1. Cell Communication
REVIEW

2. Cell Signaling cells communicate by: Direct Contact
VERY short distances -
Examples:
gap junctions
plasmodesmata

3. cells communicate by:
2. Secreting Local Regulators short distances (paracrine signaling) Examples: - growth factors - neurotransmitters moving across a synapse

4. cells communicate by:
3. Long Distance Examples: - hormones traveling through bloodstream (endocrine signaling)

5. 3 Stages of Cell Signaling:
Reception
Transduction
Response

6. Reception signal molecule is detected coming from outside the cell
Signal moelcule/ligand/protein
Protein
Receptor
Initiates
Transduction
Binds to / activates
Changes shape / activates
Protein Receptor
Ligand

7. Transduction
signal is converted to a form that can bring about a cellular response (often involves amplification)
Amplification

8. Response Cell responds to the signal molecule
Ex: apoptosis, cell division, gene transcription, protein activation, cell growth, etc.
- Response can target the nucleus or the cytoplasm

9. 1. Reception 2 types of Receptors:
1) Plasma Membrane Surface Protein Receptors
Bind hydrophilic / water-soluble ligands / proteins
Allow for facilitated diffusion
G-Protein Coupled Receptors
Tyrosine Kinases
Ligand-Gated Ion Channels

10. G-Protein Coupled Receptors
Moves along the membrane
Binds to
Changes shape
Ligand
Protein Receptor
G-protein Activated
Enzyme Activated
Protein receptor is highly specific to the shape of the ligand!
Activated enzyme changes shape and triggers next step in cell response
G protein is a molecular switch.
Inactive/off when GDP is bound
Active/on when GTP is bound

11. Tyrosine Kinases Tyrosine Kinase Receptor acts like an enzyme Binds to
Amplification of cellular transduction & response
Goes through a shape change & activates
Tyrosine Kinase Receptor acts like an enzyme
Binds to
Ligand
Many relay proteins at once

12. Ligand-Gated Ion Channels
Ex: Neurotransmitters
Ligand-gated ion channel receptor
(=gate)
Neurons are an example of a voltage-gated channel
Movement of ions (Ca++, Na+, Cl-, etc) to move in or out of the cell to activate it in some way
Changes shape & allows
Binds to & opens
Ligand
Gate closes when ligand dissociates

13. 1. Reception 2 types of Receptors: 2) Intracellular Receptors
Allows hydrophobic , small, or lipid-soluble molecules to pass through the receptor/membrane
Examples: Testosterone, Nitric Oxide (NO)

14. 2. Transduction Cascades: a series of relay molecules
Help AMPLIFY a signal to cause a greater cellular response
Often involve Protein kinases (turn signal on)
May involve Protein phosphatases (turn signal off)
Ex: Phosphorylation cascade

16. 2. Transduction Second Messengers
small, non-protein molecules or ions that can relay a signal inside cell
Once activated, cause a phosphorylation cascade
Examples: cAMP, Ca2+

17. 3. Response If the signal’s target response is in the: CYTOPLASM 
regulates activity of cytoplasmic proteins and/or enzymes
Usually a quick response, but short lived

18. AP Test Prep Book
Review pp.
62-65
236
253

19. Sample Test
P. 335
DO NOT TURN TO THE ANSWERS IN THE BACK