transduction in Detail
VI. Exam Review
Cell Signaling = Signal Transduction
Signal Transduction – receiving a signal & relaying the response
Signal Transduction
Cell phone rings
1
Reception
You listen to
your friend
2
Transduction
You drive
somewhere
3 Response
Receptor
Relay molecules
Signaling
molecule
Response variable
Activation
of cellular
response
Sending the Signal
Reception – receptors for hydrophilic molecules
Signal called a ligand
Reception – receptors for hydrophobic molecules
Transduction – relay the signal
• Phosphorylation: adding a phosphate group
• Used to activate proteins already in the cell
Transduction – relay the signal
Signaling molecule
• hydrophilic signals
Receptor
Activated relay
molecule
Inactive
protein kinase
1
Receptor alerts
molecules inside the
cell = phosphorylation
Active
protein
kinase
1
Inactive
protein kinase
2
ATP
ADP
Pi
P
Active
protein
kinase
2
PP
Inactive
protein kinase
3
Pi
ATP
ADP
Active
protein
kinase
3
PP
Inactive
protein
P
ATP
P
ADP
Pi
PP
Active
protein
Cellular
response
Transduction – relay the signal
First messenger
Adenylyl
cyclase
G protein
G protein-coupled
receptor
GTP
ATP
• Or use second messengers
= small molecules inside cell
cAMP
Second
messenger
Protein
kinase A
• examples: cAMP, ATP, Ca++
Cellular responses
Response – cell does something
1 mm
Interdigital tissue
Response – ex. No death signal, cell lives
protein (active)
Inhibits activity
Mitochondrion
Receptor
for deathsignaling
molecule
Inactive
proteins
(a) No death signal
Response – ex. Death signal, cell undergoes apoptosis
Cell
forms
blebs
(inactive)
Deathsignaling
molecule
Active Active
Activation
cascade
(b) Death signal
Other
proteases
Nucleases
Signal transduction = reception, transduction, response
Growth factor
Reception
Receptor
Phosphorylation
cascade
Transduction
CYTOPLASM
Inactive
transcription
factor
Active
transcription
factor
P
Response
DNA
Gene
NUCLEUS
mRNA
Lecture 4 Summary
1. Cell Signaling Overview (Ch. 9)
Reception
Transduction
Response
2. Sending the signal (Ch. 9)
Contact, paracrine, endocrine, synaptic
Hydrophilic vs. hydrophobic ligands
3. Signal Reception (Ch. 9)
4. Transduction (Ch. 9)
Phosphorylation/dephosphorylation
Cascades/amplification
Second messengers
5. Cellular Response (Ch. 9)
Exam I Review
Actually write down info – I may collect some of this….
For each of the following images, discuss with your partner briefly
and agree what the image is showing.
THEN, each person write their own question about this topic –
avoid simple questions such as “what is this image” in favor of
concepts about the image.
THEN, exchange questions with your neighbor and solve/answer.
Discuss your answers and grade each other.
I may call on specific teams to provide examples of their questions
(remember, if I like them, they may appear on the test!)
Photosynthesis:
(Endergonic)
Active
protein
kinase
1
Inactive
protein kinase
2
ATP
ADP
PP
Pi
P
Active
protein
kinase
2
1
2
3