1. Cell Communication
Big Idea 3: Living systems store, retrieve, transmit, and respond to info essential to life processes.

2. Essential Knowledge
3D1: Cell communication processes share common features that reflect evolutionary history.
3D2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling.
3D3: Signal transduction pathways link signal reception with cellular response.
3D4: Changes in signal transduction pathways can alter cellular responses.

3. Simple Communication Turn cell activity on Turn cell activity off
Stimulatory
Turn cell activity on
Inhibitory
Turn cell activity off

4. Origin of Cell Signaling
Single celled orgs to “communicate” w/ each other
Ex: when it gets crowded bacteria can send signals to shut off reproduction (quorum sensing)
Conserved through evolution

6. Coordinate cellular actions
Why Talk?
Coordinate cellular actions
Ex: when frightened you release epinephrine, which triggers mobilization of glucose and other energy resources
Fight or flight

7. Distance of Communication
1) Direct contact
2) Local communication
3) Long distance

8. Example of Direct Contact
Plant cells walls have plasmodesmata  allow material to be transported b/t cells.

9. Example of Direct Contact
Antigen-presenting White blood cell directly contacts helper T cells
Activates immune responses

10. Example of Local Regulation
Neurotransmitters (chem messengeres in b/t neurons)
Serotonin, dopamine common nm’s.

11. Example of Long Distance Signaling
Hormones
Released from endocrine glands and travel in blood
Affect target cells

13. Highly specific proteins
Step 1: Reception
Signal molecule (aka ligand) binds to a receptor protein  change shape
Highly specific proteins

14. Type 1 Receptor: G protein
G protein acts as an on/off switch: If GDP is bound to G protein  G protein is inactive

15. http://highered. mcgraw-hill

16. G Proteins and Medicine
Diabetes, blindness, allergies, depression and some cancers are believed to come from dysfunctional G proteins
Up to 60% of medicines used influence G-Protein Pathways

17. Type 2: Receptor Tyrosine Kinases
Membrane receptors that attach phosphates to tyrosines (a.acids)
Tyrosine = amino acid!

19. Type 3: Ligand-gated ion channel
Receptor acts as a gate when receptor changes shape

20. Intracellular Receptors
Small/hydrophobic chemical messengers can cross membrane and activate receptors in cytoplasm Ex: hormones!

21. Hormone (testosterone) Plasma membrane Receptor protein DNA NUCLEUS
Fig
Hormone
(testosterone)
EXTRACELLULAR
FLUID
Plasma
membrane
Receptor
protein
DNA
Figure 11.8 Steroid hormone interacting with an intracellular receptor
NUCLEUS
CYTOPLASM

22. Hormone (testosterone) Plasma membrane Receptor protein Hormone-
Fig
Hormone
(testosterone)
EXTRACELLULAR
FLUID
Plasma
membrane
Receptor
protein
Hormone-
receptor
complex
DNA
Figure 11.8 Steroid hormone interacting with an intracellular receptor
NUCLEUS
CYTOPLASM

23. Hormone (testosterone) Plasma membrane Receptor protein Hormone-
Fig
Hormone
(testosterone)
EXTRACELLULAR
FLUID
Plasma
membrane
Receptor
protein
Hormone-
receptor
complex
DNA
Figure 11.8 Steroid hormone interacting with an intracellular receptor
NUCLEUS
CYTOPLASM

24. Hormone (testosterone) Plasma membrane Receptor protein Hormone-
Fig
Hormone
(testosterone)
EXTRACELLULAR
FLUID
Plasma
membrane
Receptor
protein
Hormone-
receptor
complex
DNA
Figure 11.8 Steroid hormone interacting with an intracellular receptor
mRNA
NUCLEUS
CYTOPLASM

25. Hormone (testosterone) Plasma membrane Receptor protein Hormone-
Fig
Hormone
(testosterone)
EXTRACELLULAR
FLUID
Plasma
membrane
Receptor
protein
Hormone-
receptor
complex
DNA
Figure 11.8 Steroid hormone interacting with an intracellular receptor
mRNA
NUCLEUS
New protein
CYTOPLASM

26. Relayers are mainly proteins
Step 2: Transduction
Multiple steps
Can amplify a signal!
Relayers are mainly proteins
Domino effect!

27. Protein Phosphorylation
Signal passed by a protein phosphorylations
Protein kinases transfer PO4’s from ATP to protein (phosphorylation)

28. Phosphorylation cascade
Fig. 11-9
Signaling molecule
Receptor
Activated relay
molecule
Inactive
protein kinase 1
Active
protein
kinase 1
Inactive
protein kinase 2
ATP
Phosphorylation cascade
ADP
Active
protein
kinase 2 P PP P i
Figure 11.9 A phosphorylation cascade
Inactive
protein kinase 3
ATP
ADP
Active
protein
kinase 3 P PP P i
Inactive
protein
ATP
ADP P
Active
protein
Cellular
response PP P i

29. 2nd messengers: transfer messages in cytoplasm. Ex: cAMP
Second Messengers
1st messenger: ligand
2nd messengers: transfer messages in cytoplasm. Ex: cAMP

30. Cyclic AMP (cAMP): most widely used 2nd messenger
Adenylyl cyclase: enzyme in plasma membrane, converts ATP to cAMP in response to an extracellular signal

31. Fig. 11-10 Adenylyl cyclase Phosphodiesterase Pyrophosphate P P ATP
cAMP
AMP
Figure Cyclic AMP

32. First messenger Adenylyl cyclase G protein GTP G protein-coupled
Fig
First messenger
Adenylyl
cyclase
G protein
G protein-coupled
receptor
GTP
ATP
Second
messenger
cAMP
Figure cAMP as second messenger in a G-protein-signaling pathway
Protein
kinase A
Cellular responses

33. Step 3: Response AKA: “output response”
Usually activates transcription to make a protein.
Figure Nuclear responses to a signal: the activation of a specific gene by a growth factor

34. Importance of Cell Signaling
Diseases result from incorrect signaling
Drugs often target signaling mechanisms
Poisons and pesticides often target signaling pathways

35. Mr. Anderson Cell Signaling