Download - Pathways of Communication
Pathways of Communication
TED Video: Bacteria Communicate?
TED Video
Cell to Cell Interactions
Explain the following statement:
The sum is greater than the parts.
Who speaks?•Cells in constant communication
Unicellular OR Multicellular
With other organisms:• Cooperation• Competition
With other cells:• Cooperation• Successful
survival
Making the connections..•Cells excrete layer surround membrane
•The ECM! (extracellular matrix)▫Aids in:
Structure Protection
Filaments resist TENSION
Ground material resists COMPRESSION
ECM in plants•Primary Cell Wall – initial fiber
composite (cellulose microfibrils filled with pectin)
•Secondary Cell Wall – secreted by some plants▫Between membrane & 1º cell wall▫[High] of lignin (sturdy)
• Layer of pectins between cell walls(or membranes)
• “glues” cells• Degradation = Cell
separation
ECM in animals•Proteins NOT polysaccharides•Collagen = pliability•Amt varies
▫# surrounding cells▫Cell function (Ex: elastin in lungs)
•Structural properties: integral proteins bind to ECM proteins▫adjacent cells can bind at common
connections in ECM = increased stability
Predict! What would happen if ECM-cell
connection was lost? Can you think of an example?
•Cells migrate•Ex: malignant cancer
Reinforcement team in the Middle Lamella2 types of reinforcers:1. Tight Junctions – “quilting” formed by
connecting proteins in adjacent cells▫ Create water tight seal▫ Separate solutions (ie. Stomach
fluid/blood)▫ Dynamic
Tight Junctions
2. Desmosomes – connections between cytoskeletons of adjacent cells; “bolt” cells
**Cells Selectively Adhere**
•Proteins involved in cell binding – cadherins
cell specificity
Like cells aggregate
Cellular connections…
Mechanisms of Communication
the method behind cell “talking” near & far
Close communication in PLANTS!!!•Plasmodesmata – gaps in cell wall,
continuous cell membrane & plasma▫Smooth ER runs through
▫Regulated by proteins
How are these different from plasmodesmata?
•gap junctions – holes in ECM and membrane specialized proteins admit:
H2O aa’s sugar nucleotide
Close communication in ANIMALS!!!
Coordinate reactions (Ex: muscle contractions; heartbeats)
Fig. 11-4Plasma membranes
Gap junctionsbetween animal
cells(a) Cell junctions
Plasmodesmatabetween plant
cells
(b) Cell-cell recognition
Distant communication: 4 STEPS!1. Receive
2. Process
3. Respond
4. Terminate
1. RECEIVE•Signals are chemical “language”
(hormones)•Bind/Ligand to receptors (intra- OR
extracellular)
Characteristics:1.Cell specific2.Dynamic – overstimulation =
adaptation3.Potential blockage
•Upon receipt, response initiation begins•2 types:1. Direct
hormone enters
binds to receptor
complex enters nucleus
binds to DNA
directs gene expression
1. PROCESS
2. Indirecthormone binds to receptor
signal transduction begins
G-proteins
Receptor protein kinases
Both Pathways Result in: 1. Conversion of extracellular signal to intracellular
message2. Amplification of a message many times over
G-proteins Coupled Receptors
Animations <~ Watch this!
G-protein can activate an
enzyme OR an effector that will go on to
activate
Ions, larger compounds (Ex:
Ca2+, cAMP)
Ex: Calcium Pathway
Maintaining electrical potential across
membranes, cofactor for many enzymes
•Phosphorylation cascades amplify signal
•Activated enzymes induce a signal response
Receptor Protein Kinases
•Activity within cell altered by:▫Second
messengers
▫Phosphorylation cascades
3. Response
4. Deactivation•Built in systems to
“turn off”▫Hydrolyze GTP/ATP
▫Stop phosphorylation
▫Overstimulation