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 Lamella
2 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?
Close communication in ANIMALS!!!
• gap junctions – holes in ECM and
membrane specialized proteins admit:




H2O
aa’s
sugar
nucleotide
Coordinate reactions (Ex:
muscle contractions;
heartbeats)
Fig. 11-4
Plasma
membranes
Gap junctions
between animal cells
(a) Cell junctions
(b) Cell-cell
recognition
Plasmodesmata
between plant
cells
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 specific
2. Dynamic – overstimulation = adaptation
3. Potential blockage
1. PROCESS
• Upon receipt, response initiation begins
• 2 types:
1. Direct
hormone enters
binds to receptor
complex enters nucleus
binds to DNA
directs gene expression
2. Indirect
hormone binds to receptor
signal transduction begins
G-proteins
Receptor protein kinases
Both Pathways Result in:
1. Conversion of extracellular signal to intracellular message
2. Amplification of a message many times over
G-proteins Coupled Receptors
G-protein can
activate an
enzyme OR an
effector that will
go on to activate
Ions, larger
compounds (Ex:
Ca2+, cAMP)
Animations <~ Watch this!
Ex: Calcium Pathway
Maintaining
electrical
potential
across
membranes,
cofactor for
many
enzymes
Receptor Protein Kinases
• Phosphorylation
cascades amplify
signal
• Activated enzymes
induce a signal
response
3. Response
• Activity within
cell altered by:
▫ Second
messengers
▫ Phosphorylation
cascades
4. Deactivation
• Built in systems to
“turn off”
▫ Hydrolyze GTP/ATP
▫ Stop phosphorylation
▫ Overstimulation