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